Identification and expression of the Cucurbita WRKY transcription factors in response to water deficit and salt stress

WRKY transcription factors (TFs) have been reported to play important roles in plant responses to various stress conditions. Although several studies on the genomic organization of the WRKY gene family in various species have been reported, the information related to the genus Cucurbita is scarce, and null in the case of Cucurbita pepo. The present study aimed to examine the response of Cucurbita pepo to water deficit and salt stress. Additionally, WRKY gene family has been identified and characterized in this species. Shoot growth was negatively affected by both adverse situations. Similarly, both salt and water stress conditions reduced transpiration and stomatal conductance in C. pepo plants. However, the quantum efficiency of PSII decreased only in those plants exposed to salt stress. The increase in proline concentration recorded in C. pepo plants subjected to salt or drought stress point out the important role of this amino acid for plant tolerance to both stress conditions. Based on the genome sequence, 95 CmWRKY genes were found and classified into three main groups according to their orthologues in Arabidopsis. Among these, 24 and 14 CmWRKY genes were responsive to water and salt stresses, respectively. Three water stress-responsive genes were up-regulated under the adverse condition. The expression of six CmWRKY genes was induced by NaCl treatment. Therefore, a total of nine up regulated genes related to both stresses were identified, suggesting their putative involvement in the plant response to water deficit and salt stress.