Regulation of AtSUS2 and AtSUS3 by glucose and the transcription factor LEC2 in different tissues and at different stages of Arabidopsis seed development.

Sucrose synthase (SUS) is a key enzyme of carbon metabolism in heterotrophic tissues of plants. The Arabidopsis genome contains six SUS genes. Two members of this family, namely AtSUS2 (At5g49190) and AtSUS3 (At4g02280) are strongly and differentially expressed in Arabidopsis seed.

Mutation of the transcription factor LEAFY COTYLEDON 2 alters the chemical composition of Arabidopsis seeds, decreasing oil and protein content, while maintaining high levels of starch and sucrose in mature seeds.

The transcription factor LEAFY COTYLEDON 2 (LEC2; At1g28300) is preferentially expressed in developing seeds of Arabidopsis. Detailed biochemical analysis of a loss-of-function lec2 mutant was carried out in seeds 6-21 days after flowering (DAF). In comparison to wild type controls, lec2 seeds had 15% less protein and 30% less oil, but accumulated 140% more sucrose and >5-fold more starch.

Arabidopsis sucrose synthase 2 and 3 modulate metabolic homeostasis and direct carbon towards starch synthesis in developing seeds.

Two genes encoding sucrose synthase (SUS), namely SUS2 (At5g49190) and SUS3 (At4g02280), are strongly and differentially expressed in Arabidopsis seed. Detailed biochemical analysis was carried out in developing seeds 9-21 days after flowering (DAF) of wild type and two knockouts. SUS2 and SUS3 are not redundant genes since single knockouts show a phenotype in developing seeds.

Study of AtSUS2 localization in seeds reveals a strong association with plastids.

Sucrose synthase (SUS) is a key enzyme in sucrose metabolism. This enzyme catalyzes the reversible conversion of sucrose and UDP to UDP-glucose and fructose. In the Arabidopsis SUS gene family (six members), SUS2 is strongly and specifically expressed in Arabidopsis seeds during the maturation phase.