Allelic variation in PtoPsbW associated with photosynthesis, growth, and wood properties in Populus tomentosa.

Photosynthesis is one of the most important reactions on earth. PsbW, a nuclear-encoded subunit of photosystem II (PSII), stabilizes PSII structure and plays an important role in photosynthesis. Here, we used candidate gene-based linkage disequilibrium (LD) mapping to detect significant associations between allelic variations of PtoPsbW and traits related to photosynthesis, growth, and wood properties in Populus tomentosa. PtoPsbW showed the highest expression in leaves and it increased during the development of these leaves, suggesting that PtoPsbW may play an important role in plant growth and development. Analysis of nucleotide diversity and LD revealed that PtoPsbW has low single-nucleotide polymorphism (SNP) diversity (π tot = 0.0048 and θ w = 0.0050) and relatively low average value of LD (0.1500), indicating that PtoPsbW is conserved due to its indispensable function. Using single-SNP associations in an association population of 435 individuals, we identified five significant associations at the threshold of P ≤ 0.05, explaining 3.28-15.98 % of the phenotypic variation. Haplotype-based association analyses indicated that 13 haplotypes (P ≤ 0.05) from six blocks were associated with photosynthesis, growth, and wood properties. Our work shows that identifying allelic variation and LD can help to decipher the genetic basis of photosynthesis and could potentially be applied for molecular marker-assisted selection in Populus.

Dark-adapted spinach thylakoid protein heterogeneity offers insights into the photosystem II repair cycle.

In higher plants, thylakoid membrane protein complexes show lateral heterogeneity in their distribution: photosystem (PS) II complexes are mostly located in grana stacks, whereas PSI and adenosine triphosphate (ATP) synthase are mostly found in the stroma-exposed thylakoids. However, recent research has revealed strong dynamics in distribution of photosystems and their light harvesting antenna along the thylakoid membrane. Here, the dark-adapted spinach (Spinacia oleracea L.) thylakoid network was mechanically fragmented and the composition of distinct PSII-related proteins in various thylakoid subdomains was analyzed in order to get more insights into the composition and localization of various PSII subcomplexes and auxiliary proteins during the PSII repair cycle. Most of the PSII subunits followed rather equal distribution with roughly 70% of the proteins located collectively in the grana thylakoids and grana margins; however, the low molecular mass subunits PsbW and PsbX as well as the PsbS proteins were found to be more exclusively located in grana thylakoids. The auxiliary proteins assisting in repair cycle of PSII were mostly located in stroma-exposed thylakoids, with the exception of THYLAKOID LUMEN PROTEIN OF 18.3 (TLP18.3), which was more evenly distributed between the grana and stroma thylakoids. The TL29 protein was present exclusively in grana thylakoids. Intriguingly, PROTON GRADIENT REGULATION5 (PGR5) was found to be distributed quite evenly between grana and stroma thylakoids, whereas PGR5-LIKE PHOTOSYNTHETIC PHENOTYPE1 (PGRL1) was highly enriched in the stroma thylakoids and practically missing from the grana cores. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy.