Genome-wide identification of CmaGH3 family genes, and expression analysis in response to cold and hormonal stresses in Cucurbita maxima

•Fourteen CmaGH3s were identified in the Cucurbita maxima genome.•CmaGH3–7, CmaGH3–10 and CmaGH3–13 play key roles in the evolution of GH3 family genes in C. maxima.•CmaGH3–6 exhibited higher transcription levels than others in different tissues.•CmaGH3s differentially expressed during cold and hormonal stresses.•Some CmaGH3 genes could be used as candidate genes for cold tolerance breeding. Auxin crosstalk with other plant hormones in a series of responses to environmental stresses, is a process that contributes vitally to plant growth and development. Gretchen Hagen 3 (GH3) family genes play an imperative role in the maintenance of hormone homeostasis and rapid response to biotic/abiotic stresses. Nevertheless, knowledge about GH3s in Cucurbita maxima has not been fully determined. In the present study, a total of 14 GH3 genes were identified and characterized, and their expression profiles were evaluated using real-time PCR. Phylogenetic tree and interspecies collinearity analyses facilitated the evolutionary relationships in C. maxima with other species and prediction of CmaGH3 genes function from genetic and genomic perspectives, respectively. After cold stress, the temporal expression of the CmaGH3 genes in two inbred strains (cold-tolerant inbred line: Cma 7, cold-susceptible inbred line: Cma 14) indicated that CmaGH3–4/6/8/10 were as potential candidate genes for cold tolerance breeding. After phytohormone treatments, CmaGH3–10 and CmaGH3–12 were obviously involved in the response of IAA, ABA and GA stresses. These results indicate that CmaGH3–10 gene may not only be involved in the resistance of pumpkin to cold stress, but also closely associated with auxin homeostasis. In addition, CmaGH3–10 contained 16 SNP sites, four of which are nonsynonymous mutation sites. The polymorphism mutations of CmaGH3–10 will be useful for genetic and breeding study in pumpkin.