Deletion of ptn1, a PTEN/TEP1 Orthologue, in Ustilago maydis Reduces Pathogenicity and Teliospore Development

Abstract

The PTEN/PI3K/mTOR signal transduction pathway is involved in the regulation of biological processes such as metabolism, cell growth, cell proliferation, and apoptosis. This pathway has been extensively studied in mammals, leading to the conclusion that PTEN is a major tumor suppressor gene. PTEN orthologues have been characterized in a variety of organisms, both vertebrates and non-vertebrates, and studies of the associated PTEN/PI3K/mTOR pathway indicate that it is widely conserved. Studies in fungal systems indicated a role of PTEN in fungal defense mechanisms in Candida albicans, and in the developmental process of sporulation in Saccharomyces cerevisiae. The present study was aimed at investigating the role of the PTEN ortholog, ptn1, in Ustilago maydis, the pathogen of maize. U. maydis ptn1 mutant strains where ptn1 gene is deleted or overexpressed were examined for phenotypes associate with mating, virulence and spore formation. While the overexpression of ptn1 had no substantial effects on virulence, ptn1 deletion strains showed slight reductions in mating efficiency and significant reductions in virulence; tumor formation on stem and/or leaves were severely reduced. Moreover, tumors, when present, had significantly lower levels of mature teliospores, and the percent germination of such spores was similarly reduced. Thus, ptn1 is required for these important aspects of virulence in this fungus.

A homologue of the mammalian tumour suppressor protein PTEN is a functional lipid phosphatase and required for chemotaxis in filamentous fungi

“…Both tepA deletion and overexpression strains were found to be indistinguishable from WT in their hyphal growth rate and colony morphology, a result similar to what has been observed for deletion of this gene in F. graminearum and U. maydis (Vijayakrishnapillai et al, 2018;Zhang et al, 2010). TEM analysis revealed that the S. pombe tep1 deletion mutant has an abnormal vacuolar morphology, highlighting the subtle nature of some culture phenotypes (Mitra et al, 2004).…”

“…In previous studies, deletion of the PTEN homologues in F. graminearum and U. maydis resulted in a decrease in virulence on wheat and maize, respectively (Vijayakrishnapillai et al, 2018;Zhang et al, 2010). Here we found that L. perenne plants infected with the tepA deletion mutant of E. festucae and scored 10 weeks postinoculation, were not consistently significantly different from WT-infected plants in leaf length and tiller number (Figs 7, S8).…”

“…Interestingly, the corresponding TepA homologues in F. graminearum and U. maydis have been shown to be required for virulence on wheat and maize, respectively (Vijayakrishnapillai et al, 2018;Zhang et al, 2010). These species differences might be the result of slightly different infection processes, such as a requirement for chemotaxis.…”

“…In Fusarium graminearum, mutants lacking Fgtep1 displayed reduced conidiation, decreased germination in the presence of wortmannin, and reduced virulence on wheat coleoptiles (Zhang et al, 2010). Similarly, in the corn pathogen Ustilago maydis, deletion of Umptn1 caused a decrease in teliospore production, germination and virulence (Vijayakrishnapillai et al, 2018).…”

Involvement of the Mitochondrial Protein Tyrosine Phosphatase PTPM1 in the Promotion of Conidiation, Development, and Pathogenicity in Colletotrichum graminicola

“…For example, Heymont et al (2000) showed that the phosphatase gene ScTEP1 reduces the ability of S. cerevisiae to sporulate by affecting its process of meiosis, which is accompanied by a decrease in the accumulation of dityrosine, a major component of the yeast cell wall. In addition, the deletion of the related PTPs genes FgTEP1 in F. graminearum or UmPtn1 in U. maydis also affect the formation of spores in these pathogenic fungi ( Zhang et al, 2010 ; Vijayakrishnapillai et al, 2018 ). Although we still do not know the specific reasons for the decrease in conidial production caused by the deletion of CgPTPM1 , based on the results of previous studies, we hypothesized that this gene may be involved in some signaling pathways that result in the reduction of conidiation.…”