AUTHOR=Li Shan , Hai Jun , Wang Zie , Deng Jie , Liang Tingting , Su Linlin , Liu Diqiu 

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

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.741463

DOI=10.3389/fpls.2021.741463

ISSN=1664-462X

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