Comprehensive identification of sugar transporters in the Actinidia chinensis genomes reveals their potential roles in sugar accumulation of kiwifruits

Abstract

Sugar transmembrane transport is crucial for cellular energy, sugar homeostasis, fruit yield and quality. However, the characterization of sugar transporter (ST) families in significant fleshy fruits is limited. In this study, 22 candidate ST genes were identified and comprehensively analyzed for chromosomal distribution, conserved domains and molecular characteristics. Phylogenetic analysis and evolutionary selection pressures showed high evolutionary conservation of ST families. Gene Ontology (GO) enrichment and cis-regulatory element analyses supported their involvement in developmental regulation and sugar transport. Expression levels of the STs in different tissues and developmental stages of fruit were analyzed, showing significant correlations between the transcript levels of AcSUT5, AcTST1, and AcERD6-1 and soluble sugar accumulation. Virus-induced silencing AcSUT5 and AcTST1 in kiwifruit fruits decreased soluble sugar concentration, while silencing AcERD6-1 increased sugar accumulation, suggesting AcSUT5 and AcTST1 act as importers facilitating sugar influx into vacuole, whereas AcERD6-1 functions as an exporter mediating vacuole sugar efflux. Transcription factor prediction identified key regulatory proteins. This study provides insights into sugar transport in kiwifruit and a basis for molecular breeding targeting enhanced fruit quality.

Keywords: Actinidia chinensis; Expression profile; Soluble sugar; Sugar transporter.