EXPRESSION OF A GREEN TISSUE-SPECIFIC 11 KDA PROLINE-RICH PROTEIN GENE IN BEAN IN RESPONSE TO HEAVY-METALS

A cDNA clone encoding a proline-rich protein specifically expressed in green tissues of bean has been isolated. This clone contains an open reading frame of 288 nucleotides coding for a putative protein of 96 a mino acids with an estimated molecular mass of 11 kDa, This protein, n amed PvPRP2, contains several specific amino acid motifs such as PPVYK and shows a high degree of sequence identity with the soybean SbPRP3. The PvPRP2 gene is constitutively expressed in stems and to a lesser extent in primary leaf tissue. In both tissues the cDNA probe hybridiz ed to a 600-nucleotide transcript. In root-tissues, where no 600-nucle otide transcript was delectable, the probe hybridized to a transcript of about 900 bp which was not found in green tissues, thus suggesting that both roots and green tissues contain specific PRPs. In contrast t o the green tissues genes, the expression of the root-gene is not alte red by heavy metal stresses. While transcripts were at low levels in u nstressed bean leaves, most of the abiotic stresses we have investigat ed (metals, wounding, drought, elevated temperature, UV,salt and ABA) triggered a strong response by increasing the expression of this gene. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.