The molecular basis of storage organs in Brassicas

The LEAFY COTYLEDON (LEC) family of genes are intrinsically linked to the formation of the Arabidopsis embryo in morphogenesis and maturation. They play several roles in this process including maintenance of embryonic identity and the formation of storage products in the seed. This is important for desiccation protection and as an energy store for germination and growth before photomorphogenesis occurs. Loss of function mutations have been shown to exhibit non-embryonic traits such as trichomes and anthocyanin sequestration. When LECs are expressed outside of embryonic tissues in Arabidopsis, accumulation of storage oils and immature cell identity is observed. They appear to exhibit large amounts of crosstalk with the hormones auxin and gibberellins. This thesis investigates the link between Leafy Cotyledon 1 (LEC1) expression in the Arabidopsis turnip (tnp), a gain-of-function mutant of LEC1, and hypocotyl development in selected Brassica sp. In particular; Are LECs ectopically expressed in the hypocotyl of the Brassicas post germination? To what extent are LEC1, LEC2 and FUSCA3 (FUS3) expressed in relation to one another? Is the timing of starch and lipid accumulation linked temporally to LEC expression? Fatty acid profiles of the tnp mutant were explored in relation to the wild type and further investigations and comparisons to profiles in the Brassica hypocotyl tissues were examined. Relatively high ectopic LEC expression was observed in the Brassica hypocotyl tissue. LEC1 was found to be associated with hypocotyl expansion and starch accumulation. LEC2 expression levels increase after LEC1 levels decrease. The same oils observed to increase in the tnp mutant of Arabidopsis are present in large amounts in the Brassica hypocotyl tissue, suggesting a potential link between LECs and the molecular basis of storage organ development in Brassicas