Comprehensive Survey of the DELLA Transcription Factors in Cucumber and Functional Characterization of CsDELLA1 in Regulation of GA-Mediated Growth and Development

DELLAs are known as negative regulators of gibberellin (GA) signaling pathway and control many aspects of plant development. In recent years, DELLA family genes were widely studied in many plant species, but little was known about the biological functions of DELLA genes in cucumber. In this study, genome-wide identification of the DELLA gene family members was performed (CsDELLA1–4), and their phylogenetic relationship, conserved motif, gene structure, cis-regulatory elements, and expression pattern were systematically analyzed. Amongst them, CsDELLA1 encoded a protein-harbored DGLLA, LERLE, and less-conserved TVHYNP motif in its N-terminal DELLA domain, implying the possible role of CsDELLA1 in GA-regulated growth and development. As anticipated, silenced CsDELLA1 by virus-induced gene silencing resulted in increased plant height and early flowering phenotypes. In contrast, overexpression of CsDELLA1 in Arabidopsis resulted in dwarf, late flowering, and inhibited hypocotyl elongation phenotypes, indicating that overexpression of CsDELLA1 inhibited the GA response in Arabidopsis. The transgenic plants also produced more buds and shorter siliques than the wild-type (WT) plants, and displayed a significantly longer primary root length than that of WT under exogenous GA3 treatment. Collectively, these results indicated that the CsDELLA1 might play important roles in regulation of GA-mediated growth and development.