The sucrose transporter of celery. Identification and expression during salt stress.
In celery (Apium graveolens L.), long-distance transport of reduced carbon occurs both in the form of sucrose (Suc) and mannitol. The presence of mannitol has been related to the resistance of celery to salt stress. To investigate the transport events occurring during salt stress, we have cloned the H(+)/Suc transporter of celery AgSUT1 (A. graveolens Suc uptake transport 1) from a mature leaf cDNA library. The function of the encoded protein was confirmed by expression in yeast. AgSUT1 is a H(+)/Suc transporter with a high affinity for Suc (K(m) of 139 microM). Another closely related cDNA (AgSUT2) was also identified. AgSUT1 is mainly expressed in mature leaves and phloem of petioles, but also in sink organs such as roots. When celery plants were subjected to salt stress conditions (30 d watering with 300 mM NaCl) favoring mannitol accumulation (J.D. Everard, R. Gucci, S.C. Kann, J.A. Flore, W.H. Loescher [1994] Plant Physiol 106: 281-292), AgSUT1 expression was decreased in all organs, but markedly in roots. The results are discussed in relation to the physiology of celery.
Noiraud
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Laboratoire de Physiologie et Biochimie Végétales, Centre National de la Recherche Scientifique Equipe Supérieure Associée 6161, 40, Avenue du Recteur Pineau, F-86022 Poitiers cedex, France.
Delrot
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S
Lemoine
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D000595:Amino Acid Sequence; D019661:Apiaceae / Q000378:metabolism*; D001483:Base Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride
D002352:Carrier Proteins; D018076:DNA, Complementary; D026901:Membrane Transport Proteins; D010940:Plant Proteins; C078729:sucrose transport protein, plant; D012965:Sodium Chloride