Removal of Feedback Inhibition of Δ1-Pyrroline-5-Carboxylate Synthetase Results in Increased Proline Accumulation and Protection of Plants from Osmotic Stress

Abstract

The ⌬ 1 -pyrroline-5-carboxylate synthetase (P5CS; EC not assigned) is the rate-limiting enzyme in proline (Pro) biosynthesis in plants and is subject to feedback inhibition by Pro. It has been suggested that the feedback regulation of P5CS is lost in plants under stress conditions. We compared Pro levels in transgenic tobacco (Nicotiana tabacum) plants expressing a wild-type form of Vigna aconitifolia P5CS and a mutated form of the enzyme (P5CSF129A) whose feedback inhibition by Pro was removed by site-directed mutagenesis. Transgenic plants expressing P5CSF129A accumulated about 2-fold more Pro than the plants expressing V. aconitifolia wild-type P5CS. This difference was further increased in plants treated with 200 mM NaCl. These results demonstrated that the feedback regulation of P5CS plays a role in controlling the level of Pro in plants under both normal and stress conditions. The elevated Pro also reduced free radical levels in response to osmotic stress, as measured by malondialdehyde production, and significantly improved the ability of the transgenic seedlings to grow in medium containing up to 200 mM NaCl. These findings shed new light on the regulation of Pro biosynthesis in plants and the role of Pro in reducing oxidative stress induced by osmotic stress, in addition to its accepted role as an osmolyte.

Growth Characteristics, Physiological and Metabolic Responses of Teak (Tectona Grandis Linn. f.) Clones Differing in Rejuvenation Capacity Subjected to Drought Stress

“…The content of proline, a protective solute in teak leaves increased due to drought treatment in both the clones studied. Proline is an amino acid and known to act as an osmolyte, protecting the plasma membrane integrity (MANSOUR, 1998), as a sink of energy or reducing power (VERBRUGGEN et al, 1996), as a scavenger of ROS and their derivatives (HONG et al, 2000;BASHIR et al, 2007) and as a source for carbon and nitrogen (PENG et al, 1996), and thereby helping the plants to tolerate stress effects (MANIVANNAN et al, 2007). In the present teak clonal materials proline accumulation thus appears to be related to mechanisms associated with tolerance to desiccation (MANIVANNAN et al, 2007).…”

Whole-Genome Mapping of Agronomic and Metabolic Traits to Identify Novel Quantitative Trait Loci in Bread Wheat Grown in a Water-Limited Environment

“…Similarly, the accumulation and maintenance of a high sugar pool containing nonreducing sugars and oligosaccharides has been reported to act as a replacement for water by providing a hydration shell around proteins. Although there is evidence from some previous studies that enhanced accumulation of Pro (Hong et al, 2000) and sugars (Hoekstra et al, 2001;Bogdan and Zagdanska, 2006;Urano et al, 2009) improves the osmotic stress tolerance of plants, there have also been reports that the accumulation of organic compatible solutes makes only minor contributions to osmotic stress tolerance (Gagneul et al, 2007;Hill et al, 2013). Here, metabolites of Glu and Pro metabolism (including Gln, Orn, Arg, and 5-oxo-Pro) and sugar metabolism (raffinose, Fru, and Glc) were highly genetically correlated with grain yield and other yield-related agronomic traits.…”

Proline modulates the intracellular redox environment and protects mammalian cells against oxidative stress

“…Proline also has an established role in defending against various abiotic and biotic stresses with its properties as a compatible solute benefiting a broad-range of organisms [10][11][12][13][14][15][16][17][18][19][20]. Proline has been shown to diminish aggregation of the polyQ region of the huntington protein suggesting a preventive role of proline in neurodegenerative diseases [19].…”