Molecular characterization of CDSP 34, a chloroplastic protein induced by water deficit in Solanum tuberosum L. plants, and regulation of CDSP 34 expression by ABA and high illumination.

We previously described the accumulation of a 34 kDa thylakoid protein, named CDSP 34 for chloroplastic drought-induced stress protein, in Solanum tuberosum plants subjected to water deficit. A full-length CDSP 34 cDNA has been isolated and we report here that mature CDSP 34 is highly similar to two chromoplastic proteins, fibrillin from Capsicum annuum and CHRC (for chromoplast protein C) from Cucumis sativus, components of carotenoid-accumulating structures. Northern and Western analyses showed that both CDSP 34 transcript and protein accumulated from early stages of water deficit. In water-stressed tomato plants, similar increases in the CDSP 34-related transcript amount were noticed in wild-type and ABA-deficient flacca mutant, but protein accumulation was observed only in wild-type, suggesting a posttranscriptional role of ABA in CDSP 34 synthesis regulation. Substantial increases in CDSP 34 transcript and protein abundances were also observed in potato plants subjected to high illumination. The CDSP 34 protein is proposed to play a structural role in stabilizing stromal lamellae thylakoids upon osmotic or oxidative stress.