تعیین ساختار پروتئین و ارزیابی سطح بیان ژن Tup1 قارچ Zymoseptoria tritici

نوع مقاله : پژوهشی- انگلیسی

نویسندگان

1 دانش آموخته دکتری بیماری شناسی گیاهی، دانشکده کشاورزی، دانشگاه تربیت مدرس، تهران ، ایران

2 استادیار گروه زیست فراورده های گیاهی، پژوهشکده بیوتکنولوژی کشاورزی، پژوهشگاه ملی مهندسی ژنتیک و زیست فناوری ، تهران، ایران

3 استاد بیماری‌شناسی گیاهی، دانشکدۀ کشاورزی، دانشگاه تربیت مدرس، تهران، ایران

4 دانشیار بیماری‌شناسی گیاهی، دانشکدۀ کشاورزی، دانشگاه تربیت مدرس، تهران، ایران

چکیده

مقدمه: قارچ  Zymoseptoria tritici بیمارگر دیمورفی است که تغییر در الگوی رشد آن نقشی اساسی در ایجاد بیماری دارد. به همین جهت، پروتئینTup1،که یک سرکوبگر رونویسی عمومی و تنظیم کننده شناخته شده ای برای تغییر شکل است، کاندیدای واجد شرایط برای مطالعه مقدماتی در این بیمارگر است.
مواد و روش‏‏ها: با استفاده از Saccharomyces cerevisiae Tup1p  بعنوان مدل، دومین­های عملکردی پروتئین با استفاده از نرم افزار InterPro (Pfam) ترسیم شد. سپس ساختار سوم Zt.Tup1p توسط نرم افزار  InterPro (Pfam)نشان داده شد. سرانجام ، میزان بیان Zt.Tup در شرایط in vitro  و in vivo توسط Real-Time RT-PCR ارزیابی شد.
نتایج: پروتئین Zt.Tup1p دارای ساختارهای عمومی موجود در در سایر پروتئین های یوکاریوتی شبهTup ، شامل دومین N-ترمینال، منطقه میانی محافظت نشده و یک دومین C- ترمینال با هفت تکرار WD است. همچنین نتایج نشان داد که دو المنت غنی از گلوتامین (Q1, Q2) موجود در S. cerevisiae، در ساختار Zt.Tup1p وجود ندارد. نتایج مشخص کردند که بیان ژن Zt.tup1 در مرحله میسلیومی افزایش می­یابد. بعلاوه افزایش بیان ژن در روزهای 14 و 24 بعد از تلقیح به گیاه نیز مشاهده شد.
بحث و نتیجهگیری: وجود هفت تکرار WD محافظت شده در Zt.Tup1p و سایر قارچ های مرتبط نشان می­دهد که این دومین­های عملکردی نقش مهمی در زندگی این میکروارگانیسم­ها دارند. با توجه به داده­های مطالعه حاضر، بیان بالای ژن Zt.tup1 در مرحله میسلیوم نشان می­دهد که این پروتئین ممکن است نقش مهمی در توسعه میسلیوم و تشکیل کونیدی داشته باشد.
علاوه بر این، افزایش بیان در زمان نکروتروفی که با توسعه پیکنیدی مشخص می شود، نشانگر این است که ژن ممکن است نقشی اساسی در رشد و بیماری­زایی Z. tritici داشته باشد.  مطالعه حاضر را می­توان بعنوان شروع یک نظریه پردازی جدید و جامع برای شفاف سازی عملکردهای دقیق این ژن در طول رشد و بیماری زایی در نظر گرفت.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Protein structure determination and evaluation of gene expression level of Tup1 from Zymoseptoria tritic

نویسندگان [English]

  • Elham Zamani 1
  • Forough Sanjarian 2
  • Ebrahim Mohammadi-goltapeh 3
  • Naser Safaie 4
1 Graduate Ph.D Student of Department of Plant pathology, Tarbiat Modarres University, Tehran, Iran
2 Plant Bioproducts Department, Institute of Agricultural Biotechnology (IAB), National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran., Iran,
3 Professor of Plant pathology Department of Plant Pathology, Tarbiat Modares University, Tehran, Iran
4 Associate Professor of Plant pathology, Department of Plant Pathology, Tarbiat Modares University, Tehran, Iran
چکیده [English]

Introduction: Zymoseptoria tritici is a dimorphic pathogenic fungus in which switching growth pattern plays a crucial role in diseases development. Therefore, Tup1 protein, the global transcriptional repressor which is a well-known regulator of dimorphism might be a qualified candidate for preliminary study in the pathogen.
Materials and methods: Using Saccharomyces cerevisiae Tup1p as a model, the functional domains of the protein were plotted using InterPro software. Then Zt.Tup1p tertiary structure were represented by accelrys DS visualize software. Finally, the in vitro and in vivo levels of expression of Zt.Tup were evaluated by real Time RT-PCR.
Results: Zt.Tup1p included public structures available in the other Tup1-like eukaryotic proteins, with an N-terminal domain, a poorly conserved middle region and a C-terminal domain with seven WD repeats. Also, the results showed that the two glutamine-rich elements (Q1 and Q2) contrary to which was identified in the S. cerevisiae, do not exist in Zt.Tup1p structure. The results were indicated that the expression level of Zt.tup1 up-regulate during mycelial stage. In addition, Zt.Tup1p was partly up-regulated in 14 and 24th post-inoculation.
Discussion and conclusion: The presence of seven conserved WD repeats in C terminal domain of Zt.Tup1p and the other related fungi indicates that these functional domains play an important role in the life of these microorganisms. According to the data of the present study, the up-regulation of Zt.tup1 gene during mycelial stage suggests that it may play a major role in mycelium development than in conidia formation. Furthermore, it’s up-regulation during necrotrophy which are characterized by the development of pycnidia shows that the gene may play a key role in the growth and pathogenicity of Z. tritici. The present study can be considered as promising new leads for starting a new comprehensive survey for clarifying this gene detailed functions during the development and pathogenicity.

