Vacuolar protein degradation via autophagy provides substrates to amino acid catabolic pathways as an adaptive response to sugar starvation in arabidopsis thaliana

Takaaki Hirota, Masanori Izumi, Shinya Wada, Amane Makino, Hiroyuki Ishida

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

The vacuolar lytic degradation of proteins releases free amino acids that plants can use instead of sugars for respiratory energy production. Autophagy is a major cellular process leading to the transport of proteins into the vacuole for degradation. Here, we examine the contribution of autophagy to the amino acid metabolism response to sugar starvation in mature leaves of Arabidopsis thaliana. During sugar starvation arising from the exposure of wild-type (WT) plants to darkness, autophagic transport of chloroplast stroma, which contains most of the proteins in a leaf, into the vacuolar lumen was induced within 2 d. During this time, the level of soluble proteins, primarily Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase), decreased and the amount of free amino acid increased. In dark-treated autophagy-defective (atg) mutants, the decrease of soluble proteins was suppressed, which resulted in the compromised release of basic amino acids, branched-chain amino acids (BCAAs) and aromatic amino acids. The impairment of BCAA catabolic pathways in the knockout mutants of the electron transfer flavoprotein (ETF)/ETF:ubiquinone oxidoreductase (etfqo) complex and the electron donor protein isovaleryl-CoA dehydrogenase (ivdh) caused a reduced tolerance to dark treatment similar to that in the atg mutants. The enhanced accumulation of BCAAs in the ivdh and etfqo mutants during the dark treatment was reduced by additional autophagy deficiency. These results indicate that vacuolar protein degradation via autophagy serves as an adaptive response to disrupted photosynthesis by providing substrates to amino acid catabolic pathways, including BCAA catabolism mediated by IVDH and ETFQO.

Original languageEnglish
Pages (from-to)1363-1376
Number of pages14
JournalPlant and Cell Physiology
Volume59
Issue number7
DOIs
Publication statusPublished - 2018 Jul 1

Keywords

  • Amino acid catabolism
  • Arabidopsis
  • Autophagy
  • Chloroplasts
  • Sugar starvation
  • Vacuolar protein degradation

ASJC Scopus subject areas

  • Physiology
  • Plant Science
  • Cell Biology

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