MADS-Box Genes Are Associated with the Petaloidy/Sepaloidy of Stamens in Cytoplasmic Male Sterile Brassica

MADS-box genes are well known for the ABC model of flower development. In this study, we investigated the expressions of A, B and C functions Brassica rapa MADS-box genes in different Ogura cytoplasmic male sterile (CMS) lines of B. juncea, B. oleracea, and their wild types. We observed two AP1-like (BjAP1 and BoCAL1), three PISTILLATA-like (PI-like; BjPI1, BoPI1, and BoPI2) and six AGAMOUS-like (AG-like; BjAGL1, BjAGL2, BjAGL3, BjAGL4, BoAGL1, and BoAGL2) genes to be altered their expressions in the CMS B. juncea and B. oleracea compared to their wild types. Partial and complete petaloidy in the third whorl (stamen) were observed of two CMS B. juncea lines J26 and J27, respectively. Besides, a sepaloidy structure was evident in the third whorl of CMS B. oleracea line 25053. Altered expressions of BjAP1 and BjPI1 in the fourth whorl (pistil) can be correlated with curved and robust stature of pistils in CMS B. juncea. Furthermore, an in silico protein interaction analysis revealed that AP-like, PI-like, and AG-like proteins are in close association with different MADS-box proteins and LEAFY (LFY), UNUSUAL FLORAL ORGANS (UFO), SEUSS (SEU), LEUNIG (LUG) for different floral organ development. We suggest that expressions of MADS-box genes might be dependent on mitochondrial signaling for cytoplasmic homeosis in CMS B. juncea and B. oleracea. The expression dataset on A, B, and C functions MADS-box genes of CMS and wild type B. juncea and B. oleracea presented in this study might be useful for the development of CMS in different Brassica species.