کلیدواژه‌ها [English]

  • Expression level
  • Pathogenicity
  • Tup1
  • WD repeats
  • Zymoseptoria tritici

Introduction

In the fungi kingdom, dimorphism refers to the capacity to change the morphology between yeast-like growth and filamentous states (1). Growth in the yeast state refers to the production of two independent cells by mitotic divisions, budding or fission. In the filamentous state, two different models were described. In the first model, the pseudohyphal model, cells following cytokinesis become elongated. They, however, fail to separate and remain joined as chains of cells. In the second model, true hyphae with long continuous tubes are produced, then nuclei separate in the tubes. Increasing evidence has shown that pathogenic fungi use this ability to manage growth between saprophytic and pathogenic forms (2). This morphological switch occurs in response to many environmental stimuli and the role of two cAMP and MAPK signaling pathways in regulating dimorphism has been verified (1, 3, 4).

Tup1, the global transcriptional repressor is a well-known regulator that controls dimorphism and has conserved status in evolutionarily distant organisms (5). In Saccharomyces cerevisiae, the model yeast, the mechanism of action, and the structure of Tup1p were studied comprehensively. In this yeast, Tup1p associates with Ssn6 (Cyc8) and forms the Ssn6-Tup1 transcriptional co-repressor complex consisting of four monomers of Tup1 and one monomer of Ssn6. Ssn6p is a protein with tetratricopeptide repeat (TPR) motifs that mediates protein-protein interactions (6). None of these proteins have a DNA binding region and their role was played by interaction with specific DNA-binding transcription factors (7). Tup1–Ssn6 is required for the transcriptional repression of more than 300 genes under standard growth conditions (8). A wide variety of gene families contain at least nine groups: glucose repressible genes (9), mating type regulated genes (10), Nucleo DNA damage-inducible genes (11), oxygen-regulated genes (12), Osmo stress-inducible genes (13), a fatty acid regulated gene (14), flocculation-related genes (15), sporulation-related genes (16), and a meiosis-related gene (17) which can be regulated by this complex.

Several studies showed that three functional domains with diverse impose on transcription regulation were defined for Tup1 protein in budding yeast. The first domain, N- terminal is a region with 72 amino acids (aa), the C-terminal has seven WD repeats (340–713 aa), and the middle region is between two parts. The N-terminal is involved in the interaction with Ssn6 and the formation of the co-repressor complex (18). It also mediates oligomerization (19). The middle region is involved in repression as well as interaction with the N-terminal of histones. This region is located at 73–385 and amino acids 120–316, and has a high affinity for binding to H3 and H4 histones (20) and provides molecular evidence for direct interaction between the Ssn6-Tup1 complex and chromatin organization. It was pointed out that in the middle region, the Tup1 histone-binding domain corresponded to the repression domain (21). According to another study (22), there are two independent repression domains, one in 73–200 aa and the other within 288–389 aa as suggested. Some studies suggested that Tup1p has two repression domains, one in the N-terminal which contains the Ssn6-association region, and the other in the C-terminal, in a region overlapping with the first WD repeats (7). Therefore, the histone binding region overlaps with two repression domains located in N- and C-terminals. The WD40 repeats domain, located in the C-terminal region, forms a highly conserved protein-protein interaction domain (20). Each WD repeat is a 40-amino-acid motif that possesses a highly-conserved tryptophan-aspartate or WD sequence. This motif was found in proteins and it often physically interacts with other proteins and functions as a scaffold in multimeric complexes construction (23). Proteins with WD repeats are involved in a wide variety of processes, including gene repression, signal transduction, secretion, RNA splicing, and progression through the cell cycle (24). According to this description, Lamas-Maceriras et al. (25) identified four functionally important domains in Tup1 protein in S. cerevisiae. In animal pathogenic fungi, the function of Tup1p as one of the best-known regulators of dimorphism was investigated but its role in most plant pathogenic fungi is unknown (26).

Zymoseptoria tritici is one of the most important fungal pathogens in wheat (27). This fungus causes septoria tritici blotch (STB), a destructive disease of wheat (28). Z. tritici is a dimorphic pathogen with two filamentous and yeast-like states. This switch in growth pattern plays an important role in the entry of the pathogen into the infection cycle (29). The identification and functional analysis of effectors can produce precise knowledge for disease management techniques (30). Therefore, various studies were dedicated to reveal molecular aspects of dimorphism and pathogenicity in Z. tritici with an emphasis on effectors discovery. Now, the critical role of different components of two cAMP and MAPK signaling pathways in this field has been verified (31-33) and these investigations are still ongoing (34, 35).

In the present study, the sequence and structure of Tup1p of Z. tritici as an eligible candidate were studied. The survey was conducted by studying Tup1p from S. cerevisiae as the model organism and some dimorphic, plant pathogenic fungi. The presence of identified domains and the amount of their conservation were examined and the secondary structure of the protein was predicted. Finally, the best tertiary structure was drawn and presented and the expression profile of Tup1p in Z. tritici was examined in conidial and mycelial stages at different time points of the infection cycle in the greenhouse assay.

Materials and Methods

Species and Accession Numbers: Tup1p sequences of four plant pathogenic and dimorphic filamentous fungal species including Z. tritici IPO323 (Tup1, XP_003850038), Verticillium dahlia (rco-1, EGY14823), Ustilago maydis (Tup1, EAK84267), and Claviceps pupurea (rco-1, AAB63195) and three dimorphic yeast species including S. cerevisiae (Tup1p, AAA35182), Candida albicans (Tup1, AAB63195), and S. pombe (Tup1, AAB81475) were used for multiple alignment analysis. Tup1 sequence in U. maydis was provided from MIPS U. maydis Database (http://mips.gsf.de/genre/proj/ustilago/). V. dahlia Tup1 sequence was obtained from Verticillium group database (http://www.broadinstitute.org/). C. albicans and S. cerevisiae Tup1 sequences were provided from CGD (http://www.candidagenome) and SGD (http://www.yeastgenome.org/), respectively. The rest of the Tup1 sequences were obtained from the NCBI (http://www.ncbi.nlm.nih.gov/) (Table1).

