Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 28, 1999
Publication Date: N/A
Technical Abstract: Tortula ruralis is a plant that can survive the complete loss of water from its vegetative cells; the most extreme drought, viz: desiccation. This plant achieves desiccation-tolerance by a mechanism that combines a constitutive level of cellular protection with a rehydration induced repair system. The rehydration induced repair and recovery process is facilitated by a change in gene expression that is mediated at the level of translatio and, if drying is slow, utilizes mRNA that is stored in mRNPs formed during drying. The stored mRNAs encode a group of proteins whose synthesis is essential to the re-establishment of cellular integrity. We have named these proteins rehydrins, a nomenclature based on function. We have cloned and sequenced a number of rehydrin cDNAs as well as a small but expanding desiccation/rehydration cDNA-EST database. Recent efforts have concentrated on three rehydrins; Tr155 encoding a putative alkyl-hydroperoxidase, Tr213 that encodes a plant polyubiquitin, and Tr288 that encodes a protein with no significant homology to any Genbank entry, yet has features similar to dehydrins. The predicted Tr288 protein contains 15 repeated motifs that are unrelated to Lea proteins yet it contains a single dehydrin K box segment at its carboxy end. We have transgenic tobacco that overexpress Tr288 and Tr155 and we are analyzing these plants for alterations in phenotype. Tr213 has been used to study the ubiquitin based protein turnover pathway and its response to desiccation and rehydration in both Tortula and a desiccation-tolerant angiosperm, Sporobolus stapfianus. We are presently attempting to establish a homologous recombination protocol for Tortula to enable us to study rehydrin gene function and promoter properties via gene replacement.