Genome-wide identification of YABBY genes and functional characterization of CRABS CLAW (AktCRC) in flower development of Akebia trifoliata.

As a representative species of basal eudicots, Akebia trifoliata has a unique unisexual flower development model, while the internal mechanism of its transition from a bisexual to unisexual flower is still lacking. Here, 6 AktYABs genes were firstly identified from A. trifoliata and divided into five clades: YAB2, FIL/YAB3, INO, CRC, and YAB5. Collinearity analysis and structure analysis proved that AktYABs members were highly conservative. Promoter cis-acting element analysis and RT-qPCR indicated that AktYABs were relative to various development, environmental stress, and hormone response events. All AktYABs members were located in the nucleus and membrane, but only AktYAB2 showed transcriptional activation activity. GUS staining manifested that the AktCRC transcript was strongly accumulated in the leaf, flower meristem, carpel, and tip of mature silique in Arabidopsis. Heterologous expression of AktCRC in Arabidopsis crc-1 mutants could significantly rescue the short siliques phenotype and the defect of apical carpel fusion. The AktCRC regulated carpellary development by affecting the expression levels of auxin synthesis, transport-related genes YUC4, TRN2, and floral meristem homeostasis regulation factor WUS. These results reveal the function of AktCRC in regulating the development of unisexual flowers in A. trifoliata and also lay a foundation for understanding the evolutionary status of the YABBY family in basal eudicots.