Table 1- The Studied Microorganisms and the Accession Number of Their Tup1

Ref.

Accession number

Microorganism

http://www.ncbi.nlm.nih.gov/

Tup1, XP_003850038

Z. tritici IPO323

http://www.broadinstitute.org/

rco-1, EGY14823

Verticillium dahlia

http://mips.gsf.de/genre/proj/ustilago/

Tup1, EAK84267

Ustilago maydis

http://www.ncbi.nlm.nih.gov/

rco-1, AAB63195

Claviceps pupurea

http://www.yeastgenome.org/

Tup1p, AAA35182

S. cerevisiae

http://www.candidagenome

Tup1, AAB63195

Candida albicans

http://www.ncbi.nlm.nih.gov/

Tup1, AAB81475

S. pombe

 

Sequence Analysis: The physicochemical characteristics of Z. tritici Tup1p were defined using a primary sequence and with the help of the ProtParam tool (http://web.expasy.org/protparam/).

Sequence Alignment, Phylogenetic Analysis, and Domain Structure: The detailed study of the Tup1 protein sequences in these fungi was performed using ClustalW2 for multiple sequence alignments and the InterProScan sequence search tool from the European bioinformatics institute (http://www.ebi.ac.uk/) was applied for domain structure analysis. The schematic diagram of the obtained domains using Pfam was presented after the analysis by keeping proportions of each domain according to the total length of the proteins. The phylogenetic analysis of full-length protein sequences was performed using MEGA5 software with the neighbor-joining method using default setting (36).

Prediction of Secondary and Tertiary Structure: Chou and Fasman secondary structure prediction (CFFSSP) server at http://www.biogem.org/tool/chou-fasman/, SOPMA software at http://npsa-pbil.ibcp.fr/cgi-bin/npsa_automat.pl?page=npsa_sopma.html, GOR software at http://npsa-pbil.ibcp.fr/cgi-bin/npsa_automat.pl?page=npsa_gor4.html, and the program JPred 3 (http://www.compbio.dundee.ac.uk/wwwjpred/) were employed to predict the secondary structure.

I-TASSER software at http://zhanglab.ccmb.med.umich.edu/I-TASSER/, LOMETS software at http://zhanglab.ccmb.med.umich.edu/LOMETS/, MUSTER software at http://zhanglab.ccmb.med.umich.edu/MUSTER/, and PHYRE http://www.sbg.bio.ic.ac.uk/~phyre/ software were employed for tertiary structure prediction. The profile of energy minimization was computed by Swiss-PdbViewer software. The AMPAGE database at http://mordred.bioc.cam.ac.uk/~rapper/rampage.php and Swiss-PdbViewer software were used for the detection of the structural stability of the proteins by Ramachandran plot.

The Expression Level of Zt.Tup1: To study the expression profile of Zt.Tup1 in conidial and mycelium phases, IPO323 was inoculated on yeast glucose broth and maintained in shaker-incubator at 15 and 25 °C, respectively, for five days at a speed of 125 rpm. Then, the samples were freeze-dried and used for RNA extraction. For greenhouse experiments, the susceptible wheat cultivar, Kavir, was used. Spore suspension of IPO323 was used for the inoculation of ten-day-old plants by using previously-used protocols (37). At 0, 4, 14, and 24 days after inoculation, three biological replications of the infected leaves were collected for RNA extraction. The total RNA isolation was done with RNX-Plus kit (Cinagene, Iran). Reverse transcription was performed using the RevertAid Reverse Transcriptase kit (Thermo Scientific, Germany) by the oligo-dT primer. For transcript quantification, the following primer pairs were designed, respectively:  for Tup1 and β-tubulin using the Primer3Plus online software (http://www. bioin forma tics.nl/prime rs3pl us): forward 5′-CACCTCCACAAGAGCAACAA -3′, reverse 5′- CTTGTCCTCCGCTCCTGTAG -3′ and Forward 5′-ACCATCTCCGGCGAACAT -3′, and reverse 5′-GGAATTCTCGACCAGCTGG -3′. The expression analyses of the Tup1 gene were carried out using SYBER Green qPCR Master mix (YTA, Iran) with Corbett RG-6000 Real-time PCR machine (Corbett Life Science, QIAGEN, Germany). Initially, the expression level of each sample was normalized with the β-tubulin gene and then the comparative Ct method was used to calculate the expression levels (38).

Results

Based on the results of the ProtParam tool, the atomic composition of Z. tritici Tup1p contains 9021 atoms comprising carbon (2860), hydrogen (4422), nitrogen (846), oxygen (871), and sulfur (22). Also, C2860H4422N846O871S22 has been retrieved as Zt.Tup1 molecular formula. The retrieved primary sequence of Z. tritici Tup1p has 603 amino acids, 65.299 kD molecular weight, and 6.44 theoretical pI. A majority of amino acids are present in the sequence including glycine (11.3%), proline (9.6%), alanine (7.6%), and glutamine (7.6%). Cysteine exhibited a minimum frequency (1.2%) of residue. The sequence included about 60 negatively-charged residues (Asp + Glu) and 54 positively-charged residues (Arg + Lys). The aliphatic index and the instability index were calculated as 65.52 and 43.98, respectively. This tool graded the protein as unstable and the grand average of hydropathicity (GRAVY) was -0.579.

