Proteomic analysis of chloroplasts from chlorophyll-deficient melon mutant

We aimed to understand the molecular-level changes occurring in the photosynthetic metabolic network in mutant chloroplasts. We performed comparative liquid chromatography-mass spectrometry protein profiling of wild-type (WT) and chlorophyll-deficient melon (Cucumis melo L.) mutants. We identified 390 differentially expressed proteins and 81 shared proteins varied significantly in abundance, of which 76 were upregulated and 5 were downregulated. Differentially expressed proteins were involved in the following biological processes: binding, catalytic, structural, transporter, and antioxidant activities. The mutant had 6.08-fold higher expression of glutamate-1-semialdehyde 2,1-aminomutase (GSAM), an enzyme that synthesizes the chlorophyll precursor, 5-aminolevulinic acid, and a 5.02-fold higher expression of pyridoxal biosynthesis protein, a GSAM coenzyme. An RNA recognition motif-containing protein (RRM) decreased in expression by 5.22-fold. This suggests that GSAM and RRM are particularly relevant to chlorophyll deficiency.