The Roles of Proline in Plant Growth and the Tolerance to Abiotic Stresses

Proline is one of the effectively compatible osmolytes widely distributed in organisms and is thought to play an important role in the adaptation to drought, salt, heat, heavy metal and many other abiotic stresses. The accumulation of intracellular proline may function in preventing plants from being damaged caused by osmotic stress, scavenging oxidative free radicals, acting as the important source of nitrogen, carbon and NADPH. During the past years, increasing advances have been made in improving the stress tolerance of plants using the genetic transformation of genes involved in proline metabolism. In this review, the roles of proline in plant growth and tolerance to abiotic stresses, signaling pathway related to proline accumulation, uptake and transport of proline under a variety of adverse environmental conditions, and the advances in improving plant stress tolerance by overexpressing genes involved in proline metabolism were summarized in detail.