Genome-wide characterization and expression profiling of B3 superfamily during flower induction stage in pineapple (Ananas comosus L.)

Abstract

The B3 superfamily is a plant-specific family, which involves in growth and development process. By now, the identification of B3 superfamily in pineapple (Ananas comosus) has not reported. In this study, 57 B3 genes were identified and further phylogenetically classified into five subfamilies, all genes contained B3 domain. Chromosomal localization analysis revealed that 54 of 57 AcB3 genes were located on 21 chromosomes.Collinearity analysis indicated that the segmental duplication was the main event in the evolution of B3 gene superfamily and most of them were under purifying selection. Moreover, there were 7 and 39 pairs of orthologous B3s were identified between pineapple and Arabidopsis or rice, respectively, which indicated the closer genetic relationship between pineapple and rice. Most genes had cis-element of abscisic acid, ethylene, MeJA, light, and abiotic stress. qRT-PCR showed that the expression level of most AcB3 genes were up-regulated within 1 d after ethephon treatment and expressed high level in flower bud differentiation period in stem apex. This study provide a comprehensive understanding of AcB3s and a basis for future molecular studies of ethephon induced pineapple flowering.