Leucine and its keto acid enhance the coordinated expression of genes for branched-chain amino acid catabolism in Arabidopsis under sugar starvation.
Branched-chain alpha-keto acid dehydrogenase (BCKDH), a multienzyme complex, plays a key role in branched-chain amino acid catabolism. However, it remains unclear whether expression of each subunit is coordinately regulated in plants, which should be important for the efficient assembly of subunits into a functional multienzyme complex. We show that the transcripts from the Arabidopsis E1alpha subunit gene accumulated in dark-adapted leaves and in sugar-starved suspension cells. These results are complementary to our previous report that the transcripts for the E1beta and E2 subunit genes accumulated in sugar-starved cells. Expression of the E1alpha gene is likely to be regulated by hexokinase-mediated sugar signaling, indicating that sugar plays a regulatory role in the coordinated expression of BCKDH subunit genes. Furthermore, Leu and its metabolite alpha-ketoisocaproate have synergistic effects on the enhanced expression of BCKDH subunit genes under sugar starvation. We hence suggest that branched-chain amino acids activate their own degradation pathway in sugar-starved cells through co-induction of each subunit gene of BCKDH.
Fujiki
Y
Y
Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Hongo, 113-0033, Tokyo, Japan. yuki.fujiki@zmbp.uni-tuebingen.de
Ito
M
M
Nishida
I
I
Watanabe
A
A
D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D017360:Arabidopsis / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D003624:Darkness; D004237:Diuron / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D017343:Genes, Plant / Q000235:genetics; D006540:Herbicides / Q000494:pharmacology; D007651:Keto Acids / Q000378:metabolism / Q000494:pharmacology*; D007658:Ketone Oxidoreductases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D007930:Leucine / Q000378:metabolism / Q000494:pharmacology*; D009097:Multienzyme Complexes / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010788:Photosynthesis / Q000187:drug effects; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013395:Sucrose / Q000378:metabolism* / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics
D006540:Herbicides; D007651:Keto Acids; D009097:Multienzyme Complexes; D021122:Protein Subunits; D012333:RNA, Messenger; D018749:RNA, Plant; D013395:Sucrose; C013082:alpha-ketoisocaproic acid; D004237:Diuron; D007658:Ketone Oxidoreductases; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D007930:Leucine