A suite of sucrose transporters expressed in coats of developing legume seeds includes novel pH-independent facilitators
Article first published online: 24 JAN 2007
The Plant Journal
Volume 49, Issue 4, pages 750–764, February 2007
How to Cite
Zhou, Y., Qu, H., Dibley, K. E., Offler, C. E. and Patrick, J. W. (2007), A suite of sucrose transporters expressed in coats of developing legume seeds includes novel pH-independent facilitators. The Plant Journal, 49: 750–764. doi: 10.1111/j.1365-313X.2006.03000.x
- Issue published online: 24 JAN 2007
- Article first published online: 24 JAN 2007
- Received 11 July 2006; revised 8 October 2006; accepted 24 October 2006.
- sucrose transporter;
- functional characterization;
- seed coat
A suite of newly discovered sucrose transporter genes, PsSUF1, PsSUF4, PvSUT1 and PvSUF1, were isolated from the coats of developing pea (Pisum sativum L.) and bean (Phaseolus vulgaris L.) seeds. Sequence analysis indicated that deduced proteins encoded by PsSUF1, PvSUT1 and PvSUF1 clustered in a separate sub-group under sucrose transporter Clade I, whereas the deduced protein encoded by PsSUF4 clustered in Clade II. When expressed in yeast, these genes were shown to encode sucrose transporters with apparent Michaelis Menten constant (Km) values ranging from 8.9 to 99.8 mm. PvSUT1 exhibited functional characteristics of a sucrose/H+ symporter. In contrast, PsSUF1, PvSUF1 and PsSUF4 supported the pH- and energy independent transport of sucrose that was shown to be bi-directional. These transport properties, together with that of counter transport, indicated that PsSUF1, PvSUF1 and PsSUF4 function as carriers that support the facilitated diffusion of sucrose. Carrier function was unaffected by diethylpyrocarbonate and by maltose competition, suggesting that the sucrose binding sites of these transporters differed from those of known sucrose/H+ symporters. All sucrose transporters were expressed throughout the plant and, of greatest interest, were co-expressed in cells considered responsible for sucrose efflux from seed coats. The possible roles played by the novel facilitators in sucrose efflux from seed coats are discussed.