Co-Evolution of Mitochondrial tRNA Import and Codon Usage Determines Translational Efficiency in the Green Alga Chlamydomonas

in PLoS Genetics (2012), 8(9),

The elicitation of a systemic resistance by Pseudomonas putida BTP1 in tomato involves the stimulation of two lipoxygenase isoforms

in BMC Plant Biology (2011), 11

Background Some non-pathogenic rhizobacteria called Plant Growth Promoting Rhizobacteria (PGPR) possess the capacity to induce in plant defense mechanisms effective against pathogens. Precedent studies ... [more ▼]

Background Some non-pathogenic rhizobacteria called Plant Growth Promoting Rhizobacteria (PGPR) possess the capacity to induce in plant defense mechanisms effective against pathogens. Precedent studies showed the ability of Pseudomonas putida BTP1 to induce PGPR-mediated resistance, termed ISR (Induced Systemic Resistance), in different plant species. Despite extensive works, molecular defense mechanisms involved in ISR are less well understood that in the case of pathogen induced systemic acquired resistance. Results We analyzed the activities of phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX), key enzymes of the phenylpropanoid and oxylipin pathways respectively, in tomato treated or not with P. putida BTP1. The bacterial treatment did not stimulate PAL activity and linoleate-consuming LOX activities. Linolenate-consuming LOX activity, on the contrary, was significantly stimulated in P. putida BTP1-inoculated plants before and two days after infection by B. cinerea. This stimulation is due to the increase of transcription level of two isoforms of LOX: TomLoxD and TomLoxF, a newly identified LOX gene. We showed that recombinant TomLOXF preferentially consumes linolenic acid and produces 13-derivative of fatty acids. After challenging with B. cinerea, the increase of transcription of these two LOX genes and higher linolenic acid-consuming LOX activity were associated with a more rapid accumulation of free 13-hydroperoxy-octadecatrienoic and 13-hydroxy-octadecatrienoic acids, two antifungal oxylipins, in bacterized plants. Conclusion In addition to the discovery of a new LOX gene in tomato, this work is the first to show differential induction of LOX isozymes and a more rapid accumulation of 13-hydroperoxy-octadecatrienoic and 13-hydroxy-octadecatrienoic acids in rhizobacteria mediated-induced systemic resistance. [less ▲]

Systemic resistance induction by Pseudomonas putida BTP1 in tomato: investigation of defense pathways

Poster (2009, May 07)

Systemic resistance induction in tomato by Pseudomonas putida BTP1: investigation of defense pathways.

in Journal of Plant Pathology [=JPP] (2008), 90

The systemic resistance induced in tomato by a non-pathogenic Pseudomonas strain is associated with the stimulation of the lipoxygenase pathway

in Bulletin OILB/SROP = IOBC/WPRS Bulletin (2007), 30

Root treatment by the non-pathogenic Pseudomonas putida strain BTP1 reduced by 34% the disease caused by Botrytis cinerea on tomato leaves. This induced systemic resistance phenomenon is associated both ... [more ▼]

Root treatment by the non-pathogenic Pseudomonas putida strain BTP1 reduced by 34% the disease caused by Botrytis cinerea on tomato leaves. This induced systemic resistance phenomenon is associated both with the accumulation of fungitoxic material and with the stimulation of the lipoxygenase pathway in infected leaves. More precisely, we observed a consistent change in the expression of a new tomloxF gene in the leaves from BTP1-treated plants as far as the pathogen is introduced. This suggests that the roots were primed and reacted locally to colonization by bacteria and that defense-related gene expression is turned on systemically upon pathogen perception [less ▲]

The lipoxygenase pathway as defence mechanism against fungal disease specifically stimulated in tomato plants by a non-pathogenic Pseudomonas putida

Poster (2006, May 17)

