Differential expression of the ascorbate oxidase multigene family of Camellia sinensis in response to stress.

Apoplastic ascorbate oxidase (AO) plays a major role in cell growth. Although AO genes have been studied in depth, some articles have mistakenly identified AO homologues as AO genes. Overall, the divergence between AO genes and AO homologues has not been explored. Meanwhile, there is little information concerning AO and the AO homologue with respect to Camellia sinensis. In the present study, one CsAO homologue and three CsAOs were confirmed by RT-PCR amplification, cloning and sequencing. Multicopper oxidase type 1 (PF00394), type 2 (PF07731) or type 3 (PF07732) domains and one transmembrane helix were the key domains for each member of the cupredoxin family. The CsAOs with their counterparts from seven dicotyledonous plants and three monocotyledonous plants were used to build phylogenetic tree and compare the deduced polypeptides. CsAO may be strongly expressed in the stretch expanded tissues, including bud and root. The abiotic stress-induced expression pattern of the CsAO homologue (CsAO2) is similar to those of CsAO1, CsAO3 and CsAO4. A new and very large group of AO homologues, which may function as AO genes, was present in both dicotyledonous and monocotyledonous plants. Our study may help in identifying stress-responsive AO genes of plants. [ABSTRACT FROM AUTHOR]