Activation of the promoters of Arabidopsis genes for the branched-chain alpha-keto acid dehydrogenase complex in transgenic tobacco BY-2 cells under sugar starvation.
Sugar starvation exerted by sub-10 mM levels of sucrose on Arabidopsis T87 suspension-cultured cells triggered marked accumulation of the transcripts of genes for E1beta and E2 subunit of the branched-chain alpha-keto acid dehydrogenase complex. Similar levels of sugar starvation increased the luciferase activity in transgenic tobacco BY-2 lines expressing the Arabidopsis E1beta- or E2-promoter-luciferase fusion gene. These results indicate that sugar levels tightly regulate the E1beta and E2 promoter activity in the heterologous plant system. We further showed in the transgenic tobacco BY-2 lines that sugar-starvation-induced activation of the E1beta and E2 promoters was prevented by K-252a, an inhibitor of Ser/Thr protein kinase, and was enhanced by okadaic acid, an inhibitor of protein phosphatases. By contrast, the cauliflower mosaic virus 35S promoter activity in sugar-starved BY-2 cells was not significantly affected by K-252a and only slightly enhanced by okadaic acid. Taken together, we propose that transcriptional activation of genes for the branched-chain alpha-keto acid dehydrogenase complex and its modulation by specific protein kinases/phosphatases are of critical importance in branched-chain amino acid catabolism in plant cells under sugar starvation.
Fujiki
Yuki
Y
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, 113-0033, Japan. yuki.fujiki@zmbp.uni-tuebingen.de
Ito
Masaki
M
Itoh
Takashi
T
Nishida
Ikuo
I
Watanabe
Akira
A
D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D000123:Acetyltransferases / Q000235:genetics; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D002227:Carbazoles / Q000494:pharmacology; D002460:Cell Line; D002478:Cells, Cultured; D008058:Dihydrolipoamide Dehydrogenase / Q000235:genetics; D051047:Dihydrolipoyllysine-Residue Acetyltransferase; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D026121:Indole Alkaloids; D007658:Ketone Oxidoreductases / Q000235:genetics*; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics*; D019319:Okadaic Acid / Q000494:pharmacology; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011768:Pyruvate Dehydrogenase Complex / Q000235:genetics; D013395:Sucrose / Q000494:pharmacology*; D014026:Nicotiana / Q000166:cytology
D002227:Carbazoles; D026121:Indole Alkaloids; D009097:Multienzyme Complexes; D011768:Pyruvate Dehydrogenase Complex; D019319:Okadaic Acid; D013395:Sucrose; C049985:staurosporine aglycone; D008156:Luciferases; D007658:Ketone Oxidoreductases; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D008058:Dihydrolipoamide Dehydrogenase; D000123:Acetyltransferases; D051047:Dihydrolipoyllysine-Residue Acetyltransferase; D011493:Protein Kinase C; D004121:Dimethyl Sulfoxide