Abstract
Verticillium wilt, caused by Verticillium dahliae, is one of the most damaging and widespread soil-borne cotton diseases. The molecular mechanisms underlying the cotton defense against V. dahliae 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 V. dahliae 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 V. dahliae 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 V. dahliae infection. GhGDH2, encoding glutamate dehydrogenase (GDH), was selected for functional characterization. Suppressing the expression level of GhGDH2 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 V. dahliae resistance. Our finding provides new insights on the molecular mechanisms of cotton resistance to V. dahliae infection and candidate genes for breeding V. dahliae resistance cotton cultivars by genetic modification.
Highlights
Cotton (Gossypium hirsutum L.) is an economically important crop of the Malvaceae family, providing a source of renewable natural fiber and oilseeds
We found that the basal transcriptome landscape between highly resistant (HR) and highly susceptible (HS) has a substantial role in their responses to V. dahliae infection and that V. dahliae resistance is affected by the metabolites of the lignin biosynthesis pathway (Xiong et al, 2021)
The expression level of GhGDH2 at 12 to 72 hpi was significantly higher than that at 0 hpi, with an increase of 1.12- to 6.23-fold (Figure 6E), while the expression level of GhGDH3 was significantly upregulated and downregulated at 12 and 48 hpi, respectively (Figure 6F). These results indicated that GhGDH2 and GhGDH3 may play a potential role in cotton defense against V. dahliae, which could be achieved through SAand jasmonic acid (JA)-mediated signal transduction pathways
Summary
Cotton (Gossypium hirsutum L.) is an economically important crop of the Malvaceae family, providing a source of renewable natural fiber and oilseeds. Verticillium dahliae is a soil-borne fungus and cause of vascular disease known as Verticillium wilt, which is one of the most common and serious diseases in cotton-producing regions worldwide (Cai et al, 2009). V. dahliae can infect cotton by penetrating roots during the whole growing season and result in wilting and defoliation of leaves, and even plant death (Shaban et al, 2018). Breeding resistant cultivars are the most effective, economical, safe, and environmentally friendly method for controlling Verticillium wilt. Due to the lack of disease-resistant germplasm resources in G. hirsutum and variation in V. dahliae strains, the breeding progress on Verticillium wilt resistance is slow (Wang et al, 2016). Understanding the molecular mechanism of Verticillium wilt resistance and identifying Verticillium wilt resistance genes are of great significance for improving Verticillium wilt resistance in cotton by genetic engineering
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