Submitted to: Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2005
Publication Date: 5/1/2005
Citation: Peng, C., Oliver, M.J., Wood, A. 2005. Is the rehydrin TrDr3 from tortula ruralis associated with tolerance to cold, salinity and reduced PH?. Plant Biology. 7: 315-320.
Interpretive Summary: In our search for genes involved in cellular dehydration tolerance we discovered a novel transmembrane protein gene from the desiccation tolerant moss Tortula ruralis that had some similarity to a known bacterial stress related protein. The moss protein has physical characteristics that are consistent with a transport protein and a phylogenetic and bioinformatics analysis revealed its similarity to the E.Coli protein HdeD. What was surprising is that this gene has no higher plant ortholog, it only has similarity to genes from other mosses. This is significant in that it may reveal a novel stress related gene and one that is more closely aligned to primitive mechanisms of tolerance. We established that the E. coli counterpart does confer stress resistance to bacteria, particularly to high pH and a combination of high pH, cold, and salinity. The functional aspects of the moss protein are currently the target of our ongoing investigation.
Technical Abstract: We have employed EST analysis in the resurrection moss Tortula ruralis to discover genes that control vegetative desiccation-tolerance and describe the characterization of the EST-derived cDNA TrDr3 (Tortula ruralis Desiccation-stress Related). The deduced polypeptide TRDR3 has a predicted molecular mass of 25.5 kDa, predicted pI of 6.7, and 6 trans-membrane helical domains. Preliminary expression analysis demonstrate that TrDr3 transcript ratio increases in response to slow desiccation relative the hydrated control in both total and polysomal mRNA (mRNP fraction) which classifies TrDr3 as a rehydrin. Bioinformatic searches of the electronic databases reveal that Tortula TRDR3 shares significant similarity to the hdeD gene product (HNS-dependent expression) from Escherichia coli. The function of the HdeD protein in E. coli is unknown, but it is postulated to be involved in a mechanism of acid-stress defense. To establish the role of E. coli HdeD in abiotic stress-tolerance, we determined the log survival percentage from shaking cultures of wild-type bacteria and the isogenic hdeD deletion strain ('hdeD) in the presence of low temperature (28' C), elevated NaCl (5% (w/v)), or decreased pH (4.5), or all treatments simultaneously. The 'hdeD deletion strain was less sensitive, as compared to wild-type E. coli, in response to decreased pH (P > 0.009), and the combination of all three stresses (P > 0.0001).