Abstract: Based on a constructed cDNA library of Camellia oleifera, a complete coding sequence(CDS) encoding a transmembrane aquaporin(AQP)(GenBank protein id: ACF39901), which contains 287 amino acids, was separated and cloned from nearly matured seeds of C. oleifera, by overlapping extension PCR technique. This aquaporin may be translated from two AQP genes(GenBank accession No: EU850810, EU850811), which contain the same CDS and 3′-UTR, whereas their 5′-UTRs are different. One of them has two additional small insertion segments compared with the other gene. By homology alignment and characteristic sequence analysis, it is speculated that this aquaporin belongs to plasma membrane intrinsic protein, designated as CoPIP1-1.By homology modeling, its water channel activity is demonstrated to be affected by the (free) covering of channel mouth caused by electrostatic potential interaction between the N terminus and D loop or B loop. This interaction is regulated by the protonization and phosphorylation gating mechanism, protonization repressing the channel activity by coverage of channel mouth, whereas phosphorylation derepressing the coverage. The results of homology modeling and intracellular oxidative stage of the C. oleifera seeds suggest that the water transport activity of CoPIP1-1 may be constitutively lower, which may be the reason for the seed desiccation during ripening.

Key words: Camellia oleifera, aquaporin, cDNA library, water channel activity, bioinformatics, homology modeling