ARS | Publication request: 472-THE TR288 REHYDRIN REPEAT STRUCTURE: IF ONE COPY'S GOOD, 15 MUST BE BETTER

Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 14, 1999
Publication Date: N/A

Technical Abstract: Tortula ruralis is a moss capable of surviving rapid drying of its vegetative tissue making it a fully desiccation-tolerant plant. Existing data suggest that the desiccation-tolerance mechanism(s) employed by T. ruralis are based upon rapid repair of cellular damage incurred upon rehydration. It is our working hypothesis that this repair of desiccation induced damage is facilitated by the activity of rehydrins, a group of proteins whose production is induced or enhanced upon rehydration. We have isolated and sequenced a number of rehydrin cDNA clones, one of which, Tr288, encodes a protein (deduced from DNA sequence) that shows no significant homology with any genbank entry, yet exhibits features similar to those of proteins known to be involved in desiccation and water stress responses (e.g. the dehydrin {DHN} - group 2 late embryogenesis abundant {LEA-g2} - responsive to absisic acid {RAB} family of proteins). For example, Tr288 has at it's carboxy terminus a single copy of the highly conserved "EKKGimdKIKEKLPG" (K-segment) motif of the DHN/LEA-g2/RAB family. TR288 is, however, distinguishable from other members of this family by the presence of fifteen copies of a unique fifteen amino acid repeated motif (the GPN-segment). Although the GPN-segment is, like the K segment, predicted by computer modeling to form an amphipathic alpha helix, the fact that both segments are present within Tr288 implies a different overall function for the GPN-segments. Examination of independent Tr288 genomic clones suggests that evolutionary pressure has resulted in several rounds of sequential DNA duplications of the GPN segments, implying a stoichiometric function for the motif.