Abstract
Verticillium wilt is a soil-borne disease that can cause devastating losses in cotton production. Because there is no effective chemical means to combat the disease, the only effective way to control Verticillium wilt is through genetic improvement. Therefore, the identification of additional disease-resistance genes will benefit efforts toward the genetic improvement of cotton resistance to Verticillium wilt. Based on screening of a BAC library with a partial Ve homologous fragment and expression analysis, a V. dahliae-induced gene, Gbvdr6, was isolated and cloned from the Verticillium wilt-resistant cotton G. barbadense cultivar Hai7124. The gene was located in the gene cluster containing Gbve1 and Gbvdr5 and adjacent to the Verticillium wilt-resistance QTL hotspot. Gbvdr6 was induced by Verticillium dahliae Kleb and by the plant hormones salicylic acid (SA), methyl jasmonate (MeJA) and ethephon (ETH) but not by abscisic acid (ABA). Gbvdr6 was localized to the plasma membrane. Overexpression of Gbvdr6 in Arabidopsis and cotton enhanced resistance to V. dahliae. Moreover, the JA/ET signaling pathway-related genes PR3, PDF 1.2, ERF1 and the SA-related genes PR1 and PR2 were constitutively expressed in transgenic plants. Gbvdr6-overexpressing Arabidopsis was less sensitive than the wild-type plant to MeJA. Furthermore, the accumulation of reactive oxygen species and callose was triggered at early time points after V. dahliae infection. These results suggest that Gbvdr6 confers resistance to V. dahliae through regulation of the JA/ET and SA signaling pathways.
Highlights
Gossypium hirsutum is the most widely cultivated cotton species in the world and is generally susceptible to Verticillium wilt, which is one of the most destructive diseases caused by the soil-borne fungus Verticillium dahliae Kleb (Zhou et al, 2013; Zhang J. et al, 2014)
A BLASTX search of the non-redundant protein sequences database of NCBI revealed that the Gbvdr6 cDNA shared the highest identity (93%) with a receptor-like protein in G. raimondii and with a series of receptor-like proteins associated with Verticillium wilt disease resistance in G. barbadense, Medicago truncatula, Humulus lupulus, Glycine max, Solanum torvum, and Solanum lycopersicoides
Sequence analysis of Gbvdr6 cDNA and DNA revealed no introns within this gene, similar to the reported Verticillium wilt-resistance genes Ve1 in tomato and GbVe, GbVe1, and Gbvdr5 in G. barbadense (Kawchuk et al, 2001; Zhang et al, 2011; Zhang B. et al, 2012; Yang et al, 2015a)
Summary
Gossypium hirsutum ( known as upland or Mexican cotton) is the most widely cultivated cotton species in the world and is generally susceptible to Verticillium wilt, which is one of the most destructive diseases caused by the soil-borne fungus Verticillium dahliae Kleb (Zhou et al, 2013; Zhang J. et al, 2014). In addition to conventional breeding, the genetic engineering of diseaseresistance genes is an effective means of controlling Verticillium wilt in cotton (Wang et al, 2004; Rajasekaran et al, 2005; Tohidfar et al, 2005; Miao et al, 2010; Parkhi et al, 2010; Tian et al, 2010). The identification of additional disease-resistance genes will benefit efforts in the genetic improvement of cotton’s resistance to Verticillium wilt
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