Present address: School of Biological Sciences, Washington State University, Pullman, WA 99164–4236, USA
Seed-specific overexpression of a potato sucrose transporter increases sucrose uptake and growth rates of developing pea cotyledons
Article first published online: 7 MAY 2002
The Plant Journal
Volume 30, Issue 2, pages 165–175, April 2002
How to Cite
Rosche, E., Blackmore, D., Tegeder, M., Richardson, T., Schroeder, H., Higgins, T. J. V., Frommer, W. B., Offler, C. E. and Patrick, J. W. (2002), Seed-specific overexpression of a potato sucrose transporter increases sucrose uptake and growth rates of developing pea cotyledons. The Plant Journal, 30: 165–175. doi: 10.1046/j.1365-313X.2002.01282.x
- Issue published online: 7 MAY 2002
- Article first published online: 7 MAY 2002
- Received 22 August 2001; revised 11 January 2002; accepted 22 January 2002.
- Sucrose transporters;
- seed growth;
During the storage phase, cotyledons of developing pea seeds are nourished by nutrients released to the seed apoplasm by their maternal seed coats. Sucrose is transported into pea cotyledons by sucrose/H+ symport mediated by PsSUT1 and possibly other sucrose symporters. PsSUT1 is principally localised to plasma membranes of cotyledon epidermal and subepidermal transfer cells abutting the seed coat. We tested the hypothesis that endogenous sucrose/H+ symporter(s) regulate sucrose import into developing pea cotyledons. This was done by supplementing their transport activity with a potato sucrose symporter (StSUT1), selectively expressed in cotyledon storage parenchyma cells under control of a vicilin promoter. In segregating transgenic lines, enhanced [14C]sucrose influx into cotyledons above wild-type levels was found to be dependent on StSUT1 expression. The transgene significantly increased (approximately 2-fold) transport activity of cotyledon storage parenchyma tissues where it was selectively expressed. In contrast, sucrose influx into whole cotyledons through the endogenous epidermal transfer cell pathway was increased by only 23% in cotyledons expressing the transgene. A similar response was found for rates of biomass gain by intact cotyledons and by excised cotyledons cultured on a sucrose medium. These observations demonstrate that transport activities of sucrose symporters influence cotyledon growth rates. The attenuated effect of StSUT1 overexpression on sucrose and dry matter fluxes by whole cotyledons is consistent with a large proportion of sucrose being taken up at the cotyledonary surface. This indicates that the cellular location of sucrose transporter activity plays a key role in determining rates of sucrose import into cotyledons.