Submitted to: Physiologia Plantarum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/18/1996
Publication Date: N/A
Interpretive Summary: The author presents a comprehensive view of the state of understanding of the mechanism of desiccation-tolerance employed by the poikilohydric species, Tortula ruralis. The manuscript contains a full treatise of earlier work and presents new data not previously presented. The work describes how this important species has evolved a mechanism to survive complete desiccation of its cells by activating the synthesis of certain proteins, rehydrins, upon rehydration of dried cells that speed the repair of the damage caused by this stress. The author presents new work that describes how this plant, and perhaps other species, prepare for rehydration by storage of important components during the drying phase. These components are rapidly released when water re-enters the dried cells. This is a comprehensive and peer reviewed article.
Technical Abstract: Plants that can withstand the desiccation of their vegetative tissues represent all but one class (the gymnosperms) within the kingdom Plantae. Desiccation-tolerant plants can be grouped into two categories; 1. poikilohydric: plants whose internal water content rapidly equilibrates to the water potential of the environment and 2. Modified-poikilohydric: plants that all employ mechanisms to retard and control the rate of water loss. Desiccation-tolerance can be achieved by mechanisms that incorporate one of two alternatives, viz. cellular protection or cellular recovery (repair). Poikilohydric species, in particular the moss Tortula ruralis, appear to utilize a tolerance strategy that combines a constitutive protection system and a rehydration inducible recovery mechanism. The moss is capable of storing mRNAs during slow drying that are rapidly utilized upon rehydration presumably to speed recovery. Rapid dried moss has to rely yon rapid synthesis of the same mRNAs upon rehydration. Several "rehydrins" proteins whose synthesis is specific to the rehydration phase have been identified. Northern analysis of rehydrin cDNAs reconfirm the importance of translational controls in producing rehydrin proteins and an additional role of transcription and/or mRNA stability in the response of Tortula to desiccation. These studies indicate that there is more to desiccation- tolerance mechanisms that simple protection of the cells from drying, but rather rehydration induced events are important in the overall manifestation of this trait.