Structure and regulation of an ABA- and desiccation-responsive gene from the resurrection plant Craterostigma plantagineum.

A gene from the resurrection plant Craterostigma plantagineum (CDeT6-19) encoding a protein with sequence similarity to a major group of late embryogenesis-abundant proteins (termed rab17, dehydrin or Lea D11) is regulated by abscisic acid (ABA) and desiccation. The corresponding transcript and protein is highly inducible in vegetative and callus tissue. To analyse the mechanism of CDeT6-19 regulation its promoter was fused to the beta-glucuronidase reporter gene (GUS) and introduced by PEG (polyethylene glycol) into protoplasts of Craterostigma or tobacco. With 889 bp of promoter sequence the GUS expression was significantly stimulated by ABA treatment in transient expression assays. ABA responsiveness was still observed with shorter promoter fragments, although they gave rise to lower GUS activities. Sequence comparisons with promoters from related genes of other species identified the conservation of potential ABA-responsive elements. In tobacco and Craterostigma plants stably transformed with CDeT6-19 promoter constructs a basal GUS activity is observed. However, GUS expression is enhanced by ABA or drying treatment of leaf tissues. In tobacco high promoter activity was observed in mature seeds (embryos) and in pollen.