Osmotic stress, proline accumulation

A frequently observed response of plant cells exposed to saline stress is the accumulation of proline. Two cell lines of tobacco, one resistant and the other sensitive to growth inhibition by NaCl, accumulated proline when exposed to 1.5% w/v NaCl in the growth media (Dix Pearce, 1981). The NaCl sensitive line accumulated proline more rapidly than did the resistant line, though the levels accumulated were not adequate to provide osmotic protection against salt stress. The authors suggested that proline accumulation may have a protective role other than osmoregulation and may be symptomatic of stress injury, the nature of which was not discussed. 

ProU, the other major transporter in these two species of bacteria, also has broad substrate specificities, with glycine betaine and proline betaine accumulated with particular efficiency. ProU is rapidly up-regulated by more than 100-fold during salt stress, and elevated expression of proU persists throughout the period of osmotic stress (Kempf and Bremer, 1998). 

Kravic N., Markovic K., Andelkovic V., Hadzi-Taskovic Sukalovic V., Babic V., Vu-lehc M. Growth, proline accumulation and peroxidase activity in maize seedlings under osmotic stress. Acta Physiologie Plantarum 2013 35 233-239. 

Barthakur, S., Babu, V., and Bansal, K.C., Over-expression of osmotin induces proline accumulation and confers osmotic stress tolerance in transgenic tobacco, J. Plant Biochem. BiotechnoL, 10, 31, 2000. 

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