Chapter 16 - Sugar Regulates Plant Growth and Development Under In Vitro Conditions

Abstract

The process of photosynthesis results in the production of carbohydrates (sugars), which are an integral component of plant metabolism. Sugars exert their effect in almost all of the processes in the plant’s life cycle by storing energy and by providing skeletons for organic compounds under all growing conditions including in vitro. Modulations of carbohydrate metabolism have profound effects on plant growth and development, particularly on cell division and expansion under in vitro conditions. Apart from these functions they serve as important signaling molecules and also can act as primary messengers in signal transduction pathway in a plant system both in in vitro and in vivo environments. They tend to have their impact on various regulatory processes. Recent research has revealed the molecular mechanisms governing signaling and sugar sensing in plants under optimal and stressful environments. For instance demonstration of hexokinase (HXK) as a glucose sensor that modulates gene expression and multiple plant hormone-signaling pathways. Analyses of HXK mutants have provided new evidence for distinct signaling and metabolic activities in growth and development under in vitro conditions. Furthermore, genetic analyses have revealed extensive interactions between sugar and plant hormone signaling, and a central role for hexokinase (HXK) as a conserved glucose sensor. Diverse sugar signals activate multiple HXK-dependent and HXK-independent pathways and use different molecular mechanisms to control transcription, translation, protein stability, and enzymatic activity. Important and complex roles for Snf1-related kinases (SnRKs), extracellular sugar sensors, and trehalose metabolism in plant sugar signaling are now also emerging. The present chapter will give an insight into the importance of sugars alone or in coordination of phytohormones in growth and development under in vitro conditions.