Journal
NEW PHYTOLOGIST
Volume 179, Issue 3, Pages 877-887Publisher
WILEY-BLACKWELL
DOI: 10.1111/j.1469-8137.2008.02480.x
Keywords
abscisic acid (ABA); Craterostigma plantagineum; desiccation tolerance; retrotransposon; siRNA
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Craterostigma plantagineum can lose up to 96% of its water content but fully recover within hours after rehydration. The callus tissue of the plant becomes desiccation tolerant upon pre-incubation with abscisic acid (ABA). In callus and vegetative organs, ABA addition and water depletion induce a set of dehydration-responsive genes. Previously, activation tagging led to the isolation of Craterostigma desiccation tolerant (CDT-1), a dehydration-related ABA-inducible gene which renders callus desiccation tolerant without ABA pre-treatment. This gene belongs to a family of retroelements, members of which are inducible by dehydration. Craterostigma plantagineum transformation with mutated versions of CDT-1 indicated that protein is not required for the induction of callus desiccation tolerance. Northern analysis and protoplast transfection indicated that CDT-1 directs the synthesis of a double-stranded 21-bp short interfering RNA (siRNA), which opens the metabolic pathway for desiccation tolerance. Via transposition, these retroelements have progressively increased the capacity of the species to synthesize siRNA and thus recover after dehydration. This may be a case of evolution towards the acquisition of a new trait, stimulated by the environment acting directly on intra-genomic DNA replication.
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