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Leucine and its keto acid enhance the coordinated expression of genes for branched-chain amino acid catabolism inArabidopsisunder sugar starvation

FEBS Letters
Wiley Blackwell (John Wiley & Sons)
Publication Date
DOI: 10.1016/s0014-5793(01)02536-4
  • Branched-Chain Amino Acid
  • Branched-Chain α-Keto Acid
  • Hexokinase
  • Sugar Starvation
  • Arabidopsis
  • Biology


Abstract Branched-chain α-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 E1α 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 E1β and E2 subunit genes accumulated in sugar-starved cells. Expression of the E1α 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 α-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.

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