The result of multiple sequence alignments and domain structure analyses of Tup1 proteins from these fungi are shown in Fig. 1 (and Sup 1). The three main and functionally-identified domains of Tup1p structure in S. cerevisiae as a model yeast (18) are shown in Fig. 1A (and Sup 1): (i) N-terminal region contains 72 amino acids and is involved in complex formation with Ssn6 and formation of the oligomeric state of Tup1p; (ii) middle region (residues 73–385) contains different parts: two repression domains (R1 and R2) that have the ability to interact with other factors, two glutamine regions (Q1 and Q2) and one ST-rich domain; and (iii) C-terminal region with seven WD repeats that are involved in the interaction with other proteins and it is shown that the first WD repeat partially overlaps with R2 repression domain.

Based on S. cerevisiae, these domains include the Tup_N domain in the amino-terminal region, seven WD40 domain repeats in the carboxyl-terminal region, and a poorly-conserved middle region.

Tup1p sequence similarity in Z. tritici and S. cerevisiae was 39.66 % (Sup 2). Among the sequences examined, Tup1p sequence of C. purpurea has the highest similarity with Z. tritici Tup1p (60.76%).

The phylogenetic analysis of full-length protein sequences showed that the sequences sort into two clades, one of them includes plant pathogenic species and the other includes yeast species (Fig. 2). The topology of the clades showed the closest relationship between the V. dahlia and C. purpurea sequences in the first clade and S. cerevisiae and C. albicans in the second clade.

The secondary structural analysis of the protein was done.  The random coil is the most frequent (62.02%), followed by an extended strand (21.56%) and finally Alpha helix as being the least frequent (16.42%) (Table 2). The dominance of the coiled regions indicates the high level of conservation and stability of the protein structure (39).

Since the factor exerts its numerous effects through complex and multiple interactions, it was necessary to perform further investigations to show the presence of the characterized domains and motifs. The1–72 residues in the N-terminal region of Tup1p are required for the organization of both Tup1-Ssn6 complex and oligomeric status of Tup1 (22). In Zt.Tup1p, a partly-conserved helix structure is formed in the secondary structure at positions 1-72 (these residues are indicated with h in Sup 3.). Two glutamine-rich elements (Q1 and Q2) described in Sc.Tup1 p (25) were not present in Zt.Tup1p. Therefore, the region 1–72 of Zt.Tup1p did not conserve in the major part of the sequence. Also, the sequence covering positions 96–116 lacked the α-helical structure and the Q1-rich element. This indicated the structural difference in this part of the sequence which included a repression-associated region that has not been previously reported. Considering that Zt.Tup1 N-terminus did not have a high similarity with Sc.Tup1p, we tried to compare the sequence among filamentous fungi species used in this study (Sup 3).

 

Fig. 1- A) The characterized functional domains of Tup1p in Saccharomyces cerevisiae are shown in this diagram (adapted by Lamas-Maceiras et al.(25)). B) The comparison of the conserved domains of Tup1 proteins among different fungi species. The conserved structure of Tup1 proteins in S. cerevisiae (Sc.Tup1), Zymoseptoria tritici (Zt.Tup1), Candia albicans (Ca.Tup1), Saccharomyces pombe (Sp.Tup1), and Ustilago maydis (Um.Tup1), Verticillium dahlia (Vd. rco-1), and Claviceps purpurea (Cp. rco-1). The domains were depicted with the comparison to functionally characterized-domains of S. cerevisiae using InterPro (Pfam) software. All domains described for Sc.Tup1 are available in the rest and include the N-terminal Tup_N domain (green square), seven WD40 domains in the C-terminal region (red squares), and a less-conserved middle region.

Fig. 2- Dendrogram of Tup1p protein in different species, based on ClustalW alignment of full-length translated protein sequences

Table 2- Secondary Structure Elements of the Zt.Tup1p

Structural elements

Number of residues

Percentage of residues

Alpha helix     (Hh)

99

16.42%

310 helix      (Gg)

0

0.00%

Pi helix        (Ii)

0

0.00%

Beta bridge     (Bb)

0

0.00%

Extended strand (Ee)

130

21.56%

Beta turn       (Tt)

0

0.00%

Bend region     (Ss)

0

0.00%

Random coil     (Cc)

374

62.02%

Ambiguous states (?)

0

0.00%

Other states

0

0.00%

 

The results indicated that the secondary structure of Um.Tup1p had a significant difference with the rest of the sequences. On the other hand, Zt.Tup1p, Cp. Rcor-1 and Vd. Rcor-1 showed a high similarity in this region. The multi-alignment analysis Tup1p homologous in these fungi revealed that they did not have R1 and R2 regions with the same sequences which were observed in Sc.Tup1p. ST region and also Q1 and Q2 sequences did not exist but Vd. Rcor-1 had one Q-rich region in 168-183 (Sup. 1).

The carboxy-terminal region of Tup1 protein is an important fragment in protein-protein interaction. Tup1p appertains to the WD family of eukaryotic proteins specified by having a conserved region with seven repeats named WD40 motifs. This repeat is a degenerate one known as a beta-transducin repeat. WD40 is a variable region in both length and composition with approximately 40 amino acids and contains a core region with a uniform length. It was suggested that proteins containing WD40-repeats have a variety of functions such as signal transduction, transcription regulation, cell cycle control, autophagy, and apoptosis (40). The common function of all WD40-repeat units is to provide a rigid scaffold for protein interactions and to form multi-protein complexes. The results showed high conservation in the amino-acid sequences of this region. Also Zt.Tup1p, Cp.Rcor-1 and Vd.Rcor-1 C-terminus comparison showed that all three sequences had a high similarity and conservation in seven WD repeats (Fig. 1 and Sup. 1). 

All the generated tertiary structures by I-TASSER, LOMETS, MUSTER of the Zt.Tup1 protein models were subjected to a series of tests for assaying their internal consistency and reliability. The result of the structural stability test of the obtained best tertiary structure by Ramachandran plot is shown in Fig. 3.

According to this test, 94.7% of the residues are located in a favored region. Also, 4.3% and 1% of the residues are located in allowed and outlier regions, respectively. Zt.Tup1p tertiary structures were depicted by the Accelrys Ds visualize software and is shown in Fig. 4.

