Genome-wide survey indicates diverse physiological roles of the turnip (Brassica rapa var. rapa) calcium-dependent protein kinase genes

Calcium-dependent protein kinases (CDPKs) as crucial sensors of calcium concentration changes play important roles in responding to abiotic and biotic stresses. In this study, 55 BrrCDPK genes, which were phylogenetically clustered into four subfamilies, were identified. Chromosome locations indicated that the CDPK family in turnip expanded by segmental duplication and genome rearrangement. Moreover, gene expression profiles showed that different BrrCDPKs were expressed in specific tissues or stages. Transcript levels of BrrCDPKs indicated that they were involved in abiotic and biotic stresses and that paralogs exhibited functional divergence. Additionally, we identified 15 Rboh genes in turnip; the results of yeast two-hybrid analysis suggested that BrrRbohD1 interacted only with BrrCDPK10 and that BrrRbohD2 interacted with BrrCDPK4/7/9/10/17/22/23. Most of the genes play an important role in pst DC3000 defense by regulating the accumulation of H(2)O(2) and stomatal closure. Our study may provide an important foundation for future functional analysis of BrrCDPKs and reveal further biological roles.