Involvement of Lhcb6 and Lhcb5 in Photosynthesis Regulation in Response to Abiotic Stress.

There are a number of highly conserved photosystem II light-harvesting antenna proteins in moss whose functions are unclear. Here, we investigated the involvement of chlorophyll-binding proteins, and , in light-harvesting and photosynthesis regulation in . or knock-out resulted in a disordered thylakoid arrangement, a decrease in the number of grana membranes, and an increase in the number of starch granule. The absence of or did not noticeably alter the electron transport rates. However, the non-photochemical quenching activity in the mutant was dramatically reduced when compared to wild-type or plants under abiotic stress. plants were more sensitive to photo-inhibition, while plants showed little difference compared to the wild-type plants under high-light stress. Moreover, both mutants showed a growth malformation phenotype with reduced chlorophyll content in the gametophyte. These results suggested that or played a unique role in plant development, thylakoid organization, and photoprotection of PSII in , especially when exposed to high light or osmotic environments.