Early Stages of Seed Development in Medicago truncatula: Lessons from Genomic Studies

Seed quality and quantity are the two most economically important traits of legumes. As source of proteins, oils, and carbohydrates, legume seeds have received attention from researchers. Like other dicots, the embryo of M. truncatula develops from a globular stage, transitions through heart and torpedo stage, and finally turns into bent cotyledons. Availability of genome sequence, and other community resources like gene expression atlas, mutant collection, and HapMap collection has streamlined gene function discoveries for seed biologists. Early embryo patterning is regulated by WUS/WOX, Leucine Zippers, and Homeobox genes. LEAFY COTYLEDONs (LECs), FUS3 (FUSCA 3), and ABIs (ABSCISIC ACID INSENSITIVE) are the main groups of genes which take over during seed filling. Seed filling is followed by acquisition of desiccation tolerance and longevity. Though this chapter limits itself within the discussion on early seed development, a considerable portion of the final seed size and quality traits is already determined in these stages.