Submitted to: Desiccation Tolerance Workshop
Publication Type: Proceedings
Publication Acceptance Date: 1/6/1999
Publication Date: N/A
Interpretive Summary: Interpretive summary not required.
Technical Abstract: Desiccation-tolerant plants can be grouped into two categories: 1) the desiccation-tolerant plants whose internal water content rapidly equilibrates to the water potential of the environment and 2) the modified desiccation-tolerant plants that employ mechanisms to retard and control the rate of water loss. Desiccation tolerance can be achieved by mechanisms sthat incorporate one of two alternatives, viz. cellular protection or cellular recovery. The majority of plants utilize aspects of both. Desiccation-tolerant species, in particular the moss Tortula ruralis, appear to utilize a strategy that combines a constitutive protection system and a rehydration-inducible recovery mechanism. The recovery mechanism of T. ruralis relies heavily upon a change in gene expression that is mediated by post-transcriptional events. Within this response the synthesis of certain proteins are markedly affected. The synthesis of 25 proteins, termed hydrins, is terminated, or substantially decreased, and the synthesis of 74 proteins, termed rehydrins, is initiated, or substantially increased. Findings indicate that it takes a certain amount of prior water loss to activate the protein-based portion of the recovery mechanisms. Utilizing cDNAs representing individual hydrins and rehydrins, it was determined that if drying rates were slow (6h to dryness) rehydrin transcripts selectively accumulate in dried gametophytes. Studies revealed that this storage involves the formation of messenger riboneucleoprotein particles specific to dried tissues. These mRNPs aggregate under low salt conditions into particles of approximately 3700kD, 620kD and 110kD. We have demonstrated protein binding activity of the 3' region of the transcript for at least one rehydrin.