Heavy Metal-responsive Genes in Kidney Bean: Cloulng of cDNAs and Gene Expression Anaiysis

Seven different cDNA framilies were isolated from a mereuric-chloride-treated bean (Phaseolus vulgaris L. )cDNA library by differential screening using cDNAs derived from treated and untreated plants. Transcriptionally activated cDNA clones are designated PvSR (Phaseolus vulgaris stress-related protein). The sequences of the cDNA inserts and homological analysis showed that they encode proline-rich protein (PvSR1 ), dehydrin (PvSR3 ), patho.,genesis-related protein (PvSR4), polyubiquitin (PvSR5 ), DnaJ-like protein (PvSR6) and two new HgCl2-stress-re-lated proteins (PvSR2 and PvSR7 )(Table 1 ). Northem blotting analysis revealed that the gene expression of PvSR2 and pathogenesis-related protein were strongly induced in leaf tissue by HgCl2stress, the transcript levels of prolinerich protein, dehydrin, polyubiqUitin,DnaJ-like protein and PvSR7 were greatly enhanced too (Fig. 1 ) , The various gene products might function to protect cell from heavy-metal stress.