Comparative transcriptome analysis reveals key genes potentially related to organic acid and sugar accumulation in loquat

PLoS One. 2021 Apr 29;16(4):e0238873. doi: 10.1371/journal.pone.0238873. eCollection 2021.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acids / metabolism
  • Carbohydrate Metabolism
  • Carbohydrates / genetics
  • Eriobotrya / genetics*
  • Eriobotrya / growth & development
  • Eriobotrya / metabolism
  • Fruit / genetics*
  • Fruit / growth & development
  • Fruit / metabolism
  • Gene Expression Profiling
  • Gene Expression Regulation, Plant*
  • Genes, Plant
  • Transcriptome

Substances

  • Acids
  • Carbohydrates

Associated data

  • Dryad/10.5061/dryad.c866t1g5c

Grants and funding

Specific grant numbers: KFA18081A Initials of authors who received each award: Guohua Zheng Full names of commercial companies that funded the study or authors: Screening and analysis of key genes for malate metabolism in loquat fruit Initials of authors who received salary or other funding from commercial companies:No URLs to sponsors’ websites: No Also state whether any sponsors or funders (other than the named authors) played any role in: The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.