Molecular characterization and expression pattern of sorbitol transporter gene PbSOT2 in pear(Pyrus bretschneideri Rehd.) fruit

Abstract

Sorbitol is a primary photosynthetic product and the principal photosynthetic transport substance in plants of the Rosaceae. Sorbitol transporters in the major facilitator superfamily (MFS) are important for phloem loading and sorbitol uptake into sink tissues. Here we report the cloning, localization, and expression analysis of a sorbitol transporter in fruit of Pyrus bretschneideri Rehd. cv. “Yali.” This clone, named PbSOT2, encoded a 537-aa protein with a calculated molecular mass of 57.92 kDa. The predicted protein had 12 transmembrane domains and belonged to the MFS carriers. PbSOT2 was sub-cellularly targeted to the plasma membrane. The expression of PbSOT2 was highest during the rapid enlargement phase of fruit (100 days after full bloom). In addition, the sorbitol content in fruit fluctuated within certain limits, but its proportion of total sugars decreased continuously. This work shows that PbSOT2 may play a role in fruit enlargement and the accumulation of hexose during fruit development.