Fig. 3- Ramachandran plot of the best tertiary structure of Zt.Tup1p

Evaluating Zt.Tup1 transcriptional level, higher expression was observed in the mycelia stage in comparison with the conidial stage (Fig. 5). In planta, the expression profile corresponded remarkably well with the early stage of infection or biotrophic phase (4 dpi) and also the necrotrophic phase (>8 dpi, Fig. 5).

Fig. 4- Zt.Tup1p tertiary structure depicted by the Accelrys DS visualizer software

 

Fig. 5- Transcript levels of Zt.Tup1 in conidial and mycelium phases and during infection or biotrophic phases as detected by RT-qPCR.  Error bars represent the standard error (N = 3). Normalization of reads was done with respect to the β-tubulin as a reference gene.

Discussion and Conclusion

In Z. tritici as a phytopathogenic ascomycetea, the switch from yeast-like growth to a filament phenotype plays a critical role in the infection cycle of the pathogen. This process occurs in response to different environmental stimuli and is highly controlled by complex genetic pathways (41, 42).

The Zt.Tup1p and Tup1p of other filamentous fungi studied in this paper contained most of the identified functional domains of Sc.Tup1p. Also, the complete sequence comparison showed that they had a different degree of sequence similarity. In other words, they include public structures available in the other Tup1-like eukaryotic proteins, with an N-terminal domain, a poorly-conserved middle region, and a C-terminal domain with seven WD repeats. Overall, despite the differences in the sequence, the structure of functional domains was preserved in all studied proteins. These results indicate that these functional domains have been preserved during the evolution due to their critical importance (18).

The amino acid residues of 72 N-terminal are involved in a complex formation with Ssn6. It was suggested that Ssn6 may play the role of an adapter between Tup1p and DNA-bound proteins (43). The formation of two α-helical segments in the first 72 amino acids of Zt.Tup1p was confirmed showing that the Ssn6 interaction domain is conserved. Considering that in the Zt.Tup1p sequence, Q1 region (residues 96–116) is not conserved, Q2 (residues 173–194) is not present, the α-helix predicted in this segment is not formed in the Zt.Tup1p structure. Furthermore, contrary to what was identified in S. cerevisiae, the N-terminal domain comparison between Zt.Tup1p and the other filamentous fungi showed that most of them do not have two glutamine-rich elements (Q1 and Q2). Probably, in pathogenic filamentous fungi, this sequence does not have virulence effects, but confirmation of this hypothesis needs further research.

Although the R1 repression domain was not conserved among these filamentous fungi, R2 was partly conserved. Lamas-Maceiras et al. suggested that this difference could have several effects on the structure and function of the protein since the amino acid sequence (residues 96–116) may have other roles or such changes may create a new capability in repression responses and ultimately may be ineffective in protein function (25).

The crystal structure of the Tup1p WD domain has been characterized. This structure confirmed that the seven repeated units create a propeller-like figure with seven blades in which each blade is made up of four β strands (43, 44). The study showed that WD repeats in C-terminus are available and highly conserved in Zt.Tup1p and other filamentous fungi. WD domain is responsible for transcriptional repression and protein-protein interactions. The ST sequences of the middle region (residues 365–385) between WD1 and WD2 are not present in the filamentous fungi studied in this research. Zhang et al. found that the deletion of the ST region in S. cerevisiae Tup1p did not show loss of repression. They suggested that this region may be unique to yeasts Tup1p and is not present in other higher eukaryotic homologs nor is important for repression (18).

The phylogenetic analysis of full-length protein sequences showed that the sequences are divided into two clades:  one includes plant pathogenic species and the other one includes yeast species. The topology of the clades showed the closest relationship between the V. dahlia and C. purpurea sequences in the first clade as well as S. cerevisiae and C. albicans in the second clade. Considering these results, it seems that the filamentous fungal and yeast species in evolutionary terms have two separate paths. During the course of evolution, mutations occurred for better fitness and these changes led to the separation of filamentous fungi and yeasts in phylogenetic studies.

As mentioned earlier, Tup1 protein is known for its role in dimorphism. In the present study, Zt.Tup1 expression was examined in two stages of the fungal life cycle that are associated with transformation.

The expression of the gene was evaluated in both conidial and mycelia stages as well as different post-inoculation time points during the pathogenic interaction with wheat. According to the results of the present study, the up-regulation during the mycelial stage suggests that Zt.Tup1p may play a major role during mycelium development. During the stage of infection, low expression was found in the first-time point. Subsequently, the expression was strongly induced (about 20-fold) during biotrophy at 4 dpi and then constantly decreased until 24 dpi. In addition, Zt.Tup1 was partially up-regulated during necrotrophy at 14 and 24 dpi. These findings show that Zt.Tup1p may play a key role in the pycnidium development.

Overall, the expression profiling suggested that Tup1 may play a fundamental role in Z. tritici growth and development. Contrary to Chen et al.’s study on Magnaporthe oryzae, the authors of the present study observed a higher transcript level for Tup1 in the mycelia stage (45). However, it was proved that Mo.Tup1 is essential for vegetative growth and correct hyphal branching. Even though the role of Tup1p in fungal dimorphism seems conserved, the control pathways associated with this process frequently differed among fungi (26). Roldán et al. stated that the role of Tup1p in the regulation of morphological changes in many plant pathogenic fungi is partly unknown (46).

In summary, the present study provided basic information on the structure and function of the Zt.Tupl p. It is expected that these results could be useful in the development of new pathogen management strategies and could be an initial step for further research on the role of this protein in the mechanisms of pathogenicity in Z. tritici.

Acknowledgments

This work was supported by the National Institute of Genetic Engineering and Biotechnology and Tarbiat Modares University, Tehran, Iran.

