Abstract
Development of seed as a sink proceeds from pre-storage phase, in which sugars are mainly used for cell proliferation, to storage phase, in which sugars are converted into seed storage materials. In legume plants, this transition occurs in parallel with the transition from high hexose/sucrose ratio to high sucrose/hexose ratio. Seeds are converted into source organ after seed germination to support the early vegetative growth. In addition to plant hormones, sugar-dependent regulation of gene expression is likely to play important roles in various phases of seed development and germination. We have isolated sugar-signalling mutants of Arabidopsis, and identified factors involved in the expression of sugar-inducible genes. Among them, an AP2-type transcriptional activator, ASML1/WRI1, seems to regulate partition of sucrose-C into oil during seed development, and B3 domain-EAR motif transcriptional repressors, HSI2 and HSL1, prevent seed maturation program after seed germination.
