Abstract
Despite identification of WRKY family genes in numerous plant species, a little is known about WRKY genes in watermelon, one of the most economically important fruit crops around the world. Here, we identified a total of 63 putative WRKY genes in watermelon and classified them into three major groups (I-III) and five subgroups (IIa-IIe) in group II. The structure analysis indicated that ClWRKYs with different WRKY domains or motifs may play different roles by regulating respective target genes. The expressions of ClWRKYs in different tissues indicate that they are involved in various tissue growth and development. Furthermore, the diverse responses of ClWRKYs to drought, salt, or cold stress suggest that they positively or negatively affect plant tolerance to various abiotic stresses. In addition, the altered expression patterns of ClWRKYs in response to phytohormones such as, ABA, SA, MeJA, and ETH, imply the occurrence of complex cross-talks between ClWRKYs and plant hormone signals in regulating plant physiological and biological processes. Taken together, our findings provide valuable clues to further explore the function and regulatory mechanisms of ClWRKY genes in watermelon growth, development, and adaption to environmental stresses.
Highlights
Transcription factors (TFs) play an essential role in regulating the transcription of specific target genes by binding to their promoters
A total of 63 putative ClWRKY genes, including 57 full-length WRKY genes and 6 WRKY partial homologs, were identified in watermelon by Hidden Markov Model (HMM) (PF03106) and TBLASTN search methods. All of these ClWRKY genes could be mapped on the chromosomes from chromosome 1 to 11 and were renamed from ClWRKY1 to ClWRKY63 based on their order on the chromosomes (Table 1; S1 Fig)
ClWRKY56 and ClWRKY61 were not detected in leaves under normal condition, but they were induced by abiotic stresses (Fig 7), suggesting the involvement of these genes in stress signaling
Summary
Transcription factors (TFs) play an essential role in regulating the transcription of specific target genes by binding to their promoters. The WRKY gene family is one of the 10 largest transcription factor families in plants [1]. Proteins in this family possess one or two highly conserved WRKY domains which include a conserved WRKYGQK heptapeptide at Nterminus and a distinctive zinc-finger like motif C2H2 or C2HC at C- terminus [2, 3]. The WRKY domain binds to the cis-acting element W box (TTGACC/T). Identification and expression analysis of watermelon WRKY genes. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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