Psb29, a Conserved 22-kD Protein, Functions in the Biogenesis of Photosystem II Complexes in Synechocystis and Arabidopsis  

Abstract

Photosystem II (PSII), the enzyme responsible for photosynthetic oxygen evolution, is a rapidly turned over membrane protein complex. However, the factors that regulate biogenesis of PSII are poorly defined. Previous proteomic analysis of the PSII preparations from the cyanobacterium Synechocystis sp PCC 6803 detected a novel protein, Psb29 (Sll1414), homologs of which are found in all cyanobacteria and vascular plants with sequenced genomes. Deletion of psb29 in Synechocystis 6803 results in slower growth rates under high light intensities, increased light sensitivity, and lower PSII efficiency, without affecting the PSII core electron transfer activities. A T-DNA insertion line in the PSB29 gene in Arabidopsis thaliana displays a phenotype similar to that of the Synechocystis mutant. This plant mutant grows slowly and exhibits variegated leaves, and its PSII activity is light sensitive. Low temperature fluorescence emission spectroscopy of both cyanobacterial and plant mutants shows an increase in the proportion of uncoupled proximal antennae in PSII as a function of increasing growth light intensities. The similar phenotypes observed in both plant and cyanobacterial mutants demonstrate that the function of Psb29 has been conserved throughout the evolution of oxygenic photosynthetic organisms and suggest a role for the Psb29 protein in the biogenesis of PSII.

The Chloroplastic Protein THF1 Interacts with the Coiled-Coil Domain of the Disease Resistance Protein N′ and Regulates Light-Dependent Cell Death

“…Chloroplasts from green sectors have organized thylakoid membranes, whereas plastids from white sectors lack organized thylakoids and accumulate numerous membrane-bound vesicles (Wang et al, 2004). Importantly, this phenotype is more pronounced under high light and can be fully rescued under low-light conditions (Keren et al, 2005). Thus, it has been proposed that the absence of THF1 renders the thf1 mutant more susceptible to light-induced damages, resulting in a subsequent breakdown of thylakoid membranes (Keren et al, 2005).…”

“…In Arabidopsis, the thf1 mutant is stunted, with variegated leaves harboring a mix of green and white sectors (Wang et al, 2004;Keren et al, 2005). Chloroplasts from green sectors have organized thylakoid membranes, whereas plastids from white sectors lack organized thylakoids and accumulate numerous membrane-bound vesicles (Wang et al, 2004).…”

“…To further characterize the signaling pathway associated with this response, we conducted yeast two-hybrid (Y2H) screens and identified the protein Thylakoid Formation1 (THF1) as an interacting partner for the CC domains of N9, R3a, and L 3 . THF1 is a chloroplastic protein, but it is encoded by a nuclear gene that is conserved in all oxygenic photoautotrophs, from cyanobacteria to flowering plants (Wang et al, 2004;Keren et al, 2005). The THF1 protein was first identified in photosystem II (PSII) preparations of the cyanobacterium Synechocystis sp PCC 6803 (Kashino et al, 2002) and appears to interact with and regulate PSII components Yamatani et al, 2013).…”

Regulatory factors for the assembly of thylakoid membrane protein complexes

“…A Psb28 homologue is also found in the Arabidopsis genome but its role remains elusive. Arabidopsis and Synechocystis psb29 mutants show increased light sensitivity and an increase in the proportion of uncoupled antenna with increasing light intensities [32]. It is supposed that Psb29 is required for proper assembly of PSII supercomplexes or efficient disassembly of photodamaged PSII complexes [30,32].…”

PsbN Is Required for Assembly of the Photosystem II Reaction Center in Nicotiana tabacum

“…CYP38 was proposed to guide the folding of D1 and presumably CP43 into PSII, a prerequisite for proper assembly of the water-splitting apparatus . Psb29 and the immonophilin FKBP20-2 are required for efficient assembly of PSII supercomplexes (Keren et al, 2005;Lima et al, 2006;Fu et al, 2007). LPA2 and LPA3 cooperate with each other and interact with ALB3 in assisting incorporation and stabilization of CP43 (Ossenbühl et al, 2004;Cai et al, 2010).…”