Transcriptomic analyses giving insights into molecular regulation mechanisms involved in cold tolerance by Epichloë endophyte in seed germination of Achnatherum inebrians

Abstract

Plants have developed mutualistic symbiosis with diverse fungal endophytes that increase their fitness by conferring abiotic and biotic stress tolerance. However, the molecular regulation mechanisms involved in stress tolerance remain largely unknown. Drunken horsegrass (Achnatherum inebrians), an important perennial bunchgrass in China, forms a naturally occurring symbiosis with an asexual symbiotic fungus Epichloe gansuensis. The effect of temperature on germination was determined for E. gansuensis-infected (E+) versus non-infected (E−) A. inebrians. Our results indicate that E+ seed have a higher germination rate under low temperature (10 °C) conditions compared with E− seed. To gain insight into the molecular mechanisms involved in the low temperature resistance of E+ drunken horsegrass, Solexa deep-sequencing was used to identify candidate genes showing differential expression. In total, 152 differentially expressed tags were identified, representing 112 up-regulated and 40 down-regulated genes, which were classified into eight functional categories. Many genes were found to be associated with low temperature response, such as genes participating in biosynthesis of alkaloids and unsaturated fatty acids. This study provides the first comprehensive examination of gene expression changes induced by fungal endophyte infection response to low temperature which is essential for understanding the molecular basis of this aspect of endophyte-enhanced plant improvement.