Comparative analysis of GRAS genes in six Cucurbitaceae species provides novel insights into their evolution and function

Background: GRAS proteins are important transcription factors that play essential roles in diverse fundamental processes of plant growth and development. However, the features, evolution and potential functions of GRAS genes among the Cucurbit crops remain largely unknown. Results In this study, we identified 237 GRAS gene sequences from six Cucurbitaceae species. The genomes of Cucumis sativus L., Cucumis melo L., Benincasa hispida L., Citrullus lanatus L. and Lagenaria siceraria L. contain 35 to 37 GRAS genes, whereas 55 are present in Cucurbita moschata L. which should be derived from a recent whole genome duplication. These GRAS genes were divided into sixteen subfamilies on the basis of their phylogenetic relationships. In the SCLB and RAD1 subclade, three specific motifs were found in Cucurbitaceae species, implying the potential Cucurbitaceae-specific functions. Duplication and synteny analysis revealed that segmental and tandem duplication may be the main reasons for the expansion of the GRAS family in Cucurbitaceae species, and that whole-genome duplication is the main reason for the greater number of GRAS genes in Cucurbita moschata L.. Some GRAS genes exhibit tissue-specific, subfamily-specific or Cucurbitaceae-specific expression patterns, implying that they may play key roles in specific developmental processes in cucurbit crops. Conclusions This study provides insights into the features, evolution and potential functions of GRAS genes in Cucurbitaceae species, which may be associated with important agronomic traits.