Cloning and characterization of two chlorophyll A/B binding protein genes and analysis of their gene family in Camellia sinensis

In this study, two chlorophyll A/B binding protein (CAB) genes (CsCP1 and CsCP2) in tea plant were cloned. The proteins encoded by these genes belong to the external or internal antenna proteins of PS II, respectively. They may be the targets of physiological regulation for tea leaf cell PS II because they all contain multiple functional domains and modifiable sites. The CAB gene family in the tea genome consists of 25 homologous genes. We measured the expression patterns of ten genes in the CsCP1 and CsCP2 subfamily under six different stresses. CsCP1 expression was inhibited in response to 6 kinds of stress; CsCP2 expression was slightly upregulated only after cold stress and ABA treatment. However, the expression levels of CSA016997 and CSA030476 were upregulated significantly in the six stresses. The results suggested that the 10 CAB genes may have different functions in tea leaves. Moreover, changes in the expression of the 10 genes under stress appear to be related to ABA- and MeJA-dependent signalling pathways, and their responses to MeJA treatment is faster than those to ABA. In addition, we introduced our experiences for cloning the genes in the context of complex genomes.