LOW PHOTOSYNTHETIC EFFICIENCY 1 is required for light-regulated photosystem II biogenesis in Arabidopsis

Abstract

SignificancePhotosystem II (PSII) reaction center protein D1 is encoded by chloroplast gene psbA and is crucial to the biogenesis and functional maintenance of PSII. D1 proteins are highly dynamic under varying light conditions and thus require efficient synthesis, but the mechanism remains poorly understood. We reported that Arabidopsis LPE1 directly binds to the 5′ UTR of psbA mRNA in a light-dependent manner through a redox-based mechanism and facilitates the association of HCF173 with psbA mRNA to regulate D1 translation. These findings fill a major gap in our understanding of the mechanism of light-regulated D1 synthesis in higher plants and imply that higher plants and primitive photosynthetic organisms share conserved mechanisms but use distinct regulators to regulate biogenesis of PSII subunits.

The Arabidopsis pentatricopeptide repeat protein LPE1 and its maize ortholog are required for translation of the chloroplast psbJ RNA

“…We then used Ribo‐seq to analyze chloroplast gene expression in the lpe1‐3 allele described previously (Jin et al ., ). Because the lpe1‐3 plants varied in size, we were able to select mutant and Col‐0 plants at a similar developmental stage (Figure S4a).…”

“…It was reported that recombinant LPE1 binds the psbA 5′UTR in vitro (Jin et al ., ). However, the significance of that interaction is called into question by the results above suggesting that LPE1 has no direct impact on psbA expression.…”

“…LPE1 (AT3G46610) and TPJ1 (GRMZM2G056116) consist of 14 PPR motifs preceded by a predicted chloroplast transit peptide (Figure S1). LPE1 has been shown to localize to chloroplasts (Jin et al ., ) and TPJ1 was detected in the chloroplast nucleoid proteome (Majeran et al ., ). To analyze TPJ1 function in maize, we analyzed the phenotypes of two Mu transposon insertion alleles.…”

“…Our data call into question the functions proposed previously for LPE1 (Jin et al ., ). The PSII deficiency in the lpe1‐3 mutant had been attributed to a defect in psbA translation, but the much stronger reduction in psbJ and psbN expression shown here accounts for their PSII deficiency.…”

“…It seems likely that TPJ1 and LPE1 exert their effect on psbJ translation by binding its 5′UTR. Although an association between LPE1 and the psbJ RNA was not detected by RNA co‐immunoprecipitation (Jin et al ., ), false negatives are common in experiments of that type. Furthermore, the tagged LPE1 used for that experiment was not shown to be functional.…”