Unravelling Sugar Accumulation in Sugarcane (Saccharum spp.) Stalk: Recent Approaches

Abstract

Sucrose accumulation in developing sugarcane (Saccharum officinarum) is accompanied by a continuous synthesis and cleavage of sucrose in the storage tissues. It is synthesized in source mature leaves and such assimilates stored in the form of sucrose in the stalks of sugarcane that provide 70% of world sugar. During the phloem transportation, sucrose is unloaded into the sink for metabolism and storage. Its accumulation in sugarcane stalks is affected by sucrose supply, metabolism and sink strength. Sucrose accumulation and carbohydrate metabolism in plant species depend upon activity of Sucrose Synthase (SuSy) enzyme. Fast growing tissues in sugarcane such as root apices, immature stem internodes, cells and tissue cultures usually have low sucrose and higher concentration of SAI (soluble acid invertase) which hydrolyses sucrose into glucose and fructose. The sugar yield needs its enhancement to meet the growing demand for sugar. The photosynthesis activity in source leaves decides the amount of sucrose to sink organs. Sucrose metabolism enzymes control sucrose content in sugarcane stalks. Sucrose accumulation is a complex physiological process controlled by network genes. Recent biochemical and molecular approaches have resolved the various developmental and molecular regulation mechanisms for sucrose accumulation in sugarcane. In this review, discussion have been focussed on molecular involved in sucrose metabolism, source-sink communication and storage, microarray analysis, expressed sequence tags (ESTs) studies, physiological and tissue-specific gene regulation that will help further researches to elucidate the regulatory networks of sucrose accumulation to breed high sugar content in sugarcane.