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Sp.Tup1       ------------------------------------------------------------     0

Sc.Tup1       ------------------------------------------------------------     0

Ca.Tup1       ------------------------------------------------------------     0

Um.Tup1       MYSHRSIVPSAGSQGPPSGPPPPGPGGAGPSQAAAAAAAAAAAAAAQQAPHPGGPVAGGP     60

Zt.Tup1       ------------------------------------------------------------     0

Vd.Rco-1      ------------------------------------------------------------     0

Cp.Rco-1      ------------------------------------------------------------     0

                                                                         

 

Sp.Tup1       -------------------------------VNELLEAVKKEFEDICQKTKTVEAQKDDF     29

Sc.Tup1       --------------------MTASVSNTQNKLNELLDAIRQEFLQVSQEANTYRLQN-QK     39

Ca.Tup1       ------------MS------MYPQRTQHQQRLTELLDAIKTEFDYASNEASSFK-KV-QE     40

Um.Tup1       GGPAPTGPPGAAPGPPGAAPPAGAPHTGSARLADLLDFVRHEFDLLGNDTAQFKA-Q-RD     118

Zt.Tup1       --------------MYNAHRGMAPGPQPGSRLADLLEQVRAEFDAQVGR---------SS     37

Vd.Rco-1      -------------------MGGAAPPVNQSRLEELLEQIRTEFSSQSRT---------TE     32

Cp.Rco-1      ------------MSMYSHRGMGAVPLGNSGRLNELLDQIRAEFETQLRQ---------TE     39

                                             : :**: :: **                

 

Sp.Tup1       EYKAMISAQINEMALMKQTVMDLEMQQSKVKDRYEEEITSLKAQLEARRKEIASGVVPQS     89

Sc.Tup1       DYDFKMNQQLAEMQQIRNTVYELELTHRKMKDAYEAEIKHLKLGLEQRDHQIASLTVQQQ     99

Ca.Tup1       DYDSKYQQQAAEMQQIRQTVYDLELAHRKIKEAYEEEILRLKNELDTRDRQMKNGFQQQQ     100

Um.Tup1       EMEHRVTSQVSEVNMMQTHFYELEKRHTQIIQQYEEEVKRLRSILDSRGLSSEH-GAASA     177

Zt.Tup1       DHEHQLHNQIQEMDVIKSKIYQLETTHVAMKNKYEEEIARLRHELEQRGGPSQ------G     91

Vd.Rco-1      AYEHQIQAQVSEMQHVREKVFNMEQMHLNLKQKYEEELAHLRRQLEISRGGNAPPGMNSG     92

Cp.Rco-1      GFEHQISAQVSEMQLVREKVYAMEQTHMTLKQKYEEEISMLRHQLENSRKGGPQPGMP-G     98

                .     *  *:  ::  .  :*  :  : : ** *:  *:  *:             

 

Sp.Tup1       SKTKHGRNSVSFGKYGNAGPFNSDNSSKPLILNNGSSGGTPKNLRSPAIDSDGTVLAPIQ     149

Sc.Tup1       QQQQQQQQVQQHLQQ-QQQQLAAASASVPVA------QQPPA-TTS-------ATATPAA     144

Ca.Tup1       QQQQQQQQQQ---QQ-QQQQIVAPPAA------------PPA------------------     126

Um.Tup1       T--------GPMSGP-PHLPASATSGPLPIA----SAGGPPP-PGGPGGAGSAAMFGPNG     223

Zt.Tup1       P--------HGASSS-QPAPPAIGH--------------------GPANLFQGIMAGGAG     122

Vd.Rco-1      P--------PPHNAP-SQQPPSIPS--------------------G-NGLFNGIMAGGGQ     122

Cp.Rco-1      P--------PQHAGP-SQQPPSIAP--------------------G-NGLFSGIMTGSNQ     128

                                                                         

 

Sp.Tup1       TSNVDLGSQYYSSPHVRPAVGATMAGSAMRTFPSNLPLG---------------------     188

Sc.Tup1       --NTTTGSPSAFPV---QASRPNLVGSQLPTT----TLPVVSS------NAQQQLPQQQL     189

Ca.Tup1       ------------------------------------------------------------     126

Um.Tup1       --NGALGG----------------PGSEYGRGPNGFDREREPPRGPTPGGKDS--KRMRV     263

Zt.Tup1       --GPGLAP-----PPQEQQGQPGMPGHMQGQMPPSLNAPPGPPHNP---FAYG-------     165

Vd.Rco-1      ---GGLAPP---PPPQDQQMGP--QQHQMPQGPPGLPAPPPPPPPQSQPPHFQQQQQQQQ     174

Cp.Rco-1      ---AGLAPPQQHPPPQEQQMGP--Q-HQMAQGPPGLPVPPPHPN----------------     166

                                                                         

 

Sp.Tup1       ------------------------------------------------------------     188

Sc.Tup1       QQQQLQQQQPPPQVSVA--PLSNTAINGSPTSKETTT-----LPSVKAPESTLKETEPEN     242

Ca.Tup1       ---------PPT-------P----------------------------------------     130

Um.Tup1       EGPASHYSGPPSPGPERERDWIKKEERGDRGPPPRADEKWDRDQRVGGGAH---------     314

Zt.Tup1       -----QLQGP---------P--AANGYGSQQPPQPTASPGPGKPRLGGPPGLRGPATPQQ     209

Vd.Rco-1      QQQQQQQQQPPQQAPYPQGP--VPGGIG-AQPPQSTASPGPGRRGIGRPPGGVGPATPQI     231

Cp.Rco-1      ------AQQPPYQGGYPQGP--VSNGMG-PQPPQSTASPGPGRRGVGRPPNVGGPATPQI     217

                                                                         

 

