Doctorate thesis of Montpellier 2 University
Monday, March 24, 2014
Functional expression of Plant Defensins type 1 for zinc tolerance in plants
Thi Ngoc Nga Nguyen
BPMP, “Metal phytotoxicity” team
Jury :
Dr. Martine DEVIC, DR CNRS, Présidente
Dr. Marc HANIKENNE, PR Université de liège, Rapporteur
Dr. Alain VAVASSEUR, DR CEA, Rapporteur
Dr. Sébastien THOMINE, DR CNRS, Examinateur
Dr. Pierre BERTHOMIEU, PR Montpellier SupAgro, Co-directeur de Thèse
Dr. Françoise GOSTI, CR CNRS, Co-directrice de Thèse
Abstract :
Plant Defensin type 1 (PDF1s) are mainly recognized for their response to pathogen attack via ethylene (Et) and jasmonate (JA) signaling activation pathway. However, PDF1s originating from Arabidopsis genus also showed their capacity to induce cellular zinc tolerance upon expression in yeast. A group of observations permitted to raise the hypothesis that increase in PDF1 transcript accumulation is necessary for their functional contribution to zinc tolerance in planta. Here, transcriptomic analysis (qRT-PCR) revealed that in both A. thaliana and A. halleri species, PDF1 paralogues were barely or not at all responsive to zinc although there was a specialization of PDF1s in response to activation of JA-signaling in the A. thaliana species. In addition, through a genetic approach performed in A. thaliana, the functional contribution of endogenous PDF1 members in zinc tolerance was directly demonstrated by examining combinations of T-DNA insertion knockout mutations and artificial miRNA expression. This genetic study also highlights the functional diversity among AtPDF1s as not all of them were showed to play a role in zinc tolerance. Indeed, a diversity of PDF1 molecular determinants for zinc tolerance in plants has been underlined. Remarkably, PDF1 high transcripts are not the only important parameter for zinc tolerance and PDF1 tissue specificity could be an important factor to consider too. Moreover, post-transcriptional and post-translational regulation might probably occur. Studies on these modifications are now the further questions in order to understand the contribution of the different PDF1s to zinc tolerance in planta.