Regulation of sulfur-responsive gene expression by exogenously applied cytokinins in Arabidopsis thaliana.
Effects of plant hormones on a sulfur-deficiency responsive element (betaSR) from the promoter region of the beta subunit gene of beta-conglycinin, a major seed storage protein of soybean, were investigated using transgenic Arabidopsis thaliana. Among the hormones tested, the cytokinins, trans-zeatin (Z) and trans-zeatin riboside, upregulated gene expression directed by the betaSR element both in the presence and in the absence of sulfate in the medium. Z also increased transcript accumulation of two endogenous sulfur-responsive genes, the adenosine 5'-phosphosulfate reductase (APR1) and the Sultr2;2, a sulfate transporter. Concentrations of cytokinins were unaltered during early stages of sulfur starvation when expression of these genes was upregulated. Z did not alter concentrations of O-acetyl-L-serine, a positive regulator of gene expression in sulfur starvation response. Concentrations of sucrose, which is known to upregulate expression of APR1, were increased in rosette leaves by Z. Sucrose application to the medium also increased expression directed by the betaSR element, although sucrose concentrations in tissues were not significantly altered by sulfur availability. These results suggest that exogenously applied cytokinins positively regulate expression of these sulfur responsive genes through a pathway independent of that from sulfur starvation, possibly through increasing sucrose concentrations in tissues.
Ohkama
Naoko
N
Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, 113-8657 Japan. aa07023@mail.ecc.u-tokyo.ac.jp
Takei
Kentaro
K
Sakakibara
Hitoshi
H
Hayashi
Hiroaki
H
Yoneyama
Tadakatsu
T
Fujiwara
Toru
T
D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D027321:Anion Transport Proteins; D052179:Antigens, Plant; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D003583:Cytokinins / Q000494:pharmacology*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D005916:Globulins / Q000235:genetics; D007541:Isopentenyladenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D010088:Oxidoreductases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D050862:Oxidoreductases Acting on Sulfur Group Donors; D030821:Plants, Genetically Modified; D055314:Seed Storage Proteins; D030262:Soybean Proteins / Q000235:genetics; D013395:Sucrose / Q000378:metabolism / Q000494:pharmacology; D013455:Sulfur / Q000172:deficiency* / Q000494:pharmacology; D015026:Zeatin / Q000494:pharmacology
D027321:Anion Transport Proteins; D052179:Antigens, Plant; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D003583:Cytokinins; D005916:Globulins; D055314:Seed Storage Proteins; D030262:Soybean Proteins; C455460:Sultr1;2 protein, Arabidopsis; C013894:beta-conglycinin protein, Glycine max; D013395:Sucrose; D013455:Sulfur; D007541:Isopentenyladenosine; D015026:Zeatin; C009699:zeatin riboside; D010088:Oxidoreductases; D050862:Oxidoreductases Acting on Sulfur Group Donors; C019618:adenylylsulfate reductase; D000241:Adenosine