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Leucine and its keto acid enhance the coordinated expression of genes for branched‐chain amino acid catabolism in Arabidopsis under sugar starvation
Author(s) -
Fujiki Yuki,
Ito Masaki,
Nishida Ikuo,
Watanabe Akira
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)02536-4
Subject(s) - catabolism , biochemistry , protein subunit , amino acid , biology , gene , arabidopsis , branched chain amino acid , gene expression , hexokinase , sugar , mutant , leucine , enzyme , glycolysis
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.