Characterization of Five Abscisic Acid-Responsive cDNA Clones Isolated from the Desiccation-Tolerant Plant Craterostigma plantagineum and Their Relationship to Other Water-Stress Genes.
Leaves of resurrection plants tolerate desiccation as do embryos of many higher plants. From the resurrection plant Craterostigma plantagineum a number of desiccation-related transcripts have recently been cloned; they are abundantly expressed in dried leaves and abscisic acid-treated dried callus (D Bartels, K Schneider, G Terstappen, D Piatkowski, F Salamini [1990] Planta 18: 27-34). Five distinct cDNA clones representing low copy number genes were selected for further characterization. Their nucleotide sequences were determined and proteins were predicted with a molecular mass between 16 and 34 kilodaltons. Three of these proteins have unusual amino acid compositions and extreme hydrophilic characters. Two of them contain a cluster of contiguous serine residues and lysine-rich repeats. These sequence motifs display homologies to desiccation-related genes expressed in embryos or dehydrated seedlings of several plants. A third cDNA clone contains tracts of sequences which are related to a cotton Lea (late embryogenesis abundant) gene (JC Baker, C Steele, L Dure III [1988] Plant Mol Biol II: 277-291). Secondary structure predictions are discussed and suggest that the deduced proteins could play a role in protecting core cell structures in a dehydrated cell. It is concluded that at least in part the gene products involved in the desiccation-induced pathways are common to leaves of resurrection plants and embryos. Two cDNA clones appear to code for Craterostigma-specific mRNAs. The expression patterns of all five transcripts were studied in comparison to desiccated leaves in dehydrated roots, in wound-stressed leaves and in salt-stressed callus. The data obtained point to the possibility that not only specificity of induction but also the expression level of specific gene products may be of importance for osmoprotection.
Piatkowski
D
D
Max-Planck-Institut für Züchtungsforschung, Carl-von-Linné-Weg 10, D-5000 Köln 30, Federal Republic of Germany.
Schneider
K
K
Salamini
F
F
Bartels
D
D