Journal Article

Protein Synthesis by Rice Coleoptiles During Prolonged Anoxia: Implications for Glycolysis, Growth and Energy Utilization

SHAOBAI HUANG, HANK GREENWAY, TIMOTHY D. COLMER and A. HARVEY MILLAR

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 96, issue 4, pages 703-715
Published in print September 2005 | ISSN: 0305-7364
Published online July 2005 | e-ISSN: 1095-8290 | DOI: https://dx.doi.org/10.1093/aob/mci222
Protein Synthesis by Rice Coleoptiles During Prolonged Anoxia: Implications for Glycolysis, Growth and Energy Utilization

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  • Evolutionary Biology
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Background and Aims Anoxia-tolerant plant tissues synthesize a number of proteins during anoxia, in addition to the ‘classical anaerobic proteins’ involved in glycolysis and fermentation. The present study used a model system of rice coleoptile tips to elucidate patterns of protein synthesis in this anoxia-tolerant plant tissue.

Methods Coleoptile tips 7–11 mm long were excised from intact seedlings exposed to anoxia, or excised from hypoxically pre-treated seedlings and then exposed to anoxia for 72 h. Total proteins or 35S-labelled proteins were extracted, separated using two-dimensional isoelectric focusing/SDS–polyacrylamide gel electrophoresis and analysed using mass spectrometry.

Key Results The coleoptile tips excised after intact seedlings had been exposed to anoxia for 72 h had a similar proteome to tips that were first excised and then exposed to anoxia. After 72 h anoxia, Bowman–Birk trypsin inhibitors and a glycine-rich RNA-binding protein decreased in abundance, whereas a nucleoside diphosphate kinase and several proteins with unknown functions were strongly enhanced. Using [35S]methionine as label, proteins synthesized at high levels in anoxia, and also in aeration, included a nucleoside diphosphate kinase, a glycine-rich RNA-binding protein, a putative elicitor-inducible protein and a putative actin-depolymerizing factor. Proteins synthesized predominately in anoxia included a pyruvate orthophosphate dikinase (PPDK), alcohol dehydrogenase 1 and 2, fructose 1,6-bisphosphate aldolase and a protein of unknown function.

Conclusion The induction of PPDK in anoxic rice coleoptiles might, in combination with pyruvate kinase (PK), enable operation of a ‘substrate cycle’ producing PPi from ATP. Production of PPi would (a) direct energy to crucial transport processes across the tonoplast (i.e. the H+-PPiase); (b) be required for sucrose hydrolysis via sucrose synthase; and (c) enable acceleration of glycolysis, via pyrophosphate:fructose 6-phosphate 1-phosphotransferase (PFP) acting in parallel with phosphofructokinase (PFK), thus enhancing ATP production in anoxic rice coleoptiles; ATP production would need to be increased if there was a substantial requirement for PPi.

Keywords: Anoxia; coleoptile; ethanol production; glycolysis; protein synthesis; proteomics; pyruvate orthophosphate dikinase; pyrophosphate; Oryza sativa

Journal Article.  9674 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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