Abstract
Abscisic acid (ABA) is known to play an important role in responses to environmental stresses. We are investigating mechanisms of ABA-induced freezing tolerance in the moss Physcomitrella patens. ABA induced physiological changes such as expression of various genes, accumulation of boiling soluble proteins and increase in soluble sugar contents.
We isolated mutants with reduced ABA sensitivity by UV mutagenesis. These mutants grew normally in a medium containing ABA, whereas the wild type showed inhibited growth. Freezing and osmotic stress tolerance in these mutants was lower than that of wild type, but the extents of tolerance varied among the mutants. In these mutants, levels of expression of stress-related genes, a few boiling-soluble proteins and soluble sugars after ABA treatment were reduced as compared with those of wild-type. The degrees of freezing tolerance were correlated with levels of proteins and sugars in ABA-insensitive mutants.
