Transcriptome analysis and validation for potential marker genes of mycorrhizal rice plants in response to feeding with fall armyworm, Spodoptera frugiperda

Rice (Oryza sativa) is a major staple crop grown worldwide that suffers damage from chewing insects, including the fall armyworm (FAW, Spodoptera frugiperda). Rice also establishes root associations with arbuscular mycorrhizal fungi (AMF). But, very little is known about the underlying molecular mechanisms of these interactions. A transcriptome analysis of FAW-damaged and undamaged rice plants colonized or not colonized with mycorrhizae was performed to identify candidate marker genes and gene networks involved in plant defense. We hypothesize that root-AMF symbiosis lead to changes in rice gene expression, up-regulating/down-regulating resistance-related genes, thereby increasing performance of S. frugiperda. Leaves were collected at 24 h after larva feeding from rice plants subjected to  four treatments in a greenhouse experiment: mycorrhizae, FAW-damaged (MD) and undamaged plants (MUD), and non-mycorrhizae damaged (NMD) and undamaged plants (NMUD). Preliminary evidence identified 35843 genes that were annotated and expression profiles revealed transcriptome differences between leaves of the four treatments in leaves. Validation of altered expression levels of eighteen unigenes that encode plant defense biosynthetic enzymes and transcription factors using quantitative real-time PCR (qRT-PCR) will be discussed to reveal novel underlying mechanisms during rice-AMF-FAW interactions. This study presents the first transcriptome analysis of O. sativa plants inoculated with AMF and subjected to FAW feeding. Our results will provide insights into the molecular mechanisms of plant resistance in rice.