Poster: Seed biology

Abs # 721: Low internal oxygen levels restrict storage activity of crop plant seeds

Presenter:	Rolletschek, Hardy , rollet@ipk-gatersleben.de
Authors	Rolletschek, Hardy  (A)   Wobus, Ulrich  (A)   Borisjuk, Ljudmilla  (A)
Affiliations:	(A): Institut für Pflanzengenetik und Kulturpflanzenforschung (IPK)

The role of low internal oxygen as potential growth and yield limiting factor has become a hot topic in seed research. Here we provide conclusive evidence that developing seeds of crop plants are subject to hypoxia, affecting both metabolic activity and gene expression. Oxygen-sensitive microsensors and bioluminescence-based in situ imaging of ATP were applied to seeds. For the first time temporal and spatial maps of O2 and ATP levels were determined and related to tissue differentiation and storage. Oxygen levels fell <2.5 micromolar (<0.1 % of atmospheric saturation!) within storing regions of seeds. Hypoxic conditions were reflected in fermentative metabolism as was evident on the level of gene expression, enzyme activity and fermentation products. Hypoxic regions within seeds showed low ATP. An increase in the external oxygen supply in vivo leads to characteristic metabolic changes as determined by metabolic profiling (LC-MS/MS). The increase in oxygen supply was accompanied by elevated levels of ATP, energy charge as well as metabolites of gylcolysis and citrate cycle, indicating higher metabolic and respiratory fluxes. This corresponded to tracer experiments (14C-sucrose) showing that fluxes towards storage products were elevated in response to additional oxygen supply. We conclude that under in vivo conditions low internal oxygen levels can restrict both respiration and overall metabolic activity. It argues for a rate-limiting role of oxygen in storage product accumulation and seed yield.