Résumé
Tapping Panel Dryness (TPD) is a disease of rubber tree characterized by the reduction or total cessation of latex flow upon tapping, due to senescence of the laticifers leading to abnormal coagulation processes. The hypothesis of an oxidative stress-responsible for the damaging of the lutoid membrane is considered. Northern blot analysis showed that moderate ethylene treatment stimulated catalase, Mn-superoxide dismutase gene expression. However, overstimulation-indu ced TPD trees do not respond to ethylene, both in views of catalase and Mn-superoxide dismutase mRNA level and catalase activity. The overall results led to conclude that the modification of expression of catalase and Mn-superoxide dismutase genes in sick and healthy trees may be involved in the onset of overstimulation-induced TPD. Oxidative stress may not be involved in spontaneous TPD as no difference was observed in terms of catalase and Mn-superoxide dismutase transcripts level between sick and healthy trees. A full-length catalase cDNA from rubber tree latex was cloned and sequenced. It was found that the catalase cDNA consisted of1,476 nucleotides which encoded for a protein of 492 amino acids with molecular weight 56.7 kDa. Sequence comparison showed that this rubber tree catalase cDNA was highly homologous to several other plant catalases, in which the highest score of homology was the #R. communis#. catalase gene CAT1, with 89 and 91 % homology in nucleotides and amino acids, respectivel.