Transcriptome analysis of foxtail millet inflorescence tissue in response to Sclerospora graminicola infection

Abstract

Floral reversion caused by Sclerospora graminicola infection seriously affects development and grain formation of floral organs in foxtail millet. Herein, we observed morphological changes to infected panicles from stamen and pistil differentiation to flowering stages, and used RNA sequencing and weighted correlation network analysis (WGCNA) to analyse the key genes and pathways involved in interactions between foxtail millet and S. graminicola. All floral organs of infected panicles, including glume, lemma and palea, transformed into leaf-like structures, leading to malformed inflorescence. Transcriptome analysis showed that S. graminicola infection regulated host physiology and hormone metabolism, and differentially expressed genes (DEGs) were mainly enriched in disease resistance responses involving plant hormone metabolism, peroxidase activity and flavonoid biosynthesis pathways. Subsequently, 8 % of identified DEGs were predicted to be transcription factors, including bHLH and WRKY members related to biotic stress. Plant physiological measurements showed that infection and stress caused by S. graminicola led to changes in antioxidant enzymes superoxide dismutase and peroxidase, and defence hormones jasmonic acid, salicylic acid and 1-aminocyclopropane-1-carboxylic acid in foxtail millet. WGCNA identified 17 hub genes in four key modules (black, magenta, green and turquoise) including a MYB domain protein (Si2g07390), an ethylene-responsive transcription factor ERF094 (Si8g10010) and an NAC domain protein (Si5g40460). The results indicate that transcriptional expression, hormones and oxidation-reduction participate in inflorescence reversion in foxtail millet caused by S. graminicola.