Overexpression of sucrose transporter gene PbSUT2 from Pyrus bretschneideri, enhances sucrose content in Solanum lycopersicum fruit

Abstract

Sucrose transporters (SUTs) belong to the major facilitator superfamily. The function of SUTs has been intensively investigated in some higher plants, whereas that in pear fruit is unknown. In this study, the cloning and functional characterization of a sucrose transporter, PbSUT2, in pear (Pyrus bretschneideri Rehd. cv. 'Yali') fruits are reported. PbSUT2 encoded a protein of 498 amino acid residues, and was localized in the plasma membrane of transformed onion epidermal cells and Arabidopsis protoplasts. Phylogenetic analysis revealed that PbSUT2 belonged to the SUT4 clade. The phenotype of overexpression of PbSUT2 tomato plants included early flowering, higher fruit quantity and lower plant height. Overexpression of PbSUT2 in transgenic tomato plants led to increases in the net photosynthetic rate in leaves and sucrose content in mature fruit compared with wild-type tomato plants, and a decrease in the contents of glucose, fructose and total soluble sugars in mature fruits. These results suggested that PbSUT2 affected sucrose content in sinks and the flowering phase during tomato plant growth and development.

Keywords: Flowering; Pear; Photosynthetic rate; Sucrose transporter; Sugar content; Transgenic tomato.