Physiological and transcriptomic characterization of a yellow-green leaf mutant of maize

Abstract Background Chlorophylls, green pigments in chloroplasts, are essential for photosynthesis. Reduction in chlorophyll contents may result in retarded growth, dwarfism, and sterility. In this study, a yellow-green leaf mutant of maize, indicative of abnormity in chlorophyll contents, was identified. The physiological parameters of this mutant were measured. Next, global gene expression of this mutant was determined using transcriptome analysis and compared to that of wild-type maize plants. Results The yellow-green leaf mutant of maize was found to contain lower contents of chlorophyll a , chlorophyll b and carotenoid compounds. It contained fewer active PSII centers and displayed lower values of original chlorophyll fluorescence parameters than the wild-type plants. The real-time fluorescence yield, the electron transport rate, and the net photosynthetic rate of the mutant plants showed reduction as well. In contrast, the maximum photochemical quantum yield of PSII of the mutant plants was similar to that of the wild-type plants. Comparative transcriptomic analysis of the mutant plants and wild-type plants led to the identification of differentially expressed1122 genes, of which 536 genes were up-regulated and 586 genes down-regulated in the mutant. Five genes in chlorophyll metabolism pathway, nine genes in the tricarboxylic acid cycle and seven genes related to the conversion of sucrose to starch displayed down-regulated expression. In contrast, genes encoding a photosystem II reaction center PsbP family protein and the PGR5-like protein 1A (PGRL1A) exhibited increased transcript abundance. Conclusions The yellow-green leaf mutant of maize contained fewer active PSII centers with lowered net photosynthesis rate, but have the similar value of the maximum photochemical quantum yield of PSII with that of the wild-type plants. Analysis of differentially expressed genes through transcriptome analysis revealed the down-regulated genes which may be responsible for chlorophyll deduction and changes of photosynthetic characteristics. The up-regulated genes would be helpful to maintain the active PSII centers of the yellow-green leaf mutant.