MoLAEA Regulates Secondary Metabolism in Magnaporthe oryzae

Fungi are rich sources of secondary metabolites of pharmaceutical importance, such as antibiotics, antitumor agents, and immunosuppressants, as well as of harmful toxins. Secondary metabolites play important roles in the development and pathogenesis of fungi. LaeA is a global regulator of secondary metabolism and was originally reported in ; however, its role in secondary metabolism in has not yet been reported. Here, we investigated the role of a gene homologous to (loss of expression) of spp. in , named ( ). Studies on overexpression and knockdown strains have suggested that this gene acts as a negative regulator of sporulation and melanin synthesis. However, it is not involved in the growth and pathogenesis of Transcriptomic data indicated that regulated genes involved in secondary metabolism. Interestingly, we observed (for the first time, to our knowledge) that this gene is involved in benzylpenicillin (penicillin G) synthesis in Overexpression of increased penicillin G production, whereas the silenced strain showed a complete absence of penicillin G compared to its presence in the wild type. We also observed that LaeA interacted with VeA, a velvet family protein involved in fungal development and secondary metabolism, in the nucleus. This study showed that though may not make any contribution in rice blast fungal pathogenesis, it regulates secondary metabolism in and thus can be further studied for identifying other new uncharacterized metabolites in this fungus. causes blast disease, the most serious disease of cultivated rice affecting global rice production. The genome of has been shown to have a number of genes involved in secondary metabolism, but most of them are uncharacterized. In fact, compared to studies of other filamentous fungi, hardly any work has been done on secondary metabolism in It is shown here (for the first time, to our knowledge) that penicillin G is being synthesized in and that is involved in this process. This is the first step in understanding the penicillin G biosynthesis pathway in This study also unraveled the details of how LaeA works by forming a nuclear complex with VeA in , thus indicating functional conservation of such a gene across filamentous fungi. All these findings open up avenues for more relevant investigations on the genetic regulation of secondary metabolism in .