Transcriptomic Analyses Reveals Molecular Regulation of Photosynthesis by Epichloe endophyte in Achnatherum inebrians under Blumeria graminis Infection

Photosynthesis is essential for the growth of all green plants, and the presence of an Epichloe endophyte enhances the photosynthesis of Achnatherum inebrians (drunken horse grass, DHG), including when it is under attack by fungal pathogens. However, few studies have examined the mechanism of the increased photosynthetic activity at the molecular level of A. inebrians when it is under pathogen stress. The present study investigated the effects of the presence of the Epichloe endophyte on the net photosynthetic rate, intercellular CO2 concentration, stomatal conductance, and transpiration rate of DHG plants under a Blumeria graminis infection condition, and we compared the transcriptomes using RNA sequencing. The results showed that the photosynthetic rate of Epichloe endophyte-infected (E+) plants was higher under the B. graminis infection condition, and also without this pathogen, when it was compared with Epichloe endophyte-free (E-) plants. The E+ plants uninfected with B. graminis had 15 up-regulated unigenes that are involved in photosynthesis which were compared to the E- plants that were uninfected with this pathogen. This suggests that the presence of an Epichloe endophyte up-regulates the genes that are involved in the process of photosynthesis.