Genome-wide analysis of heptahelical protein (HHP) gene family and expression of BcHHP1 in response to stresses in Brassica rapa

Abstract

Heptahelical protein (HHP) signalling pathway is involved in cold acclimation responses to low temperature and other stresses. The HHP transcription factor family is the key component regulating this signalling pathway. In this study, five HHP-like genes, BcHHP1, BcHHP2, BcHHP3, BcHHP4, and BcHHP5, were isolated from non-heading Chinese cabbage (Brassica rapa ssp. chinensis cv. Suzhouqing). Multiple sequence alignment and phylogenetic analysis showed that BcHHP proteins are highly homologous to HHP proteins from Arabidopsis thaliana, Glycine max, Oryza sativa, and Zea mays. Some of these HHP proteins might share similar functions in some aspects, which might be further proved by interaction network of BcHHP genes. Furthermore, real-time quantitative PCR showed that BcHHP1 was induced under cold and salt treatments. Besides, BcHHP1 was also accumulated in response to abscisic acid and salicylic acid, indicating that BcHHP1 gene might participate in response to hormone treatments. In addition, a BcHHP1-YFP fusion protein was localized to the nucleus and cytoplasm. These results indicated that five BcHHP genes might play important roles in a functional HHP signalling pathway responding to cold treatment. This work might be useful for future functional analysis of other HHP-like genes.