Abstract
Severe dehydration caused by abiotic stress such as freezing, desiccation and salinity stress gives irreversible damage to plant cells. We have been using the moss Physcomitrella patens as a model system to study mechanisms underlying injury caused by dehydration and signal-induced development of stress resistance at the cellular level. Protonema cells of P. patens acquire resistance to freezing and dehydration when treated with abscisic acid or hyperosmotic solutes, by undergoing drastic physiological changes such as accumulation of soluble sugars and expression of transcripts with similarity to higher plant stress-induced genes. The protonema cells also show rapid changes in organelle morphology characteristic to stress-resistant plant cells. These observations indicated that primary features necessary for stress resistance are conserved in moss and higher plant cells. Our recent studies employing transgenic approach indicated that the moss protonema cells are potentially useful for evaluation of stress tolerance conferred by exogenously introduced genes.
