Abstract
PsbP is an extrinsic 23-kDa protein in the oxygen-evolving complex of PSII and reported to retain ions essential for the water-splitting reaction. In amphidiploids Nicotiana tabacum, PsbP is nuclear-encoded by a multigene family of four members, which could be divided into two groups by the sequence similarity (group-I: 1A and 5B; group-II: 2AF and 3F). All PsbP members are accumulated and group II comprises major component of PsbP in N. tabacum. To clarify the reason why N. tabacum has four PsbP members, group-specific PsbP-silenced plants were generated by RNAi. When compared to control plants, both group-specific PsbP-silenced plants showed marked decrease of PSII activity, while group-II-silenced plants showed more significant decrease of PSII activity. This result indicates that expressions of all PsbP members are required for the maximum PSII activity in N. tabacum. Further functional characterization of two PsbP groups is on-going.
