Knockdown of the <i><scp>A</scp>rabidopsis thaliana</i> chloroplast protein disulfide isomerase 6 results in reduced levels of photoinhibition and increased <scp>D</scp>1 synthesis in high light

Abstract

Summary A chloroplast protein disulfide isomerase ( PDI ) was previously proposed to regulate translation of the unicellular green alga C hlamydomonas reinhardtii chloroplast psb A m RNA , encoding the D 1 protein, in response to light. Here we show that A t PDI 6, one of 13 A rabidopsis thaliana PDI genes, also plays a role in the chloroplast. We found that A t PDI 6 is targeted and localized to the chloroplast. Interestingly, A t PDI 6 knockdown plants displayed higher resistance to photoinhibition than wild‐type plants when exposed to a tenfold increase in light intensity. The A t PDI 6 knockdown plants also displayed a higher rate of D 1 synthesis under a similar light intensity. The increased resistance to photoinhibition may not be rationalized by changes in antenna or non‐photochemical quenching. Thus, the increased D 1 synthesis rate, which may result in a larger proportion of active D 1 under light stress, may led to the decrease in photoinhibition. These results suggest that, although the D 1 synthesis rates observed in wild‐type plants under high light intensities are elevated, repair can potentially occur faster. The findings implicate A t PDI 6 as an attenuator of D 1 synthesis, modulating photoinhibition in a light‐regulated manner.