Transcriptome Profiling Analysis Reveals Co-Regulation of Hormone Pathways in Foxtail Millet during Sclerospora graminicola Infection

Abstract

<i>Sclerospora graminicola</i> (Sacc.) Schroeter is a biotrophic pathogen of foxtail millet (<i>Setaria italica</i>) and increasingly impacts crop production. We explored the main factors for symptoms such as dwarfing of diseased plants and the "hedgehog panicle" by determining panicle characteristics of varieties infected with <i>S.</i> <i>graminicola</i> and analyzing the endogenous hormone-related genes in leaves of Jingu 21. Results indicated that different varieties infected by <i>S. graminicola</i> exhibited various symptoms. Transcriptome analysis revealed that the ent-copalyl diphosphate synthetase (<i>CPS</i>) encoded by Seita.2G144900 and ent-kaurene synthase (<i>KS</i>) encoded by Seita.2G144400 were up-regulated 4.7-fold and 2.8-fold, respectively. Results showed that the biosynthesis of gibberellin might be increased, but the gibberellin signal transduction pathway might be blocked. The abscisic acid (ABA) 8'-hydroxylase encoded by Seita.6G181300 was continuously up-regulated by 4.2-fold, 2.7-fold, 14.3-fold, and 12.9-fold from TG1 to TG4 stage, respectively. Seita.2G144900 and Seita.2G144400 increased 79-fold and 51-fold, respectively, at the panicle development stage, promoting the formation of a "hedgehog panicle". Jasmonic acid-related synthesis enzymes <i>LOX2s</i>, <i>AOS</i>, and <i>AOC</i> were up-regulated at the early stage of infection, indicating that jasmonic acid played an essential role in early response to <i>S. graminicola</i> infection. The expression of <i>YUC</i>-related genes of the auxin synthesis was lower than that of the control at TG3 and TG4 stages, but the amidase encoded by Seita.2G313400 was up-regulated by more than 30-fold, indicating that the main biosynthesis pathway of auxin had changed. The results suggest that there was co-regulation of the hormone pathways during the infection of foxtail millet by <i>S. graminicola</i>.