Molecular Characterization and Defoliation-Induced Expression of a Sucrose Transporter LcSUT1 Gene in Sheep Grass (Leymus chinensis)

摘要

Sucrose is a major photosynthetic product in plants' leaves. Long-distance transport of sucrose requires sucrose transporter (SUT) to perform loading and unloading functions. In this study, a sucrose transporter gene LcSUT1 was cloned from sheep grass (Leymus chinensis (Trin.) Tzvel), a perennial grass of Gramineae: Poaceae. Bioinformatics analysis showed that the gene product LcSUT1 consisting of 12 predicted transmembrane domains and 11 loops belongs to the SUT1 clade. Heterologous expression of LcSUT1 in yeast proved that it was a functional sucrose transporter. Tissue-specific expression analysis showed that LcSUT1 was highly expressed in leaf and leaf sheath. The expression level of LcSUT1 was significantly up-regulated in leaf sheath after defoliation, but was not induced by wound signal. Furthermore, the level of LcSUT1 expression increased in callus, a model sink tissue, when grew on N6 medium without sucrose. Taken together, our results revealed a novel mechanism in which the increased expression of LcSUT1 in leaf sheaths after defoliation was caused by sucrose starvation rather than by wound signal.