Iron homeostasis and fire blight susceptibility in transgenic pear plants overexpressing a pea ferritin gene

UMR 1334 AGAP : Equipe AFEF ‘Architecture et Fonctionnement des Espèces fruitières’ ; Team AFFS ‘Architecture and Functioning of Fruit Species’ Contact: [email protected], [email protected] Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audienceThe bacterial pathogen Erwinia amylovora causes the devastating disease known as fire blight in some rosaceous plants including apple and pear. One of the pathogenicity factors affecting fire blight development is the production of a siderophore, desferrioxamine, which overcomes the limiting conditions in plant tissues and also protects bacteria against active oxygen species. In this paper we examine the effect of an iron chelator protein encoded by the pea ferritin gene on the fire blight susceptibility of pear (Pyrus communis). Transgenic pear clones expressing this gene controlled either by the constitutive promoter CaMV 355 or by the inducible promoter sgd24 promoter were produced. The transgenic clones produced were analysed by Q-RT-PCR to determine the level of expression of the pea transgene. A pathogen-inducible pattern of expression of the pea transgene was observed in sgd24-promoter transformants. Adaptation to iron deficiency in vitro was tested in some transgenic clones and different iron metabolism parameters were measured. No strong effect on iron and chlorophyll content, root reductase activity and fire blight susceptibility was detected in the transgenic lines tested. No transformants showed a significant reduction in susceptibility to fire blight in greenhouse conditions when inoculated with E. amylovor

Elimination of the nptII marker gene in transgenic apple and pear with a chemically inducible R/Rs recombinase

The efficient production of marker-free transgenic plants is still a challenge in most fruit species even though such plants are a necessary component of many "new breeding technologies", particularly cis- and intragenesis. Marker-free plant production is also necessary for the successive stacking of genes in an elite fruit transgenic line. Here, we used a R/Rs site-specific recombinase that is post-translationally regulated by dexamethasone through fusion with a ligand-binding domain for this hormone, and a bi-functional selectable marker gene coding for a cytosine deaminase/neomycin transferase (codA-nptII) protein; this enabled a first step of positive kanamycin selection, followed by a second step of negative 5-fluorocytosine selection. The aim of our study was to optimize this system on the apple cv. Galaxy and on the pear cv. Conference by conducting a detailed study of the effects of dexamethasone and 5-fluorocytosine treatments, and by comparing an early versus a delayed selection strategy. We were able to produce marker-free transgenic pear plants for the first time, and confirm the feasibility of producing marker-free transgenic apple plants using a chemically inducible recombinase system. We recommend the use of an early selection strategy for the pear cv. Conference and a delayed selection strategy for the apple cv. Galaxy

Effect of ectopic expression of the eutypine detoxifying gene Vr-ERE in transgenic apple plants

UMR 1334 AGAP : Equipe AFEF ‘Architecture et Fonctionnement des Espèces fruitières’ ; Team AFFS ‘Architecture and Functioning of Fruit Species’ Contact: [email protected] Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audienceThe development of alternative selection systems without antibiotic resistance genes is a key issue to produce safer and more acceptable transgenic plants. Eutypine is a toxin produced by Eutypa lata, the causal agent of eutypa dieback of grapevine, which is detoxified in mung bean (Vigna radiata) by the gene Vr-ERE. Many phytotoxic compounds containing an aldehyde group can act as substrates for the Vr-ERE enzyme. The aim of the present work was to evaluate the effects of the overexpression of Vr-ERE in transgenic apple plants, as a first step towards the development of an alternative selection system. Viable transgenic apple clones expressing Vr-ERE were produced from the cultivar Greensleeves under kanamycin selection. Although the Vr-ERE transgene was normally expressed at the RNA and protein levels, the increase in aldehyde reductase activity tested on a range of potential substrates was very low in these clones. None of them revealed a significant increase in tolerance to toxic aldehydes compared to their non-transgenic control. This work with transgenic apple plants overexpressing the detoxifying gene Vr-ERE illustrates some of the difficulties in developing an alternative selection pressur

Acibenzolar-S-Methyl Reprograms Apple Transcriptome Toward Resistance to Rosy Apple Aphid

International audienceAcibenzolar-S-methyl (ASM) is a chemical compound, which is able to induce resistance in several model and non-model plants, but the end-players of this induced defense remain ill-defined. Here, we test the hypothesis that treatment with ASM can protect apple (Malus × domestica) against the rosy apple aphid (Dysaphis plantaginea) and investigate the defense molecules potentially involved in resistance. We measured aphid life traits and performed behavioral assays to study the effect of ASM on plant resistance against the aphid, and then combined transcriptomic, bioinformatics, metabolic and biochemical analyses to identify the plant compounds involved in resistance. Plants treated with ASM negatively affected several life traits of the aphid and modified its feeding and host seeking behaviors. ASM treatment elicited up-regulation of terpene synthase genes in apple and led to the emission of (E,E)-α-farnesene, a sesquiterpene that was repellent to the aphid. Several genes encoding amaranthin-like lectins were also strongly up-regulated upon treatment and the corresponding proteins accumulated in leaves, petioles and stems. Our results link the production of specific apple proteins and metabolites to the antibiosis and antixenosis effects observed against Dysaphis plantaginea, providing insight into the mechanisms underlying ASM-induced herbivore resistance