THE ROLE OF ABSCISIC ACID IN STRESS TOLERANCE

Mosses have evolved complex mechanisms to overcome abiotic stresses. The phytohormone abscisic acid (ABA) plays an important role in the establishment of stress tolerance in vascular plants as well as in bryophytes. ABA pre-treatment greatly enhances tolerance to dehydration, cold temperature and osmotic stresses in the moss Physcomitrella patens. The response to abiotic stresses and ABA in P. patens is accompanied by the accumulation of sugars along with morphological and physiological changes. Some of the genes regulated by ABA in P. patens are also controlled by the ABA-signalling pathway in vascular plants. However, there are genes expressed in response to ABA and abiotic stress in P. patens that are not found in seed plants. With the ability to easily delete and replace genes by homologous recombination, as well as a fully sequenced and assembled genome, P. patens will provide an excellent model for studying stress biology in plants.