Peach is considered an important economical fruit crop worldwide. Flavor is one of the key factors affecting fruit quality, and it largely depends on soluble sugar and organic acid contents. Sweetness, determined by the level of soluble sugars, is one of the main attributes that influence the degree of consumer satisfaction for peaches. In mature peach fruit, sucrose accounts for over 54% of total soluble sugars, which are mainly stored in the vacuole, occupying up to 90% of the total cell volume. However, the mechanisms underlying sugar accumulation in peach fruit remain largely unknown.  

The molecular breeding of fruit crops group led by Prof. HAN Yuepeng from Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden reports a peach PpTST1 gene encoding tonoplast sugar transporter that is located in the quantitative trait loci (QTL) interval on Chr5 controlling fruit sucrose content. Researchers clarify the mechanism of sucrose accumulation through PpTST1 gene-tagged marker development and functional analysis. 

The group developed one derived Cleaved Amplified Polymorphic Sequence (dCAPS) marker based on a nonsynonymous G/T variant in the third exon of PpTST1. Genotyping of peach cultivars with the dCAPS marker revealed a significant difference in fruit sugar content among genotypes.  

In addition, researchers found that the expression profile of PpTST1 exhibited a consistency with the sugar accumulation pattern, and its transient silencing significantly inhibited sugar accumulation in peach fruits. These results demonstrated the role of PpTST1 in the regulation of sugar accumulation in peach fruit.  

These results are helpful for understanding the mechanisms underlying fruit sugar accumulation, and could be useful for genetic improvement of fruit sweetness in peach breeding programs.   

This work was supported by grants from the National Key Research and Development Program, the National Natural Science Foundation of China, and the China Agriculture Research System. Results were published on International Journal of Molecular Sciences entitled “Functional analysis reveals the regulatory role of PpTST1 encoding tonoplast sugar transporter in sugar accumulation of peach fruit”. 

Development and application of gene-tagged molecular marker (Image by PENG Qian) 

Functional analysis of the PpTST1 gene using the virus-induced gene silencing (VIGS) system in peach fruits (Image by PENG Qian)