Abstract
BackgroundTranscriptome and proteome analyses on fruit pulp from the blood orange ‘Zaohong’ and the navel orange ‘twenty-first century’ were performed to study Citrus sinensis quality-related molecular changes during consecutive developmental periods, including young fruit, fruit-coloring onset and fruit delayed-harvest for two months, during which fruit remained on the trees.ResultsThe time-course analysis for the fruit developmental periods indicated a complex, dynamic gene expression pattern, with the numbers of differentially expressed genes (DEGs) between the two cultivars being 119, 426 and 904 at the three continuous stages tested during fruit development and ripening. The continuous increase in total soluble solids over the course of fruit development was correlated with up-regulated sucrose phosphate synthase (SPS) transcription levels in both cultivars. Eleven differentially expressed genes between the two cultivars involved in the flavonoid pathway were significantly enriched at the onset of the fruit-coloring stage when anthocyanins were detected in blood orange alone. Among 5185 proteins, 65 up-regulated and 29 down-regulated proteins were co-expressed with their cognate mRNAs with significant transcription and protein expression levels when the fruits from the two cultivars were compared at the fruit delayed-harvest stage. Additionally, important genes participating in the γ-aminobutyric acid (GABA) shunt were activated in blood orange at two significant expression levels in the fruit delayed-harvest stage. Thus, organic acids in fruit continuously decreased during this stage.ConclusionsThis research was the first to provide a more comprehensive understanding of the differentially expressed genes involved in anthocyanin, sucrose and citrate metabolism at the transcriptome and proteome levels in C. sinensis, especially during the fruit delayed-harvest stage.
Highlights
Transcriptome and proteome analyses on fruit pulp from the blood orange ‘Zaohong’ and the navel orange ‘twenty-first century’ were performed to study Citrus sinensis quality-related molecular changes during consecutive developmental periods, including young fruit, fruit-coloring onset and fruit delayed-harvest for two months, during which fruit remained on the trees
The blond orange became fully ripe (TSS/ titratable acid (TA) = 13.97), while the blood orange was close to full maturity (TSS/TA = 9.29)
At 302 days after flowering (DAF), darker purple-colored rind and flesh formed in the blood orange, while the flesh in the blond orange became darker orange in color
Summary
Transcriptome and proteome analyses on fruit pulp from the blood orange ‘Zaohong’ and the navel orange ‘twenty-first century’ were performed to study Citrus sinensis quality-related molecular changes during consecutive developmental periods, including young fruit, fruit-coloring onset and fruit delayed-harvest for two months, during which fruit remained on the trees. Anthocyanins have a higher antioxidant capacity against oxidative stress induced by excess reactive oxygen species, such as superoxide radicals and hydrogen peroxide; the human body might be protected from oxidative injury by consuming fruits rich in anthocyanin. Blood orange juice contains anthocyanins in differing concentrations depending on the variety, environment and cultivation practices. During post-harvest cold storage, dihydroflavonol channeling towards anthocyanin production in blood orange is boosted, providing more leucoanthocyanidins to enzymes downstream in the pathway [6]. The genes that participate in anthocyanin production and regulation were unclear during C. sinensis fruit delayedharvest from on-tree storage
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