Induction of tcI 7, a gene encoding a β‐subunit of proteasome, in tobacco plants treated with elicitins, salicylic acid or hydrogen peroxide1

Abstract

We previously isolated, by differential display and 5′ RACE (rapid amplification of cDNA ends), cDNAs corresponding to genes activated following cryptogein treatment of tobacco cell suspensions, among them tcI 7 (tcI for obacco ryptogein nduced), a gene encoding a β-subunit of proteasome. Here, we report that tcI 7 was up-regulated in tobacco plants treated with elicitins (cryptogein and parasiticein) that have been shown to induce a systemic acquired resistance (SAR). Moreover, subsequent inoculation of tobacco with the pathogen Phytophthora parasitica var. nicotianae (Ppn) was shown to induce an additional activation of tcI 7 in tobacco plants pretreated with cryptogein. We also showed an up-regulation of tcI 7 by salicylic acid (SA). Moreover, accumulation of tcI 7 transcripts after treatment with cryptogein or with SA only occurred in NahG 9⁻ tobacco plants that do not express the salicylate hydroxylase and thus are able to accumulate SA and develop a SAR. Suppressed accumulation of tcI 7 transcripts in NahG 8⁺ tobacco plants after cryptogein or SA treatment correlated with the loss of SAR. H₂O₂ was also shown to up-regulate tcI 7 in tobacco plants. Using gene walking by PCR we cloned and sequenced the 5′ flanking region of tcI 7 containing hypothetical regulatory sequences, especially myb and NF-κB boxes, that could be responsible for the regulation of tcI 7 by salicylic acid and H₂O₂ respectively.