Accumulation of lead in the roots of grass pea (Lathyrus sativus L.) plants triggers systemic variation in gene expression in the shoots

The impact of lead nitrate (Pb(NO3)2; 0.5 mM) on steady-state accumulation of messengers corresponding to stress responsive genes was studied in two local lines of 11-d grass pea (Lathyrussativus L.) plants exposed for 96 h in a hydroponic system. Real-time reverse transcription polymerase chain reaction technique was used with grass pea-specific primers designed from newly isolated partial cDNA. Increases in accumulation of glutathione reductase, ascorbate peroxidase and glutathione S-transferase transcripts suggested that roots enhanced detoxification mechanisms involving glutathione. In the leaves where no lead was translocated, the pollutant indirectly triggered increases in expression of several genes. This process probably resulted from systemic signals originating from the roots where lead accumulated in large amounts, approximately 150 mg Pb g−1 dry weight. A preventive and/or adaptive role for the signal is assumed, since it concerned genes implicated in reactive oxygen species scavenging (ascorbate peroxidase), protein protection (heat shock protein 70) and proteolysis (cysteine and aspartic proteases).