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Microarrays and biochemical tools to investigate organic acid accumulation in melon fruit (Cucumis melo var. ameri) after60 Co-γ irradiation

Zhang, H., Zhang, Z. B., Wang, H. S., He, C. X., Zhang, X.
Journal of horticultural science & biotechnology 2009 v.84 no.5 pp. 499-504
Cucumis melo, biotechnology, cell walls, citrate (si)-synthase, citrates, enzyme activity, fruiting, genes, high performance liquid chromatography, horticulture, irradiation, melons, messenger RNA, microarray technology, mitochondria, plant hormones, protein content, ribosomes, signal transduction
Microarray studies conducted to determine the accumulation of organic acids in the fruit of 60Co-γ-irradiated melon (Cucumis melo var. ameri) resulted in the detection of 475 differentially expressed genes. Among these, 251 were up-regulated and 224 were down-regulated. This finding included an additional 62 up- and 33 down-regulated unknown (“no hit”) genes. Among the genes identified, 47 showed significant False Discovery Rates (FDR) of < 0.01 and substantial (≥ 2-fold) differential expression.The genes identified included those for the mitochondrial precursor of citrate synthase (CS), genes associated with plant defense responses, cell wall modification, plant hormone synthesis and signal transduction, and the structural constituents of ribosomes, as well as transcription and regulatory factors. The compositions and concentrations of organic acids and CS activities during pre- and post-irradiated fruit development were measured using HPLC and a UV-spectrophotometer. Comparative transcription profiling found several genes that could be related to “sourness” in 60Co-γ-irradiated fruit. Our results also suggested that 60Co-γ-irradiation changed mRNA levels for mitochondrial CS, followed by changes in CS protein levels and/or enzyme activities related to changes in citrate concentration.This may be the primary trigger for citrate accumulation in fruit, post-irradiation.