Sugars function as essential signaling molecules and metabolic substrates in plant growth, development, yield formation, and fruit quality. The aril of litchi (
Litchi chinensis Sonn.) accumulates high levels of hexoses, primarily glucose and fructose; however, the molecular mechanisms underlying this process remain
[...] Read more.
Sugars function as essential signaling molecules and metabolic substrates in plant growth, development, yield formation, and fruit quality. The aril of litchi (
Litchi chinensis Sonn.) accumulates high levels of hexoses, primarily glucose and fructose; however, the molecular mechanisms underlying this process remain poorly characterized. This study aimed to systematically identify the monosaccharide transporter (
MST) gene family in litchi and elucidate its role in aril sugar accumulation. Through a comprehensive analysis of the litchi genome, we identified a total of 45
LcMST genes, which were classified into seven distinct subfamilies:
STP,
ERD6L,
PLT,
INT,
pGlcT,
TMT, and
VGT. Analysis of gene structure and conserved motifs revealed notable conservation among members within the same subfamily. Collinearity and gene duplication analyses suggested that the
LcMST family expanded through both tandem and whole-genome duplication events, a process primarily governed by purifying selection. Expression profiling across diverse tissues demonstrated that
LcMST genes exhibit distinct tissue-specific expression patterns. During fruit development in the hexose-dominant cultivar ‘Tianshuili’, the expression of the tonoplast monosaccharide transporter gene
LcTMT1 exhibited a significant positive correlation with the accumulation of fructose, glucose, and total sugars. Heterologous functional complementation assays in yeast confirmed the ability of LcTMT1 to transport both glucose and fructose. In conclusion, this study presents the first genome-wide identification and characterization of the
MST gene family in litchi, and identifies
LcTMT1 as a key contributor of hexose accumulation in the aril. These findings establish a foundation for elucidating the molecular mechanisms of sugar accumulation in litchi fruit and for guiding future genetic improvement of fruit quality.
Full article