Journal Article

Mitochondrial Phosphatidylethanolamine Level Modulates Cyt <i>c</i> Oxidase Activity to Maintain Respiration Capacity in <i>Arabidopsis thaliana</i> Rosette Leaves

Masumi Otsuru, Yanbo Yu, Junya Mizoi, Mari Kawamoto-Fujioka, Jinyin Wang, Yuki Fujiki and Ikuo Nishida

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 54, issue 10, pages 1612-1619
Published in print October 2013 | ISSN: 0032-0781
Published online August 2013 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/pcp/pct104
Mitochondrial Phosphatidylethanolamine Level Modulates Cyt c Oxidase Activity to Maintain Respiration Capacity in Arabidopsis thaliana Rosette Leaves

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Phosphatidylethanolamine is the predominant phospholipid of the mitochondrial inner membrane. In Arabidopsis, pect1-4 mutants exhibit reduced cellular phosphatidylethanolamine levels owing to reduced CTP:phosphorylethanolamine cytidylyltransferase (PECT; EC 2.7.7.14) activity. Consequently, pect1-4 mutants may have decreased mitochondrial phosphatidylethanolamine levels, thereby affecting respiration capacity. Wild-type and pect1-4 plants grew similarly under a short-day condition until 5 weeks, when pect1-4 leaves had slightly less Chl. Total respiration was comparable between wild-type and pect1-4 leaves at 3 weeks and then increased 2-fold in the wild-type but only 1.1-fold in pect1-4 leaves. Compared with the wild type, the Cyt oxidase pathway capacity was reduced by 36% in pect1-4 leaves at 5 weeks and by 43% in pect1-4 mitochondria in 5-week-old rosette leaves. Maximal Cyt c oxidase (COX) activity was 20% lower in pect1-4 mitochondria than in wild-type mitochondria at 5 weeks despite comparable COX II protein levels in mitochondria at that time. Furthermore, COX II protein levels doubled in both wild-type and pect1-4 mitochondria between 3 and 5 weeks. Phosphatidylethanolamine levels were similar between mitochondria from these plants at 3 weeks and then increased by 6.4% in wild-type mitochondria and decreased by 6.5% in pect1-4 mitochondria by 5 weeks. Phosphatidylcholine levels compensated for the decreases in phosphatidylethanolamine levels. COX activity was lower in pect1-4 mitochondria at 5 weeks, most probably due to reduced phosphatidylethanolamine levels and/or an altered phosphatidylethanolamine:phosphatidylcholine ratio. Thus, PECT1 regulates mitochondrial phosphatidylethanolamine levels, which are important for maintaining respiration capacity in Arabidopsis leaves during prolonged growth under short-day conditions.

Keywords: Arabidopsis; Cyt oxidase pathway; Mitochondria; Respiration capacity

Journal Article.  4787 words.  Illustrated.

Subjects: Plant Sciences and Forestry ; Biochemistry ; Molecular and Cell Biology

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