Sugar signaling in plant growth and development

Abstract

Sugars are the primary energy sources produced by green plants via the life- sustaining process of photosynthesis. The metabolic role of sugars as energy compounds and essential metabolites in living organisms has long been recognized. However, genetic and molecular (mutational) studies during the last decade have highlighted the role of sugars as signaling molecules in controlling diverse aspects of plant growth and development. The review focuses on specifi c signaling roles of various sugars particularly hexoses (glucose and fructose), sucrose, trehalose, and small glycans. Moreover, the sugar-specifi c regulations of various genes and the diverse signaling cascades involved have been discussed. The role of hexokinase-kinase-dependent and hexokinase-independent signals (like G proteins) in sugar signal transduction pathways has also been documented. The evidences generated from the analyses of sugar- insensitive mutants and hormone-insensitive mutants have also demonstrated a complex interplay of factors regulating the common signaling capabilities of sugar/hormone interactions. Characterization of sugar-signaling mutants in Arabidopsis has unraveled a complex signaling network that links sugar responses to two plant stress hormones, abscisic acid and ethylene, in opposite ways. Similar cross talk between sugar and other plant hormones in their signaling capabilities has been discussed.