AUTHOR=Liang Jiayu , Li Xiaodan , Wen Ya , Wu Xinyi , Wang Hui , Li Dayong , Song Fengming 

TITLE=Genome-Wide Characterization of the Methyl CpG Binding Domain-Containing Proteins in Watermelon and Functional Analysis of Their Roles in Disease Resistance Through Ectopic Overexpression in Arabidopsis thaliana

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.886965

DOI=10.3389/fpls.2022.886965

ISSN=1664-462X

ABSTRACT=<p>Methyl-CPG-Binding Domain (MBD) proteins play important roles in plant growth, development, and stress responses. The present study characterized the <italic>MBD</italic> families in watermelon and other cucurbit plants regarding the gene numbers and structures, phylogenetic and syntenic relationships, evolution events, and conserved domain organization of the MBD proteins. The watermelon ClMBD proteins were found to be localized in nucleus, and ClMBD2 and ClMBD3 interacted with ClIDM2 and ClIDM3. ClMBD2 bound to DNA harboring methylated CG sites but not to DNA with methylated CHG and CHH sites <italic>in vitro</italic>. The <italic>ClMBD</italic> genes exhibited distinct expression patterns in watermelon plants after SA and MeJA treatment and after infection by fungal pathogens <italic>Fusarium oxysporum</italic> f.sp. <italic>niveum</italic> and <italic>Didymella bryoniae</italic>. Overexpression of <italic>ClMBD2</italic>, <italic>ClMBD3</italic>, or <italic>ClMBD5</italic> in Arabidopsis resulted in attenuated resistance against <italic>Botrytis cinerea</italic>, accompanied by down-regulated expression of <italic>AtPDF1.2</italic> and increased accumulation of H<sub>2</sub>O<sub>2</sub> upon <italic>B. cinerea</italic> infection. Overexpression of <italic>ClMBD1</italic> and <italic>ClMBD2</italic> led to down-regulated expression of <italic>AtPR1</italic> and decreased resistance while overexpression of <italic>ClMBD5</italic> resulted in up-regulated expression of <italic>AtPR1</italic> and increased resistance against <italic>Pseudomonas syringae</italic> pv. <italic>tomato</italic> DC3000. Transcriptome analysis revealed that overexpression of <italic>ClMBD2</italic> in Arabidopsis up-regulated the expression of a small set of genes that negatively regulate Arabidopsis immunity. These data suggest the importance of some <italic>ClMBD</italic> genes in plant immunity and provide the possibility to improve plant immunity through modification of specific <italic>ClMBD</italic> genes.</p>