Sp.Tup1       ------------------HPPPPSDSANSSVT-----PIAAPLVVN-------GKV----     214

Sc.Tup1       NNTSKINDTGSATTA---TTT-----TATETEIKPKEEDATPASLHQDHYLVPYNQRANH     294

Ca.Tup1       --------------------------------------VTSLSVIDKSQYIVNPTQRANH     152

Um.Tup1       ------LGPGPVQSPHGAPPLPPSNLYNRDMHRDARDRDSRPSEVASA--DSPGAAAAAA     366

Zt.Tup1       HPAS--TYPGSPQ---VARPTPPPNRD---------------VQIAT---D--FQYTPAQ     244

Vd.Rco-1      NTPI--PFPGATQSPQVSHPTPDHARM-----------------------G--NPHPPPP     264

Cp.Rco-1      NTPV--PYSGNAQSPQVSHPTPDHGRM-----------------------G--GPR----     246

                                                                         

 

Sp.Tup1       -SGNPPYPAEI--IPTSNVPNREEKDWTVTSNVPNKEPPISVQLLHTLEHTSVICYVRFS     271

Sc.Tup1       SKPIPPFLLDLDSQSVPDALKKQTNDYYILYN-PALPREIDVELHKSLDHTSVVCCVKFS     353

Ca.Tup1       VKEIPPFLQDLDIAKANPEFKKQHLEYYVLYN-PAFSKDLDIDMVHSLDHSSVVCCVRFS     211

Um.Tup1       GNVTLASLSDMDPDEIPKELKKEGPDWLAIFN-PKVKRTLDVNLVHTFLHESVVCCVRFS     425

Zt.Tup1       LEQIGNQLSEYDVDKLPPHLKRQGDDWFAVFN-PRVHRKLDVELVHSLPHQSVVCCVRFS     303

Vd.Rco-1      APPVGNALGDLDIDRLPSSAKKSGYDWFVVYN-ERVPRMIDVDLVHTLGHESVVCCVRFS     323

Cp.Rco-1      VPPVGNALAELDLDSVAPHHKKTGSDWYAIFN-PSVQRVLDVDLVHSLAHESVVCCVRFS     305

                       :          ::   ::    *       :.::: ::: * **:* *:**

 

Sp.Tup1       ADGKFLATGCNRAAMVFNVETGKLITLLQEESSK--------------------------     305

Sc.Tup1       NDGEYLATGCNKTTQVYRVSDGSLVARLSDDSAANNHRNSITENNTTTSTDNNTMTTTTT     413

Ca.Tup1       RDGKFIATGCNKTTQVFNVTTGELVAKLIDESSNENK-----------------------     248

Um.Tup1       ADGKYLATGCNKSAQIFDTKTGAKTCVLTDQS-AN-------------------------     459

Zt.Tup1       HDGRFIATGCNRSAQIFDVNTGKQVCHLMDQS-TN-------------------------     337

Vd.Rco-1      HDGKYVATGCNRSAQIYDVQTGEKLCILQDET-AD-------------------------     357

Cp.Rco-1      YDGKYVATGCNRSAQIYDVQSGEKVCVLEDHNAQD-------------------------     340

               **.::*****::: :: .  *     * :..                           

 

Sp.Tup1       --------------------------REGDLYVRSVAFSPDGKYLATGVEDQQIRIWDIA     339

Sc.Tup1       TTITTTAMTSAAELAKDVENLNTSSSPSSDLYIRSVCFSPDGKFLATGAEDRLIRIWDIE     473

Ca.Tup1       ---------------------DDNTTASGDLYIRSVCFSPDGKLLATGAEDKLIRIWDLS     287

Um.Tup1       --------------------------SKGDLYIRSVCFSPDGKCLATGAEDRQIRIWDIG     493

Zt.Tup1       --------------------------GDGDLYIRSVCFSPDGRYLATGAEDKIIRVWDIG     371

Vd.Rco-1      --------------------------VSGDLYIRSVCFSPDGKYLATGAEDKLIRT----     387

Cp.Rco-1      --------------------------MTADLYIRSVCFSPDGRYLATGAEDKLIRVWDIA     374

                                          .***:***.*****: ****.**: **    

 

 

Sp.Tup1       QKRVYRLLTGHEQEIYSLDFSKDGKTLVSGSGDRTVCLWDVEAGEQKLILH---------     390

Sc.Tup1       NRKIVMILQGHEQDIYSLDYFPSGDKLVSGSGDRTVRIWDLRTGQCSLTLS---------     524

Ca.Tup1       TKRIIKILRGHEQDIYSLDFFPDGDRLVSGSGDRSVRIWDLRTSQCSLTLS---------     338

Um.Tup1       KKKVKHLFSGHKQEIYSLDYSKDGRIIASGSGDKTVRIWDVENGQLLHTLYTSPGLEHGP     553

Zt.Tup1       AKVIRHQFSGHDQDIYSLDFASDGRYIASGSGDRTIRIWDLQDNQCVLTLS---------     422

Vd.Rco-1      -RTIRNTFSGHEQDIYSLDFARDGRTIASGSGDRTVRLWDIEPGSNTLTLT---------     437

Cp.Rco-1      SRSIRNHFSGHEQDIYSLDFARDGRTIASGSGDRTVRLWDIETGSNTLTLT---------     425

               : :   : **.*:*****:  .*  :.*****::: :**:.  .    *         

 

Sp.Tup1       TDDGVTTVMFSP-DGQFIAAGSLDKVIRIWTS-SGTLVEQLH-------GHEESVYSVAF     441

Sc.Tup1       IEDGVTTVAVSPGDGKYIAAGSLDRAVRVWDSETGFLVERLDSENESGTGHKDSVYSVVF     584

Ca.Tup1       IEDGVTTVAVSP-DGKLIAAGSLDRTVRVWDSTTGFLVERLDSGNENGNGHEDSVYSVAF     397

Um.Tup1       SEAGVTSVSISS-DNRLVAAGALDTLVRVWDAQTGKQLERLK-------SHKDSIYSVSF     605

Zt.Tup1       IEDGVTTVAMSP-NGRFVAAGSLDKSVRIWDTRSGVLVERTEG----EQGHKDSVYSVAF     477

Vd.Rco-1      IEDGVTTVAISP-DTKYVAAGSLDKSVRVWDIHQGYLLERLEG----PDGHKDSVYSVAF     492

Cp.Rco-1      IEDGVTTVAISP-DTQYVAAGSLDKSVRVWDIHSGFLVERLEG----PDGHKDSVYSVAF     480

               : ***:* .*  : : :***:**  :*:*    *  :*: .       .*::*:*** *

 

