Expression profiles of respiratory components associated with mitochondrial biogenesis during germination and...

Germination of plant embryo is a dynamic phase-changing process that is driven by a rapid increase in mitochondrial respiration. We studied the development of respiratory electron transport pathways and the profiles of their transcript and protein components during this critical period using wheat embryos. Oxygen consumption through both the cytochrome and alternative pathways increased rapidly upon imbibition. Quantitative RT-PCR analysis using specific primers and western blot analysis using specific antibodies suggested that this respiratory burst was supported both by the stored mRNA and protein components and ones synthesized de novo at least in the cytochrome pathway. Dry embryos also contained transcript and protein of alternative oxidase (AOX), but their levels remained constant during the studied period. By contrast, the alternative pathway capacity showed a marked increase when the cytochrome pathway was inhibited by antimycin A and this increase was associated with increased levels of AOX transcript and protein. Our results suggest that mitochondrial biogenesis is accompanied by sequential and differential gene expression and protein accumulation, and that AOX allows the complex I to continue to conserve energy thus to support embryo germination and initial seedling growth in wheat when the cytochrome pathway is restricted.