Growth and protein profile changes in Lepidium sativum L. plantlets exposed to cadmium

Plant metabolic response to heavy metal stress is still to be clarified. The present investigation was undertaken to examine the influence of different concentrations of cadmium on the Lepidium sativum L. plantlets. Exposure of seedlings of L. sativum L. to increasing concentrations of cadmium results in the growth inhibition and in the accumulation of proteins in the 10-25 kDa range in cotyledons and hypocotyls of the plantlets. Most of these proteins are also found in extracts of L. sativum seeds. Analysis by ESI-MS after two-dimensional electrophoresis showed that these proteins exhibit sequences similar to those of storage proteins from various Cruciferae species. The response to metal exposure during germination and initial plantlet elongation thus involves inhibition of both storage protein catabolism and plant protein anabolism. In addition, two of the proteins present in higher amounts in plantlets exposed to cadmium heat-shock, in agreement with literature data, and jasmonate-like inducible protein are related to cellular stress and another two (LEAs or late embryogenesis abundant) are involved in embryogenesis. Changes in protein expression can be detected by two-dimensional electrophoresis after exposure to heavy metal concentrations lower than those at which morphometric changes become evident. Proteomics of germinating L. sativum thus constitutes a very sensitive tool for evaluating environmental pollution.