Abstract:

In order to study the molecular mechanism of carotenoid metabolism of ‘Guanximiyou’ pomelo red mutant line, ‘Guanximiyou’ pomelo (GX), its budding first generation ‘Hongroumiyou’ (HR) and budding second generation ‘Sanhongmiyou’ (SH) were used to study the carotenoid metabolism in the pulp of the three varieties at three development stages by the RNA SEQ technology. By bioinformatics analysis, 10 differentially expressed genes were isolated to participate in the biosynthesis of carotenoids, namely, PSY, ZDS, CRTISO1/2, NPQ1, and 9-cis-epoxy carotenoids, the genes of oxygenase (NCED3/5), abscisic aldehyde oxidase (AAO3), ABA 8’-hydroxylase (CYP707A1), carotenoid cleavage dioxygenases gene (CCD4). Co expression analysis revealed that the expression patterns of seven family transcription factors were highly correlated with carotenoid synthesis genes, which were MADS, bZIP, bHLH, MYB, AP2/ERF, NAC and WRKY. The expression patterns of some genes were verified by real-time quantitative PCR (qRT-PCR), and the results were highly consistent with those of RNA-seq. In addition, DEGs enrichment analysis of primary and secondary metabolic pathways in ‘red flesh honey pomelo’ showed that during the accumulation of carotenoids, genes of cell wall, lipid and flavonoid metabolism were abundant. The results showed that the red flesh mutation of GX was caused by the differential expression of carotenoid metabolism related enzyme genes and the regulation of transcription factors; at the same time, the red bud mutation in flesh was accompanied by the mutation related to juice granulation. This may provide a valuable reference for further study on the formation and accumulation of carotenoids and juice granulation, and also provide a way to analyze the mechanism of different color mutation and juice granulation in pomelo fruit.

Key words: Citrus maxima (Burm.) Merr. cv ‘Guanximiyou’, bud mutation, carotenoid, transcriptome, gene, transcription factor