Transcriptome Analysis and RNA Interference Reveal GhGDH2 Regulating Cotton Resistance to Verticillium Wilt by JA and SA Signaling Pathways

Abstract

Verticillium wilt, caused by <i>Verticillium dahliae</i>, is one of the most damaging and widespread soil-borne cotton diseases. The molecular mechanisms underlying the cotton defense against <i>V. dahliae</i> remain largely elusive. Here, we compared the transcriptional differences between Upland cotton cultivars: one highly resistant (HR; Shidalukang 1) and one highly susceptible (HS; Junmian 1). This was done at multiple time points after <i>V. dahliae</i> inoculation, which identified 2010 and 1275 differentially expressed genes (DEGs) in HR and HS, respectively. Plant hormone signal transduction-related genes were enriched in HR, whereas genes related to lignin biosynthesis were enriched in both HR and HS. Weighted gene co-expression network analysis (WGCNA) using the 2868 non-redundant genes differentially expressed between the <i>V. dahliae</i> infected and uninfected samples in HR or HS identified 10 different gene network modules and 22 hub genes with a potential role in regulating cotton defense against <i>V. dahliae</i> infection. <i>GhGDH2</i>, encoding glutamate dehydrogenase (GDH), was selected for functional characterization. Suppressing the expression level of <i>GhGDH2</i> by virus-induced gene silencing (VIGS) in HS led to inhibition of the salicylic acid (SA) biosynthesis/signaling pathways and activation of the jasmonic acid (JA) biosynthesis/signaling pathways, which resulted in an increase of 42.1% JA content and a reduction of 78.9% SA content in cotton roots, and consequently enhanced <i>V. dahliae</i> resistance. Our finding provides new insights on the molecular mechanisms of cotton resistance to <i>V. dahliae</i> infection and candidate genes for breeding <i>V. dahliae</i> resistance cotton cultivars by genetic modification.