Cloning of two contrasting high-affinity sulfate transporters from tomato induced by low sulfate and infection by the vascular pathogen Verticillium dahliae.
Two cDNAs, LeST1-1 (AF347613) and LeST1-2 (AF347614), encoding sulfate transporters have been cloned from tomato (Lycopersicon esculentum Mill.) by reverse transcription-polymerase chain reaction and their expression characterised. Sharing 76% identity at the amino acid level, the transporters are phylogenetically associated with the Group-1, high-affinity plant sulfate transporters. Both were shown to have high affinity for sulfate by uptake kinetic analysis using a yeast (Saccharomyces cerevisiae) sulfate-transporter mutant. Km values of 11.5 microM and 9.8 microM were calculated for LeST1-1 and LeST1-2, respectively, the same order of magnitude as those previously reported for several other Group-1 high-affinity sulfate transporters. In situ hybridisation to S-deficient tomato roots showed LeST1-1 to be expressed in the epidermis and pericycle, whereas LeST1-2 expression was located to the epidermis only. Northern analysis shows that the mRNA abundances of both LeST1-1 and LeST1-2 are upregulated in the root in response to sulfate deprivation. LeST1-1 is specifically expressed in root tissue, a characteristic of Group-1 sulfate transporters. LeST1-2, however, was also detected in tomato leaves and stems and is upregulated and expressed to a similar extent in these tissues under conditions of sulfate deprivation. Induction of LeST1-2 expression was also observed in the vascular tissues of a resistant line of tomato infected with the vascular wilt pathogen Verticillium dahliae.
Howarth
Jonathan R
JR
Rothamsted Research, West Common, Harpenden, Hertfordshire, AL5 2JQ, UK.
Fourcroy
Pierre
P
Davidian
Jean-Claude
JC
Smith
Frank W
FW
Hawkesford
Malcolm J
MJ
D001483:Base Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular / Q000379:methods; D017931:DNA Primers; D017403:In Situ Hybridization; D007700:Kinetics; D018551:Solanum lycopersicum / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology*; D026901:Membrane Transport Proteins; D010935:Plant Diseases / Q000382:microbiology; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology; D000076988:Sulfate Transporters; D013431:Sulfates / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics*; D020172:Verticillium / Q000472:pathogenicity*
D002352:Carrier Proteins; D017931:DNA Primers; D026901:Membrane Transport Proteins; C085609:SLC26A4 protein, human; D000076988:Sulfate Transporters; D013431:Sulfates