Abstract
Plant photosynthesis is reliant on the dynamic assembly and stability of the four multisubunit complexes located in the thylakoid membranes, which work in unison to generate ATP and reducing equivalents required for the Calvin cycle reaction occurring in the stroma. The role of a number of stromal factors in the transcriptional, post-transcriptional and post-translational regulation of membrane complex assembly is well documented, but the contribution of lumenal factors to this process is relatively unknown. The thylakoid lumen has recently been found to containnearly 20 distinct immunophilins, the majority of which are FKBP-type immunophilins. We isolated Arabidopsis mutants lacking the AtFKBP20-2 isoform and show that they display a severe and specific defect in the content of the PSI complex, characterized by an alteration in the stoichiometry of core and antenna subunits. Recent evidence for the role of additional lumenal immunophilins in photosynthetic regulation will also be presented.
