Cooperation of LPA3 and LPA2 Is Essential for Photosystem II Assembly in Arabidopsis    

Abstract

Photosystem II (PSII) is a multisubunit membrane protein complex that is assembled in a sequence of steps. However, the molecular mechanisms responsible for the assembly of the individual subunits into functional PSII complexes are still largely unknown. Here, we report the identification of a chloroplast protein, Low PSII Accumulation3 (LPA3), which is required for the assembly of the CP43 subunit in PSII complexes in Arabidopsis (Arabidopsis thaliana). LPA3 interacts with LPA2, a previously identified PSII CP43 assembly factor, and a double mutation of LPA2 and LPA3 is more deleterious for assembly than either single mutation, resulting in a seedling-lethal phenotype. Our results indicate that LPA3 and LPA2 have overlapping functions in assisting CP43 assembly and that cooperation between LPA2 and LPA3 is essential for PSII assembly. In addition, we provide evidence that LPA2 and LPA3 interact with Albino3 (Alb3), which is essential for thylakoid protein biogenesis. Thus, the function of Alb3 in some PSII assembly processes is probably mediated through interactions with LPA2 and LPA3.

Proteomic Analysis of Chloroplast-to-Chromoplast Transition in Tomato Reveals Metabolic Shifts Coupled with Disrupted Thylakoid Biogenesis Machinery and Elevated Energy-Production Components

“…In addition, there is also an abrupt decrease, between the B and R stages, of two low PSII accumulation proteins (LPA1: Solyc09g074880 and LPA3: Solyc06g068480) involved in the assembly of PSII (Peng et al, 2006;Cai et al, 2010). The two proteins have been clearly identified by Peng et al (2006) and Cai et al (2010) but still annotated as unknown gene in The Arabidopsis Information Resource and Solyc databases. Another protein necessary for the assembly of PSII high chlorophyll fluorescence (HCF136, Solyc02g014150; Plücken et al, 2002) decreases continuously.…”

Regulatory factors for the assembly of thylakoid membrane protein complexes

“…Homologues of LPA2 have been identified in other plants, but not in cyanobacteria or Chlamydomonas [20]. LPA3 does not have any transmembrane domains, and highly conserved LPA3 sequences have been found in plants, Chlamydomonas and Ostreococcus [21]. LPA2 may have evolved after the divergence of the land plant lineage or may have been lost in other lineages.…”

“…Both LPA2 and LPA3 interact with Alb3. This interaction with Alb3 suggests that the function of Alb3 in some PSII assembly processes is most probably mediated through interactions with LPA2 and LPA3 [21].…”

“…The higherplant-specific HCF243 chloroplast protein has been implicated in maintaining the stability of the D1 protein and promoting subsequent PSII assembly [62]. LPA2 and LPA3 (low PSII accmulation 2 and 3), two other thylakoid membrane proteins, have overlapping functions in assisting CP43 assembly, and the cooperation between LPA2 and LPA3 is essential for PSII assembly [20,21]. LPA2 encodes an integral membrane protein containing two transmembrane domains.…”

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

“…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). Psb28 was suggested to be important for the synthesis of chlorophylls and/or apoproteins of the inner antenna subunit CP47 (Dobáková et al, 2009).…”