Tr288, A rehydrin with a dehydrin twist

The rehydrin Tr288, originally isolated from a screen for differentially expressed transcripts during rehydration of desiccated moss (Tortula ruralis), was further characterized. Steady-state mRNA levels for Tr288 increase dramatically during slow drying even though protein synthesis is completely inhibited during this process. Tr288 transcripts do not accumulate during rapid drying of moss gametophytes. Conversely, during rehydration of rapidly dried tissue Tr288 transcript levels increase several-fold, while the relatively high amount of Tr288 mRNA sequestered in slowly dried material declines with time after the addition of water. Steady-state Tr288 mRNA also increases after treatment with salt (NaCl) and elevated temperature (37 degreesC). Genomic Southern analysis and isolation of a genomic clone suggest the presence of a single Tr288 gene containing two introns within the T. ruralis genome. The only sequence homology detected by a BLAST search of GenBank occurred at the 3' end of the Tr288 coding region and indicated a single copy of the K segment common to dehydrins. Computer translation of the Tr288 coding region revealed 15 copies of a protein segment (the GPN segment) that is predicted to form amphipathic alpha -helices.