Sp.Tup1       SPDGKYLVSGSLDNTIKLWELQCVSNVA----PSMYKEGGICKQTFTGHKDFILSVTVSP     497

Sc.Tup1       TRDGQSVVSGSLDRSVKLWNLQNANN----KSDSKTPNSGTCEVTYIGHKDFVLSVATTQ     640

Ca.Tup1       SNNGEQIASGSLDRTVKLWHLEGKS-----------DKKSTCEVTYIGHKDFVLSVCCTP     446

Um.Tup1       APDGKSLVSGSLDKTLKLWDLTGTAKAVQENRAEEKGGHANCATTFVGHKDYVLSVSCSP     665

Zt.Tup1       SPDGEHLVSGSLDKTIRMWRLNPRAQYQPGS-LAPQARGGDCVRTFEGHKDFVLSVALTP     536

Vd.Rco-1      SPNGKDLVSGSLDKTIKMWELSTPR----GL-PNPGPKGGRCVKSFEGHRDFVLSVALTP     547

Cp.Rco-1      SPNGKDLVSGSLDRTIKMWELISPR----GG-QSAAPKGGKCVKTFDGHRDFVLSVALTP     535

              : :*: :.*****.::::* *                  . *  :: **:*::***  :

 

Sp.Tup1       DGKWIISGSKDRTIQFWSPDSPHSQLTLQGHNNSVISVAVS------PNGHCFATGSGDL     551

Sc.Tup1       NDEYILSGSKDRGVLFWDKKSGNPLLMLQGHRNSVISVAVANGSSLGPEYNVFATGSGDC     700

Ca.Tup1       DNEYILSGSKDRGVIFWDQASGNPLLMLQGHRNSVISVAVSLNSK--GTEGIFATGSGDC     504

Um.Tup1       DGQWVASGSKDRGVQFWDPKTAQAQFVLQGHKNSVIAINLS------PAGGLLATGSGDF     719

Zt.Tup1       DGAWVMSGSKDRGVQFWDPVTGDAQLMLQGHKNSVISVAPS------PMGTLFATGSGDM     590

Vd.Rco-1      DAAWVMSGSKDRGVQFWDPRTGATQLMLQGHKNSVISVAPS------PTGGYFATGSGDM     601

Cp.Rco-1      DANWVLSGSKDRGVQFWDPRTGSTQLMLQGHKNSVISVAPS------PQGGYFATGSGDM     589

              :  :: ****** : **.  :    : ****.****::  :           :******

 

Sp.Tup1       RARIWSYEDL---        561

Sc.Tup1       KARIWKYKKIAPN        713

Ca.Tup1       KARIWKWTKK---        514

Um.Tup1       NARIWSYDRISN-        731

Zt.Tup1       KARIWRYAPYGGP        603

Vd.Rco-1      RARIWSYRSLQ--        612

Cp.Rco-1      KARIWSYRPY---        599

              .**** :     

Sup.1- Results of alignment of Tup1 protein sequences from Saccharomyces pombe (Sp. Tup1), Saccharomyces cerevisiae (Sc.Tup1), Candida albicans (Ca. Tup1), Uromyces maydis (Um. Tup1), Zymoseptoria triciti (Zt.Tup1) and Verticillium dahlia (Vd. Rco-1) and Claviceps purpurea (Cp. Rco-1) by ClustalW with the following domains: N-terminal (residues 1–72) is in bold; middle region includes: two repression domains (R1and R2: residues 73–172 and residues 267–365 respectively) in gray; two glutamine-rich regions (Q1 and Q2: residues 96–116 and 173–194 respectively) are in bold and italics; and the ST domain (serine-threonine-rich region: residues 392–419) is placed in gray box. C-terminal (residues 317–682) with seven WD40 repeats are in open boxes and the S. cerevisie WD residues are in black boxes.

 

Sup. 2- Percent identity matrix between Tup1 protein from various fungi (created by Clustal2.1)

 

Verticillium dahlia

Candida purpurea

Zymoseptoria tritici

Ustilago maydis

Claviceps albicans

Saccharomyces cerevisiae

Saccharomyces pombe

Verticillium dahlia

100.00

78.35

59.72

44.98

48.73

40.30

43.42

Claviceps purpurea

78.35

100.00

60.76

46.45

50.00

42.52

43.98

Zymoseptoria tritici

59.72

60.76

100.00

45.73

48.86

39.66

42.12

Ustilago maydis

44.98

46.45

45.73

100.00

41.78

34.08

38.85

Candida albicans

48.73

50.00

48.86

41.78

100.00

66.41

44.26

Saccharomyces cereviciae

40.30

42.52

39.66

34.08

66.41

100.00

37.95

Saccharomyces pombe

43.42

43.98

42.12

38.85

44.26

37.95

100.00

                 

 

1

70

Sc. Tup1

Zt. Tup1

Vd. Rcor-1 

Cp. Rcor-1

Um. Tup1

71

140

Sc. Tup1

Zt. Tup1

Vd. Rcor-1 

Cp. Rcor-1

Um. Tup1

 

Sup. 3- Predicted secondary structure of the N-terminus in Saccharomyces cerevisiae, Zymoseptoria tritici, Verticillum dahlia, Claviceps purpurea and Ustilago maydis Tup1 proteins sequences (residues 1–72 and 73–128). The line HELIX shows residues likely to adopt a-helical structure.