Functional Characterization of the Arabidopsis AtSUC2 Sucrose/H+ Symporter by Tissue-Specific Complementation Reveals an Essential Role in Phloem Loading But Not in Long-Distance Transport


This article discusses functional characterization of the Arabidopsis AtSUC2 Sucrose/H+ Symporter.

Creation Date: September 2008
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Creator (Author):
Srivastava, Avinash C.

University of North Texas

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Ganesan, Savita

University of North Texas

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Ismail, Ihab O.

University of North Texas

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Ayre, Brian G.

University of North Texas

Publisher Info:
Place of Publication: [Rockville, Maryland]
  • Creation: September 2008

This article discusses functional characterization of the Arabidopsis AtSUC2 Sucrose/H+ Symporter.

Department: Biological Sciences

Plant Physiology, September 2008, Vol. 148, pp. 200-211,; © American Society of Plant Biologists


Abstract: AtSUC2 (At1g22710) encodes a phloem-localized sucrose (Suc)/H+ symporter necessary for efficient Suc transport from source tissues to sink tissues in Arabidopsis (Arabidopsis thaliana). AtSUC2, however, is also expressed strongly in the transport phloem, where its role is more ambiguous, and it has been implicated in mediating both efflux and retrieval to and from flanking tissues via the apoplast. To characterize the role of AtSUC2 in controlling carbon partitioning along the phloem path, AtSUC2 cDNA was expressed from tissue-specific promoters in an Atsuc2 mutant background. Suc transport in this mutant is highly compromised, as indicated by stunted growth and the accumulation of large quantities of sugar and starch in vegetative tissues. Expression of AtSUC2 cDNA from the 2-kb AtSUC2 promoter was sufficient to restore growth and carbon partitioning to nearly wild-type levels. The GALACTINOL SYNTHASE promoter of Cucumis melo (CmGAS1p) confers expression only in the minor veins of mature leaves, not in the transport phloem of larger leaf veins and stems. Mutant plants expressing AtSUC2 cDNA from CmGAS1p had intermediate growth and accumulated sugar and starch, but otherwise they had normal morphology. These characteristics support a role for AtSUC2 in retrieval but not efflux along the transport phloem and show that the only vital function of AtSUC2 in photoassimilate distribution is phloem loading. In addition, AtSUC2 mutant plants, although debilitated, do grow, and AtSUC2-independent modes of phloem transport are discussed, including an entirely symplastic pathway from mesophyll cells to sink tissues.

Physical Description:

12 p.

Keyword(s): phloem | plants | flanking tissues | carbon partitioning
Source: Plant Physiology, 2008, Rockville: American Society of Plant Biologists, pp. 200-211
UNT College of Arts and Sciences
UNT Scholarly Works
  • DOI: 10.1104/pp.108.124776 |
  • ARK: ark:/67531/metadc78290
Resource Type: Article
Format: Text
Access: Public
Publication Title: Plant Physiology
Volume: 148
Page Start: 200
Page End: 211
Peer Reviewed: Yes