DOI: 10.5061/dryad.c866t1g5c
title: Comparative transcriptome analysis reveals key genes potentially related to organic acid and sugar accumulation in loquat

description: Organic acids and sugars are the primary components that determine the
 quality and flavor of loquat fruits. In the present study, major organic
 acids, sugar content, enzyme activities, and the expression of related
 genes were analyzed during fruit development in two loquat cultivars,
 'JieFangZhong' (JFZ) and 'BaiLi' (BL). Our results
 showed that the sugar content increased during fruit development in the
 two cultivars; however, the organic acid content dramatically decreased in
 the later stages of fruit development. The differences in organic acid and
 sugar content between the two cultivars primarily occured in the late
 stage of fruit development and the related enzymes showed dynamic changes
 in activies during development. Phosphoenolpyruvate carboxylase (PEPC) and
 mNAD malic dehydrogenase (mNAD-MDH) showed higher activities in JFZ at 95
 days after flowering (DAF) than in BL. However, NADP-dependent malic
 enzyme (NADP-ME) activity was the lowest at 95 DAF in both JFZ and BL with
 BL showing higher activity compared with JFZ. At 125 DAF, the activity of
 fructokinase (FRK) was significantly higher in JFZ than in BL. The
 activity of sucrose synthase (SUSY) in the sucrose cleavage direction
 (SS-C) was low at early stages of fruit development and increased at 125
 DAF. SS-C activity was higher in JFZ than in BL. vAI and sucrose phosphate
 synthase (SPS) activities were similar in the two both cultivars and
 increased with fruit development. RNA-sequencing was performed to
 determine the candidate genes for organic acid and sugar metabolism. Our
 results showed that the differentially expressed genes (DEGs) with the
 greated fold changes in the later stages of fruit development between the
 two cultivars were phosphoenolpyruvate carboxylase 2 (PEPC2), mNAD-malate
 dehydrogenase (mNAD-MDH), cytosolic NADP-ME (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), sucrose synthase in sucrose cleavage (SS-C),
 sucrose-phosphate synthase 1 (SPS1), neutral invertase (NI), and vacuolar
 acid invertase (vAI). The expression of 12 key DEGs was validated by
 quantitative reverese transcription PCR (RT-qPCR). Our findings will help
 understand the molecular mechanism of organic acid and sugar formation in
 loquat, which will aid in breeding high-quality loquat cultivars.
description: Loquat fruits from
 cultivars 'JieFangZhong' (JFZ) and
 'BaiLi' (BL) grown in
 the orchards of Changtai County, Putian city,
 Fujian Province, China, were used as the test materials in
 this study. Both cultivars are late maturing, and
 have similar flowering patterns. Thirty
 disease-free fruits of uniform size
 from each cultivar were collected at three developmental
 stages (65, 95, and 125 DAF). RNA-sequencing was
 performed to screen for key genes regulating sugar and organic acid
 metabolisms during the development of loquat fruit. Moreover, organic acid
 content, soluble sugar content, and enzyme activity were
 determined