Identification of a peroxisomal-targeted aldolase involved in chlorophyll biosynthesis and sugar metabolism in rice

Chlorophyll plays remarkable and critical roles in photosynthetic light-harvesting, energy transduction and plant development. In this study, we identified a rice Chl-deficient mutant, ygdl-1 (yellow green and droopy leaf-1), which showed yellow-green leaves throughout plant development with decreased content of Chls and carotene and an increased Chl a/b ratio. The ygdl-1 mutant also exhibited severe defects in chloroplast development, including disorganized grana stacks. Sequence analysis revealed that the mutant contained a T-DNA insertion within the promoter of a fructose-1,6-bisphosphate aldolase (OsAld-Y), which dramatically reduced the OsAld-Y mRNA level, and its identity was verified by transgenic complementation. Real-time PCR analysis showed that the expression levels of genes associated with chlorophyll biosynthesis and chloroplast development were concurrently altered in the ygdl-1 mutant. The expression of OsAld-Y-GFP fusion protein in tobacco epidermal cells showed that OsAld-Y was localized to the peroxisome. In addition, the analysis of primary carbon metabolites revealed the significantly reduced levels of sucrose and fructose in the mutant leaves, while the glucose content was similar to wild-type plants. Our results suggest that the OsAld-Y participates in Chl accumulation, chloroplast development and plant growth by influencing the photosynthetic rate of leaves and the sugar metabolism of rice.