Background: WRKY proteins are a large family of transcriptional regulators in higher plant. They are involved in many biological processes, such as plant development, metabolism, and responses to biotic and abiotic stresses. Prior to the present study, only one full-length cucumber WRKY protein had been reported. The recent publication of the draft genome sequence of cucumber allowed us to conduct a genome-wide search for cucumber WRKY proteins, and to compare these positively identified proteins with their homologs in model plants, such asArabidopsis.Results: We identified a total of 55 WRKY genes in the cucumber genome. According to structural features of their encoded proteins, the cucumber WRKY (CsWRKY) genes were classified into three groups (group 1-3). Analysis of expression profiles ofCsWRKYgenes indicated that 48 WRKY genes display differential expression either in their transcript abundance or in their expression patterns under normal growth conditions, and 23 WRKY genes were differentially expressed in response to at least one abiotic stresses (cold, drought or salinity). The expression profile of stress-inducibleCsWRKYgenes were correlated with those of their putativeArabidopsis WRKY (AtWRKY)orthologs, except for the group 3 WRKY genes. Interestingly, duplicated group 3AtWRKYgenes appear to have been under positive selection pressure during evolution. In contrast, there was no evidence of recent gene duplication or positive selection pressure amongCsWRKYgroup 3 genes, which may have led to the expressional divergence of group 3 orthologs.Conclusions: Fifty-five WRKY genes were identified in cucumber and the structure of their encoded proteins, their expression, and their evolution were examined. Considering that there has been extensive expansion of group 3 WRKY genes in angiosperms, the occurrence of different evolutionary events could explain the functional divergence of these genes.

N6-methyladenosine (m⁶A) methylation functions as a vital post-transcriptional and epigenetic modification in higher plants regulated by α-ketoglutarate-dependent dioxygenases (ALKBH). However, the role of ALKBH genes in oriental melon (Cucumis melo L.) fruit ripening has not been explored. Therefore, we treated oriental melon with an exogenous m⁶A demethylase inhibitor (mechlorfenamic acid) then analyzed endogenous ethylene production and ripening-related indicators to explore the effects of m⁶A methylation on ripening. Bioinformatics and real-time quantitative PCR analyses were used to determine the impact of ALKBH genes on key ethylene synthesis gene expression. Treatment effectively inhibited endogenous ethylene production, firmness changes, and soluble solid contents, thereby extending fruit ripening. Eight ALKBH gene family members belonging to five major groups were identified in the melon genome. All members were expressed in ripening fruits, with different expression patterns during ripening. CmALKBH6, CmALKBH7, and CmALKBH8 expression was inhibited by an ethylene inhibitor (1-methylcyclopropene). The transient overexpression (OE) of CmALKBH8 in oriental melon led to the increased expression of the ethylene synthesis genes CmACS1, CmACS2, and CmACO1. In summary, the ethylene-regulated gene CmALKBH8 may participate in oriental melon fruit ripening regulation by modulating the methylation levels of ethylene synthesis-related genes. These findings help us better understand how m⁶A methylation regulates melon ripening.

Horticultural Plant Cold Resistance Mechanism under WRKY Transcription Factor and Sugar Interaction