Abstract
Verticillium wilt caused by Verticillium dahliae is a destructive cotton disease causing severe yield and quality losses worldwide. WRKY transcription factors play important roles in plant defense against pathogen infection. However, little has been reported on the functions of WRKYs in cotton's resistance to V. dahliae. Here, we identified 5, 5, and 10 WRKY70 genes in Gossypium arboreum, Gossypium raimondii, and Gossypium hirsutum, respectively, and investigated the expression profiles of all GhWRKY70 genes in various cotton tissues and in response to hormone treatment or V. dahliae infection. Reverse transcription-quantitative PCR analysis showed that GhWRKY70D13 was expressed higher in roots and stems than in other tissues, and up-regulated after V. dahliae inoculation. Knock-down of GhWRKY70D13 improved resistance to V. dahliae in both resistant and susceptible cotton cultivars. Comparative analysis of transcriptomes generated from wild-type and stable RNAi (RNA interference) plant with down-regulated GhWRKY70D13 showed that genes involved in ethylene (ET) and jasmonic acid (JA) biosynthesis and signaling were significantly upregulated in the GhWRKY70D13 RNAi plants. Consistently, the contents of 1-aminocyclopropane-1-carboxylic (ACC), JA, and JA-isoleucine levels were significantly higher in the GhWRKY70D13 RNAi plants than in wild-type. Following V. dahliae infection, the levels of ACC and JA decreased in the GhWRKY70D13 RNAi plants but still significantly higher (for ACC) than that in wild-type or at the same level (for JA) as in non-infected wild-type plants. Collectively, our results suggested that GhWRKY70D13 negatively regulates cotton's resistance to V. dahliae mainly through its effect on ET and JA biosynthesis and signaling pathways.
Highlights
Cotton (Gossypium hirsutum) produces important natural fibers and is one of the most important industrial crops globally
Using the virus-induced gene silencing (VIGS) and RNA interference (RNAi) approaches, we demonstrated that silencing the expression of GhWRKY70D13 enhanced cotton's resistance to V. dahliae, which was likely achieved through upregulating the jasmonic acid (JA) and/or ET biosynthesis and signaling pathways, a potential mechanism different from that of GhWRKY70A05a
Using AtWRKY70 as a query, we identified 5, 5, and 10 WRKY70 transcription factors in G. raimondii (Wang et al, 2012), G. arboreum (Li et al, 2014b), and G. hirsutum (Zhang et al, 2015b; Wang et al, 2019), respectively, indicating no gene loss occurred after polyploidization
Summary
Cotton (Gossypium hirsutum) produces important natural fibers and is one of the most important industrial crops globally. The soil-borne fungus Verticillium dahliae is one of the most destructive pathogens in cotton production areas worldwide (Cai et al, 2009; Wang et al, 2016; Gong et al, 2017). No germplasms of G. hirsutum cultivars have shown immune to Verticillium wilt (Yang et al, 2015). Numerous V. dahliaeresistance genes have been characterized in cotton, including GbWRKY1 (Li et al, 2014a), GhCYP94C1 (Sun et al, 2014), GhERF6 (Yang et al, 2015), GhHDTF1 (Gao et al, 2016), GhERF1-like (Guo et al, 2016), GhbHLH171 (He et al, 2018), and GhJAZ2 (He et al, 2018), only a defoliating strain of V. dahliae was used in most of these studies. There is still limited knowledge of the genetic and molecular mechanisms on the interaction between cotton and V. dahliae
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