Characterization of a desiccation-responsive small GTP-binding protein (Rab2) from the desiccation-tolerant grass Sporobolus stapfianus

• Published in: Plant molecular biology 1999-03, Vol.39 (4), p.809-821
• Main Authors: O'Mahony, P.J. (Plant Stress and Water Conservation Lab. USDA-ARS, Lubbock, TX (USA).), Oliver, M.J
• Format: Article
• Language: English
• Subjects: ABA; Amino Acid Sequence; Amino acids; Bacteria; Base Sequence; Conserved Sequence; DEHYDRATION; DESHIDRATACION; DESHYDRATATION; Desiccation; DNA, Complementary; E coli; Gene Library; Grasses; GTP-Binding Proteins - chemistry; GTP-Binding Proteins - genetics; GTP-Binding Proteins - metabolism; Leaves; Molecular Sequence Data; NUCLEOTIDE SEQUENCE; PCR; Poaceae - genetics; Poaceae - physiology; Protein Biosynthesis; Proteins; rab2 GTP-Binding Protein; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; REHIDRATACION; REHYDRATATION; REHYDRATION; Reverse Transcriptase Polymerase Chain Reaction; REVERSE TRANSCRIPTION; SECUENCIA NUCLEOTIDICA; Sequence Alignment; Sequence Homology, Amino Acid; SEQUENCE NUCLEOTIDIQUE; SPOROBOLUS; Sporobolus stapfianus; TRANSCRIPCION INVERSA; TRANSCRIPTION INVERSE; Transcription, Genetic; Water content
• ISSN: 0167-4412; 1573-5028
• DOI: 10.1023/A:1006183431854

We have used differential display to detect altering mRNA levels in response to desiccation and rehydration in leaves of the desiccation tolerant grass Sporobolus stapfianus. One of the RT-PCR products identified was used to isolate a cDNA of 999 bp which encodes a protein of 210 amino acids (predicted size 23 kDa). This protein displays considerable sequence similarity to mammalian and plant Rab2, a small GTP-binding protein, possessing several conserved motifs common to these regulatory proteins. Sporobolus Rab2 was expressed in Escherichia coli yielding a protein with an apparent molecular mass of ca. 30 kDa which was shown to have the ability to bind GTP. Rab2 transcript accumulated early in response to a decrease in relative water content (RWC) and remained high even in dried leaves. Rehydration of desiccated leaves resulted in a decrease in levels within 3 h of rewetting, with a brief increase at ca. 12 h. Accumulation of Rab2 transcript was also evident during drying and rehydration of the roots of S. stapfianus, as well as in leaves of the desiccation-sensitive grass Sporobolus pyramidalis. Earlier work on S. stapfianus concluded that the plant hormone ABA has little effect on inducing desiccation tolerance, however Rab2 transcript does exhibit a small increase in accumulation in response to exogenous ABA. A possible role for Rab2 with respect to desiccation tolerance and damage repair is discussed.