Role of glycine betaine in regulating physiological and molecular aspects of plants under abiotic stress

Under natural conditions, plants are often exposed to different abiotic stresses environments. Such exposure is more frequent due to climate change and has implications in assuring global food security. Plant responses to various types of abiotic stresses are complex and are associated with a set of changes at physiological and molecular levels. Among various changes associated with abiotic stress conditions, accumulation of compatible solutes is one of the early changes take place in plant cells. Glycine betaine (GB) is a well-established compatible solute accumulating in plants, which is known to possess a protective role against a variety of abiotic stresses. At present, its biosynthetic pathway is well elucidated in a variety of organisms, viz., plants, animals, and microbes; and information of genes encoding enzymes of its bio-synthesis is now available. Both the exogenous application of GB and the transgenic expression of GB biosynthetic pathway genes increase the tolerance of plants to various abiotic stress. Further, the role of GB application in enhancing the shelf-life of the fruits and vegetables in postharvest conditions is now well established, along with its role in preventing cold injury during cold storage. The present chapter reviews role of GB in enhancing the tolerance of plants toward different types of abiotic stresses. Lot of efforts have been made to overexpress GB biosynthesis-related genes for higher accumulation of GB in transgenic plants exhibiting enhanced tolerance toward various abiotic stress. Some recent researchers have claimed increased yield potentials via accumulation of GB in plants under nonstress conditions also. Keeping this in mind, the present chapter highlights the recent progress made on our understanding of the role of GB in a variety of abiotic stress with an ultimate aim to utilize this information for developing crop plants with enhance tolerance to abiotic stress and higher productivity, for ensuring global food security.