Lilium regale Wilson WRKY2 Regulates Chitinase Gene Expression During the Response to the Root Rot Pathogen Fusarium oxysporum

Abstract

Root rot, mainly caused by Fusarium oxysporum, is the most destructive disease affecting lily (Lilium spp.) production. The WRKY transcription factors (TFs) have important roles during plant immune responses. To clarify the effects of WRKY TFs on plant defense responses to pathogens, a WRKY gene (LrWRKY2) was isolated from Lilium regale Wilson, which is a wild lily species highly resistant to F. oxysporum. The expression of LrWRKY2, which encodes a nuclear protein, is induced by various hormones (methyl jasmonate, ethephon, salicylic acid, and hydrogen peroxide) and by F. oxysporum infection. In this study, LrWRKY2-overexpressing transgenic tobacco plants were more resistant to F. oxysporum than the wild-type plants. Moreover, the expression levels of jasmonic acid biosynthetic pathway-related genes (NtAOC, NtAOS, NtKAT, NtPACX, NtJMT, NtOPR, and NtLOX), pathogenesis-related genes (NtCHI, NtGlu2, and NtPR-1), and antioxidant stress-related superoxide dismutase genes (NtSOD, NtCu-ZnSOD, and MnSOD) were significantly up-regulated in LrWRKY2 transgenic tobacco lines. Additionally, the transient expression of a hairpin RNA targeting LrWRKY2 increased the susceptibility of L. regale scales to F. oxysporum. Furthermore, an F. oxysporum resistance gene (LrCHI2) encoding a chitinase was isolated from L. regale. An electrophoretic mobility shift assay demonstrated that LrWRKY2 can bind to the LrCHI2 promoter containing the W-box element. Yeast one-hybrid assay results suggested that LrWRKY2 can activate LrCHI2 transcription. An examination of transgenic tobacco transformed with LrWRKY2 and the LrCHI2 promoter revealed that LrWRKY2 activates the LrCHI2 promoter. Therefore, in L. regale, LrWRKY2 is an important positive regulator that contributes to plant defense responses to F. oxysporum by modulating LrCHI2 expression.

Panax notoginseng transcription factor WRKY15 modulates resistance to Fusarium solani by up-regulating osmotin-like protein expression and inducing JA/SA signaling pathways

“…In apple, WRKY46 enhances the resistance to B. dothidea by binding to the W-box element in the MdPBS3.1 promoter and up-regulating MdPBS3.1 expression [ 23 ]. In wild lily ( Lilium regale Wilson) infected with F. oxysporum , WRKY1 positively modulates the expression of the resistance gene LrPR10-5 , leading to strong Fusarium-wilt resistance [ 24 ]. In the current study, the expression levels of three disease resistance-related genes ( Ntosmotin , NtGLU1 , and NtCHI ) were up-regulated in the PnWRKY15 -OE tobacco lines.…”

“…The pET32a- PnWRKY15 recombinant vector was constructed using the ClonExpress II One Step Cloning Kit (Vazyme, China) and then inserted into E. coli BL21 (DE3) cells (Tsingke Biotechnology, China). The expression of the recombinant PnWRKY15 protein was induced by adding 2 mM isopropyl-β-D-1-thiogalactoside to the bacterial solution and incubating at 25 °C for 8 h. The protein was denatured and purified as previously described [ 24 ]. The PPnOLP1 sequence was used to design the following probes containing the W-box element: biotin labeled probe, unlabeled competitor probe, and biotin labeled mutant probe (i.e., mutated W-box) (Supplementary Material 1: Table S4 ).…”

Panax notoginseng WRKY Transcription Factor 9 Is a Positive Regulator in Responding to Root Rot Pathogen Fusarium solani

“…The WRKY TFs bind to the W-box sequence in the promoters of their target genes, including disease resistance-related genes, through the WRKY domain, and then activate or repress the expression of the target genes (Li et al, 2021a ). The interactions between WRKY TFs and their target genes have been elucidated in a variety of plant species on the basis of EMSA and Y1H analyses.…”

Genome-wide characterization of the chitinase gene family in wild apple (Malus sieversii) and domesticated apple (Malus domestica) reveals its role in resistance to Valsa mali

“…WRKY transcription factors are among the largest families of transcriptional regulators in plants and bind to the W-box cis -acting element in the promoter of the target gene ( Zhu et al., 2017 ). In Lilium regale , LrWRKY2 can activate expression of LrCHI2 , which encodes a chitinase, through binding to the W-box cis -element in the promoter of LrCHI2 to enhance host resistance to root rot caused by Fusarium oxysporum ( Li et al., 2021 ). The tobacco Class I chitinase gene NtCHN48 has two W-boxes in the promoter region that are recognized by NtWRKY1 and NtWRKY4, respectively ( Yamamoto et al., 2004 ).…”