Rhaphiolepis bibas Transcriptome or Gene expression

Organic acids and sugars are the primary components determining the quality and flavor of loquat fruit. In this study, to better understand the mechanism of organic acids and sugars accumulation during the development of loquat fruit. The low ratio of sugars/organic acids 'Jie Fang Zhong' (JFZ) and the high ratio of sugars/organic acids 'Bai Li' (BL) loquat fruits were used as materials. Major organic acids, sugars content, enzyme activities and the expression of genes related to organic acids and sugars metabolism were analyzed during the development of loquat fruit. The results indicated that in both two cultivars, sugar content continued to increase, but organic acid content dramatically decreased in the later stages of fruit development, and the difference in organic acid (malate) and sugar (fructose and sucrose) content between two varieties mainly occurs in the late stage of fruit development. Then, RNA-sequencing technology was performed to investigate the candidate genes of organic acids and sugars metabolism. We found that cytosolic NADP-dependent malic enzyme (cyNADP-ME2), aluminum-activated malate transporter (ALMT9), subunit A of vacuolar H+-ATPase (VHA-A), vacuolar H+-PPase (VHP1), NAD-sorbitol dehydrogenase (NAD-SDH), fructokinase (FK), SUSY in sucrose cleavage (SS-C), sucrose phosphate synthase(SPS1), vacuolar acid invertase(vAI), were the most significant DEGs between JFZ and BL in the later stages of fruit development. Expressions of 12 key DEGs were validated by real-time quantitative PCR (RT-qPCR). Our findings would provide a more comprehensive perspective for understanding the molecular mechanism of organic acid and sugar in loquat flesh and help the breeding of loquat with high quality.