Abstract
Cysteine-rich receptor-like kinases (CRKs) are a large subfamily of plant receptor-like kinases that play a critical role in disease resistance in plants. However, knowledge about the CRK gene family in cotton and its function against Verticillium wilt (VW), a destructive disease caused by Verticillium dahliae that significantly reduces cotton yields is lacking. In this study, we identified a total of 30 typical CRKs in a Gossypium barbadense genome (GbCRKs). Eleven of these (>30%) are located on the A06 and D06 chromosomes, and 18 consisted of 9 paralogous pairs encoded in the A and D subgenomes. Phylogenetic analysis showed that the GbCRKs could be classified into four broad groups, the expansion of which has probably been driven by tandem duplication. Gene expression profiling of the GbCRKs in resistant and susceptible cotton cultivars revealed that a phylogenetic cluster of nine of the GbCRK genes were up-regulated in response to V. dahliae infection. Virus-induced gene silencing of each of these nine GbCRKs independently revealed that the silencing of GbCRK18 was sufficient to compromise VW resistance in G. barbadense. GbCRK18 expression could be induced by V. dahliae infection or jasmonic acid, and displayed plasma membrane localization. Therefore, our expression analyses indicated that the CRK gene family is differentially regulated in response to Verticillium infection, while gene silencing experiments revealed that GbCRK18 in particular confers VW resistance in G. barbadense.
Highlights
Plants are often infected by various pathogens including bacteria, fungi, oomycetes, and nematodes, but unlike animals, plants lack adaptive/acquired immune system, and rely entirely on innate immunity to resist numerous potential pathogens in the environment (Jones and Dangl, 2006; Boller and Felix, 2009; Zhou et al, 2017)
Manual selection resulted in the identification of 63 candidate Cysteine-rich receptor-like kinases (CRKs) family members (Supplementary Table S2), and all of them were further subjected to domain analysis using SMART and InterproScan, which defined a set of typical CRK proteins that included a signal peptide, two stress-antifung domains, one transmembrane domain (TM), and one Pkinase domain (Figure 1A)
GZ 57 in response to V. dahliae (Figure 4). These results suggested that the cotton CRK genes can be activated by V. dahliae, and that a subset of genes contributes to Verticillium wilt (VW) resistance in G. barbadense
Summary
Plants are often infected by various pathogens including bacteria, fungi, oomycetes, and nematodes, but unlike animals, plants lack adaptive/acquired immune system, and rely entirely on innate immunity to resist numerous potential pathogens in the environment (Jones and Dangl, 2006; Boller and Felix, 2009; Zhou et al, 2017). A diverse array of plasma membranebound receptors are employed by plants to perceive endogenous and exogenous signals for regulation of immunity, and these cell surface receptors include receptor-like kinases (RLKs) and receptor-like proteins (RLPs) that harbor different extracellular domains for perception of distinct ligands (He et al, 2018). RLKs are divided into different families according to their extracellular ligand binding domain, such as leucine-rich repeats (LRRs), lectin, lysine motif (LysM), and wall-associated kinases (WAK) (Tör et al, 2009). The N-terminal extracellular region (the ectodomain) of the RLKs extends into the apoplast where it perceives the signals from the pathogen, whereas the C-terminal kinase domain resides within the cytoplasm and relays the perceived signals into the intracellular environment (Kimura et al, 2017)
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