The LaeA orthologue in Epichloë festucae is required for symbiotic interaction with Lolium perenne

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

“…This suggests that VelA has a stronger regulatory effect when growing in seedlings and mature plants under likely nutrient limited conditions, compared to PDA culture, a nutrient rich condition. This also correlates with our previous report that showed much higher expression of velA under nutrient limited medium (water agar) compared to nutrient rich medium (PDA) [11], which is similar to LaeA [12].…”

“…As we showed before, the highest laeA expression was also at 14 DPI although it was not a gradual increase as was the case with velA [12]. In addition to velA and laeA having the highest expression at 14 DPI, this time point also correlated with when Δ velA and Δ laeA mutant inoculated seedlings began to die [11, 12]. Because of these reasons, 14 DPI was chosen to study the requirement of velA and laeA on the expression profile of E. festucae during infection of perennial ryegrass.…”

“…In this study, a set of comparative transcriptomics analyses of Δ velA mutants versus wild type E. festucae in culture, in infected seedlings and in infected mature plants was performed. In addition, these results were also compared to the transcriptomics analysis of Δ laeA versus wild type E. festucae in seedlings [12, 37] and in culture. We identified a specific set of VelA regulated genes that define possible processes required for this symbiotic interaction.…”

“…Although the molecular mechanisms that regulate the mutualistic interaction between E. festucae and perennial ryegrass is still largely unknown a number of studies have shown the importance of genes required for hyphal anastomosis (soft gene [10]), fungal biology and development ( velA gene [11] and laeA gene [12]), localised production of reactive oxygen species (required to maintain hyphal polarity [13-16]) and iron homeostasis ( sidN gene [17, 18]). Although it is not clear how Epichloë suppresses or avoids plant responses to establish and maintain a compatible interaction, recent studies have suggested that reducing the chitin inducible host defence response, by altering fungal cell wall chitin, is a possible mechanism [19, 20].…”

“…LaeA is a global fungal regulator and a predicted interaction partner of VelA which we recently reported is required for E. festucae metabolism and development and for establishing and maintaining a successful symbiotic interaction with perennial ryegrass [12]. In addition, a comparative transcriptomics analyses during the early stages of interaction of inoculated perennial ryegrass seedlings with the Δ laeA mutant and wild type E. festucae suggested a regulatory role for LaeA on the expression of genes for plant cell wall degradation, fungal cell wall composition, secondary metabolism and small-secreted proteins [12, 37].…”