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A new anaplerotic respiratory pathway involving lysine biosynthesis in isocitrate dehydrogenase‐deficient A rabidopsis mutants
Author(s) -
BoexFontvieille Edouard R. A.,
Gauthier Paul P. G.,
Gilard Françoise,
Hodges Michael,
Tcherkez Guillaume G. B.
Publication year - 2013
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.12319
Subject(s) - isocitrate dehydrogenase , biochemistry , biology , metabolic pathway , lysine , glutamine , metabolism , nad+ kinase , glutamate dehydrogenase , dehydrogenase , respiration , respiratory chain , enzyme , amino acid , glutamate receptor , botany , receptor
Summary The cornerstone of carbon ( C ) and nitrogen ( N ) metabolic interactions – respiration – is presently not well understood in plant cells: the source of the key intermediate 2‐oxoglutarate (2 OG ), to which reduced N is combined to yield glutamate and glutamine, remains somewhat unclear . We took advantage of combined mutations of NAD ‐ and NADP ‐dependent isocitrate dehydrogenase activity and investigated the associated metabolic effects in A rabidopsis leaves (the major site of N assimilation in this genus), using metabolomics and 13 C ‐labelling techniques. We show that a substantial reduction in leaf isocitrate dehydrogenase activity did not lead to changes in the respiration efflux rate but respiratory metabolism was reorchestrated: 2 OG production was supplemented by a metabolic bypass involving both lysine synthesis and degradation. Although the recycling of lysine has long been considered important in sustaining respiration, we show here that lysine neosynthesis itself participates in an alternative respiratory pathway. L ys metabolism thus contributes to explaining the metabolic flexibility of plant leaves and the effect (or the lack thereof) of respiratory mutations.