Submergence induces expansin gene expression in flooding-tolerant Rumex palustris and not in flooding-intolerant R-acetosa

Ethylene-enhanced leaf elongation upon submergence is part of the survival mechanism of Rumex palustris Sm. plants that grow in frequently flooded are as. Other Rumex species, like R. acetosa L., do not possess this ability an d can therefore only survive in habitats that are not frequently inundated. Expansins are proteins that induce extension of isolated cell walls, and t herefore might play a role in the stimulation of petiole elongation, also i n Rumex. We report here on the identification of several gene sequences enc oding for alpha-expansins in R. palustris and R. acetosa plants. The patter n of transcript accumulation of one of these genes, Rp-EXP1, could be corre lated with the pattern of leaf elongation in R. palustris after submergence or ethylene treatment. Induction of expansin gene activity was not found i n R. acetosa upon these treatments, indicating that ethylene induces the ex pression of expansin genes in leaves of species that exhibit flooding-induc ed shoot elongation.