Effects of light intensity on metabolism of light-harvesting pigment and photosynthetic system in Camellia sinensis L. cultivar ‘Huangjinya’

Abstract ‘Huangjinya’ (HJY) is a light-sensitive chlorotic tea cultivar ( Camellia sinensis L. ) that grows chlorotic shoots under sun-light conditions but its chlorotic shoots turn green under weak light conditions. However, the mechanisms responsible for light intensity-induced changes in leaf color remain unclear. In this study, we compared HJY plants with chlorotic leaves exposed to sun-light (Y) and HJY plants with green leaves exposed to both sun and shade (Y + S) on the basis of metabolite profiles, expression of proteins and genes in the pigment metabolic pathway and photosynthetic system. Our results showed that inhibition of chlorophyll synthesis and enhancement of chlorophyll degradation were the reasons for the decrease of chlorophyll content in Y. And the blocked sites were located in the transition stage of chlorophyll synthesis from chloroplast stroma to thylakoid membrane, i.e. from COPPIII to PPIX. In addition, the decrease of photosynthetic system-related proteins and the obstruction of photosynthetic electron transport in Y resulted in the decrease of photosynthetic efficiency. The tolerance of chlorotic leaves to sun-light conditions was enhanced by strengthening xanthophyll cycle and cyclic electron transport. Altogether, this study provides a better understanding of the mechanisms responsible for the chlorotic phenotype.