Bacillus subtilis M4 decreases plant susceptibility towards fungal pathogens by increasing host resistance associated with differential gene expression

in Applied Microbiology & Biotechnology (2005), 67(5), 692-698

Results presented in this paper describe the ability of Bacillus subtilis strain M4 to reduce disease incidence caused by Colletotrichum lagenarium and Pythium aphanidermatum on cucumber and tomato ... [more ▼]

Results presented in this paper describe the ability of Bacillus subtilis strain M4 to reduce disease incidence caused by Colletotrichum lagenarium and Pythium aphanidermatum on cucumber and tomato, respectively. Disease protection in both pathosystems was most probably due to induction of resistance in the host plant since experiments were designed in order to avoid any direct contact between the biocontrol agent and the pathogen. Pre-inoculation with strain M4 thus sensitised both plants to react more efficiently to subsequent pathogen infection. In cucumber, the use of endospores provided a disease control level similar to that obtained with vegetative cells. In contrast, a mixture of lipopeptides from the surfactin, iturin and fengycin families showed no resistance-inducing potential. Interestingly, treatment with strain M4 was also associated with significant changes in gene transcription in the host plant as revealed by cDNA-AFLP analyses. Several AFLP fragments corresponded to genes not expressed in control plants and specifically induced by the Bacillus treatment. In support to the macroscopic protective effect, this differential accumulation of mRNA also illustrates the plant reaction following perception of strain M4, and constitutes one of the very first examples of defence-associated modifications at the transcriptional level elicited by a non-pathogenic bacterium in a host plant. [less ▲]

Resistance induced in cucumber and tomato by a non-pathogenic Pseudomonas putida strain

in Parasitica (2005), 61

Some plant growth promoting rhizobacteria are able to stimulate inducible defense mechanisms that render the host plant less susceptible to a subsequent pathogen attack. This phenomenon, called induced ... [more ▼]

Some plant growth promoting rhizobacteria are able to stimulate inducible defense mechanisms that render the host plant less susceptible to a subsequent pathogen attack. This phenomenon, called induced systemic resistance (ISR), can occur in several plant species against a wide range of bacterial, viral and fungal pathogens. Despite extensive work, many aspects of the molecular basis underlying this rhizobacteria-mediated ISR remain unclear. In this context, we have studied for several years the ISR-mediated protective effect of a particular strain, Pseudomonas putida BTP1. In this paper, we present the results obtained by using BTP1 for disease reduction against anthracnose caused by Colletotrichum lagenarium on cucumber and grey mold caused by Botrytis cinerea on tomato. As a result of cucumber treatment with BTP1, we observed an enhanced hydroperoxide lyase activity that could restrict pathogen ingress since this enzyme, acting downstream in the so-called oxylipin pathway, forms short chain aldehydes considered as “volatile phytoalexins”. By contrast, this phenomenon is not involved in the protective effect afforded by the strain in tomato. In this case, disease reduction is more seemingly associated with an early accumulation of antifungal compounds stimulated by the bacterium, showing that specific ISR-related metabolic pathways may be activated in different plants by the same microorganism. [less ▲]

Differential gene expression in cucumber plants showing induced systemic resistance

Poster (2003, July)

Mutations Inactivating Mitochondrial Genes in Chlamydomonas Reinhardtii

in Biochemical Society Transactions (2001), 29(Pt 4), 442-6

Chlamydomonas reinhardtii is now becoming a useful model for the study of mitochondrial genetics in a photosynthetic organism. The small (15.8 kb) mitochondrial genome C. reinhardtii has been sequenced ... [more ▼]

Chlamydomonas reinhardtii is now becoming a useful model for the study of mitochondrial genetics in a photosynthetic organism. The small (15.8 kb) mitochondrial genome C. reinhardtii has been sequenced completely and all the genes have been identified. Several mutants inactivated in mitochondrial genes encoding components of the respiratory complexes I, III and IV have been characterized at the molecular level. Assembly of complex I in several mutant strains and mapping of mitochondrial mutations by recombinational analysis are also described. [less ▲]