Differential protein expression of two photosystem II subunits, PsbO and PsbP, in an albino mutant of Bambusa edulis with chloroplast DNA aberration

The chloroplast genome of an albino mutant isolated from tissue culture of the bamboo Bambusa edulis Munro was examined to identify aberrations. A number of the chloroplast genes encoding ATP synthases, photosystem II subunits, NADH dehydrogenase, and ribosomal proteins had been deleted, at least partially, in the albino mutant. Comparison of the two-dimensional electrophoresis profiles of albino and green bamboos revealed three spots of reduced intensity, indicating repression of these proteins in the albino mutants. Mass spectroscopic analysis subsequently revealed that two of these proteins are 33-kDa subunits of the photosystem II oxygen-evolving protein complex (PsbO) and one is a 23-kDa subunit of photosystem II oxygen-evolving protein complex (PsbP). The genes encoding these two proteins were cloned from B. edulis, and were denoted BePsbO (accession no. EF669513) and BePsbP (accession no. EF669512). Reverse transcription polymerase chain reaction and two-dimensional gel analyses of BePsbO and BePsbP in green and albino bamboos grown in the light or dark revealed that the albino mutant, similar to its green counterpart, sensed the light signal, resulting in the induction of BePsbO and BePsbP transcription, but it did not accumulate the protein products. We conclude that the repression of protein-expressing BePsbO and BePsbP is because of a defect in post-transcriptional regulation in the albino mutant.