Molecular genetics of heterosis of the plant`s earliest stage, the embryo, using the large-seeded faba bean as model
Final Report Abstract
Legume seeds provide important food and feed stuff and are the main source of plant-derived proteins. A deeper understanding of the mechanism which mediates seed growth and development is therefore of high agronomic relevance. Hybrid vigour is usually analysed for yield-related traits. Seed development is controlled by the embryos genetic program. The genotype of the embryo can genetically different from that of their mother plant especially when cross-pollination introduces different male gametes. Thus, early embryos can express heterosis. The aim of the present work was to analyse hybrid vigour at an early embryo stage. Two Vicia faba inbred lines and their crosses served as models to analyse physiological and molecular mechanisms of embryo heterosis. Profiles of transcripts, metabolites and seed contents were compared in developing embryos between the means of reciprocally crossed and selfed seeds growing on the same mother plant. The mean weight of mature hybrid seeds is higher, demonstrating mid-parent heterosis. Hybrid embryos show a prolonged early phase of development and delayed onset of storage activity. Accordingly, transcript profiling indicates stimulation of cell proliferation, an effect, which is potentially mediated by activated auxin functions and a framework of growthrelated transcription factors. On the transcript level, activated cell proliferations increased assimilate uptake activity and thereby seed sink strength. This finally might leads to larger hybrid seeds. We conclude that hybrid seeds are characterised by increased growth at early development, which increased storage capacity, leads to higher metabolic fluxes, which partially are met by increased assimilate uptake capacity. The stimulated growth of hybrid seeds shifts metabolite profiles and potentially depletes available pools. Such observed metabolite shifts are probably secondary effects resulting from higher storage capacity of hybrid seeds, a character, which itself is established very early in seed development.
Publications
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(2010). Quantitative genetic analysis of embryo heterosis in faba bean (Vicia faba L.). Theoretical and Applied Genetics, Vol. 120. 2010, Issue 2, pp 261–270.
Dieckmann S, Link W
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(2011). Hybrid embryos of Vicia faba develop enhanced sink strength, which is established during early development. The Plant Journal, Vol. 65. 2011, Issue 4, pp. 517–531.
Meitzel T, Radchuk R, Link W, Weschke W, Weber H
