Molecular cloning and expression analysis of tea plant aquaporin (AQP) gene family

The role of aquaporin proteins (AQPs) has been extensively studied in plants. However, the information of AQPs in the tea plant (Camellia sinensis) is unclear. In this manuscript, we isolated 20 full-length AQP cDNAs from the tea plant, and these sequences were classified into five subfamilies. The genes in these subfamilies displayed differential expression profiles in the studied tissues. The CsAQP expression patterns correlated with flower development and opening (FDO) and bud endodormancy (BED). To better understand the short-term expression patterns of CsAQPs in response to abiotic stress, tea plants were treated with abscisic acid (ABA), cold, salt or drought. ABA treatment down-regulated the expression of various CsAQPs. Salt up-regulated the transcription of most CsAQP genes. Cold treatment resulted in a complicated transcriptional regulation pattern for various CsAQPs. The expression of CsAQPs, especially plasma membrane intrinsic proteins (CsPIPs) and tonoplast intrinsic proteins (CsTIPs), was induced by drought and remained relatively high after rehydration in leaves, whereas almost all the CsAQPs were repressed in roots. Our results highlighted the diversity of CsAQPs in the tea plant and demonstrated that the CsPIP and CsTIP genes play a vital role in the stress response as well as in FDO and BED. Furthermore, certain CsSIPs (small basic intrinsic proteins), CsNIPs (NOD26-like intrinsic proteins) and CsXIPs (X intrinsic proteins) may regulate BED and FDO.