Seed Development group
Heads: Dr. Bruno Mueller
The general goal is to understand and influence regulatory networks of differentiation and storage product accumulation in developing crop seeds. Our interest is focussed on genetic and metabolic/ hormonal regulation of these processes. Thereby, special emphasis is laid on maternal-filial interactions within developing seeds. Scientific work is further focussed on sink-source relationships and on cellular disintegration processes during seed development. Aim of our work is to improve yield and quality of crop seeds. Models are the cereals barley and wheat, and the legumes pea and broad bean (V. faba).
Seed development depends on available assimilates and nutrients delivered by the mother plant. Thereby, demands of the growing seed (sink) are communicated to vegetative plant organs (source). Identification and modification of components mediating sink-source communications with the aim to increase grain yield and quality in wheat and barley is one of the goals of our scientific work.
Cellular disintegration of maternal seed tissues and growing of the fertilization products embryo and endosperm determine morphogenesis of the growing seed (Sreenivasulu et al. 2010). Cellular disintegration is tightly correlated to the expression of vacuolar processing enzymes (VPEs), (Radchuk et al. 2011) and small cysteine-rich proteins (Radchuk et al. 2006) which are localized in the maternal tissues nucellus and nucellar projection (NP) of the barley grain and in the seed coat of pea. Laser-microdissection as established for developing grains allowed transcriptome and metabolite analysis of the supplying maternal tissue (NP) but also of the filial endosperm transfer cells (ETCs) responsible for assimilate uptake. Differentiation and function of the two tissues undergo distinct hormonal regulation but are tightly correlated with each other to ensure coordination between assimilate/ nutrient supply and changing demand of the developing grain (Thiel et al. 2008, 2009). 454-transcriptome sequencing of developing ETCs identified signal transduction chains related to ABA and ethylene which might mediate maternal-filial interactions.
Growth and filling of embryo and endosperm are under metabolic control. Reduction of trehalose-6 phosphate (T6P) levels in pea embryos and immuno-modulation of ABA content in the pea embryo (Radchuk et al. 2011) and the endosperm of barley are projects that will answer questions related to basic science. Together with colleagues from the University of Göttingen, embryonic heterosis was analysed in V. faba seeds. Hybrid embryos develop enhanced sink strength which is established during early seed development and probably mediated by auxin effects (Meitzel et al. 2011). In tight cooperation with breeders, yield and protein yield of winter wheat grains was increased by transgenic approaches (Weichert et al. 2010). The results are important for agricultural application. Together with the breeders and in DFG projects, we are analysing transgene effects on agriculturally relevant traits of winter wheat varieties.