Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: June 27, 1998
Publication Date: N/A
Technical Abstract: The South African grass Sporobolus stapfianus is a modified desiccation tolerant plant in that it can survive desiccation only if dehydration is relatively slow. This plant is the model in our studies to identify genes critical to desiccation tolerance. Differential display was used to detect gene transcript modulation during dehydration and rehydration in leaves of Sporobolus stapfianus. A 291 bp RT-PCR product was isolated and confirmed by northern analysis to be differentially expressed. This RT-PCR product was used to isolate a full length cDNA encoding a polypeptide of 210 amino acids with an apparent molecular weight of 26.5 kD. Sequence similarity searches show this cDNa, and predicted protein, to be similar to the Rab2 from mammalian and plant sources. GTP interactive motifs and a C-terminal isoprenylation site in the deduced protein sequence indicate it is a membrane attached GTP binding protein. The precise function of Rab2 is still unclear but in animal systems it is located in an intermediate compartment between the ER and golgi and involved with vesicle trafficking. Northern analysis of total RNA from leaves and roots of S. stapfianus showed that Rab2 transcrpt was present at basal levels in unstressed plants, accumulated throughout drying and again briefly during rehydration. Rab2 transcript was also present in leaves of the desiccation tolerant S. pellucidus and the desiccation sensitive S. pyramidalis, accumulating in both during drying and in S. pellucidus during rehydration. These results show that Rab2 accumulates in response to water stress in Sporobolus, but is not specific to desiccation tolerant plants, and while required for cell maintenance, a role in damage induced repair is possible.