VelA and LaeA are key regulators of theEpichloë festucaetranscriptomic response during symbiosis with perennial ryegrass

Abstract

VelA (or VeA) is a key global regulator in fungal secondary metabolism and development which we previously showed is required during the symbiotic interaction of Epichloë festucae with perennial ryegrass. In this study, comparative transcriptomics analyses of ΔvelA mutant compared to wild type E. festucae, under three different conditions (in culture, infected seedlings and infected mature plants) were performed to investigate the impact VelA on the E. festucae transcriptome. These comparative transcriptomics studies showed that VelA regulates the expression of genes encoding proteins involved in membrane transport, fungal cell wall biosynthesis, host cell wall degradation and secondary metabolism, along with a number of small secreted proteins and a large number of proteins with no predictable functions. In addition, these results were compared with previous transcriptomics experiments studying the impact of LaeA, another key global regulator of secondary metabolism and development that we have shown is important for the E. festucae- perennial ryegrass interaction. The results showed that although VelA and LaeA regulate a sub-set of E. festucae genes in a similar manner, they also regulated many other genes independently of each other suggesting specialised roles.

Functional roles of LaeA, polyketide synthase, and glucose oxidase in the regulation of ochratoxin A biosynthesis and virulence in Aspergillus carbonarius

“…In the present study, LaeA positively regulated the expression of most of the tested genes encoding cell wall-degrading enzymes in A. carbonarius (Figure 7). These results were in agreement with previous reports on the interaction of an endophytic fungus Epichloë festucae with perennial ryegrass, which suggested a regulatory role for LaeA in the expression of genes for plant cell wall degradation (Rahnama et al, 2019(Rahnama et al, , 2020. We assume that the deletion of AclaeA could affect A. carbonarius pathogenicity through down-regulation of the cell wall-degrading enzymes, including cellulases, hemicellulases, and pectolytic enzymes.…”

“…The influence of the carbon catabolite repressor protein (CreA) on the plant cell wall-degrading enzymes of several Aspergillus species has been extensively studied. In those species, CreA has been reported to act as a negative regulator of genes encoding arabinases, several endoxylanases, and pectinolytic enzymes (Bussink et al, 1991;Kester et al, 1996;Orejas et al, 1999;Ruijter et al, 1997). creA mutant strains of A. nidulans and Aspergillus niger displayed (partially) derepressed phenotypes (Ruijter et al, 1997;Shroff et al, 1997).…”