Temporal Regulation and Subcellular Localization of Alkaline/Neutral Invertase of Developing Zea mays Endosperm: Insights into Sugar Signaling and Carbon Allocation in Cereal Grains
Sucrose is the main form of transportable carbohydrate in plants. Sucrose production, transport and breakdown is central to plant growth and development and carbohydrate storage. Sucrose hydrolysis occurs via two enzymatic pathways, sucrose synthase and invertase (INV) and is essential for directing carbon into various metabolic pathways and for sugar signaling. Two different families of INV exist based on their pH optima and subcellular localization, acid INV and alkaline-neutral INV (A/N-INV). A/N-INV have been a lot less studied in comparison to acid INV. In this study, gene expression was used to identify temporal regulation of 10 maize A/N-INV isoforms in developing maize seeds. Localization of INVAN8, a plastidial form of A/N-INV, using isolated plastids and characterization of a recombinant INVAN8 protein were performed to unravel a new function of A/N-INV in carbon metabolism of non-photosynthetic plastids (amyloplast) of developing maize endosperm.