Curd development associated gene (CDAG1) in cauliflower (Brassica oleracea L. var. botrytis) could result in enlarged organ size and increased biomass

•CDAG1 is a novel organ-sized associated gene firstly identified in cauliflower.•CDAG1 ectopic overexpression could result in bigger organ size then increase biomass.•CDAG1 plays its roles in organ size control by regulating both cell number and cell size.•CDAG1 may function in ethylene-mediated signal pathway.•CDAG1 is an ideal gene resource in breeding high-yielded crops.

The curd is a specialized organ and the most important product organ of cauliflower (Brassica oleracea L. var. botrytis). However, the mechanism underlying the regulation of curd formation and development remains largely unknown. In the present study, a novel homologous gene containing the Organ Size Related (OSR) domain, namely, CDAG1 (Curd Development Associated Gene 1) was identified in cauliflower. Quantitative analysis indicated that CDAG1 showed significantly higher transcript levels in young tissues. Functional analysis demonstrated that the ectopic overexpression of CDAG1 in Arabidopsis and cauliflower could significantly promote organ growth and result in larger organ size and increased biomass. Organ enlargement was predominantly due to increased cell number. In addition, 228 genes involved in the CDAG1-mediated regulatory network were discovered by transcriptome analysis. Among these genes, CDAG1 was confirmed to inhibit the transcriptional expression of the endogenous OSR genes, ARGOS and ARL, while a series of ethylene-responsive transcription factors (ERFs) were found to increased expression in 35S:CDAG1 transgenic Arabidopsis plants. This implies that CDAG1 may function in the ethylene-mediated signal pathway. These findings provide new insight into the function of OSR genes, and suggest potential applications of CDAG1 in breeding high-yielding crops.