Sugar Transporters Controlling Sucrose Accumulation in Bioenergy Grasses

Carbohydrate partitioning is the process whereby photoassimilates are distributed from their site of synthesis in leaves to the rest of the plant. Control of carbohydrate partitioning is crucial for plant growth and development, and underlies all aspects of crop yield, including cellulose deposition in cell walls and sucrose accumulation in storage organs, such as the stems of sugarcane or sweet sorghum. For most plants, fixed carbon, in the form of sucrose, is loaded into the phloem and transported from leaves to non-photosynthetic tissues, such as stems, roots, and fruits. This process is well characterized at the physiological, biochemical, and anatomical levels. Yet despite the obvious importance of carbohydrate partitioning for plant growth and yield, we still know very little about how it is regulated at the molecular level. The best characterized genes that directly function to load sucrose into the phloem are sucrose transporters (SUTs). Recently, several other families of sugar transporters called SWEETs and tonoplast sugar transporters (TSTs) have also been shown to contribute to sucrose partitioning. The long-term goal of the Braun lab is to determine which genes regulate how and where carbon is allocated in plants. In this talk, I will describe our recent findings related to sugar transporters controlling sucrose accumulation and distribution in bioenergy grasses.