Biology subjects

VERGNE, E.

Publications and source records attributed to VERGNE, E..

3 recordsLinked to original sources

bioRxiv2024

Dual NBT Approach: Gene Editing and Intragenesis to promote Fire Blight Resistance in Apple using MdAGG defense lectins.

Fire blight, caused by the bacterium Erwinia amylovora, represents a significant threat to apple (Malus domestica) production. Currently, only a limited number of genes effectively involved in resistance to E. amylovora have been identified. Seeking new resistance candidates, we focused on a multigene family encoding amaranthin-like lectins, which are highly upregulated following chemical elicitation by acibenzolar-S-methyl (ASM). These lectins are believed to contribute to downstream defense by promoting bacterial aggregation, which led to their designation as M. domestica agglutinins (MdAGG). When loss-of-function editions were introduced into MdAGG genes, the plants ability to mount a fully effective defense response against fire blight upon ASM treatment was compromised, confirming the role of MdAGGs in fire blight resistance. Next, we coupled the pPPO16 promoter, endogenous to apple and known to be rapidly induced during E. amylovora infection, with the coding sequence of MdAGG10 to create apple lines with fire blight-inducible MdAGG10 expression. Early MdAGG10 expression in these lines significantly improved resistance to fire blight, and an additional ASM treatment further enhanced this resistance. In summary, we conclude that MdAGGs act as defense genes whose timely expression can provide effective resistance against E. amylovora.

plant biology↗

bioRxiv2021

Phenotypic and transcriptomic analyses reveal major differences between apple and pear scab nonhost resistance

AO_SCPLOWBSTRACTC_SCPLOWNonhost resistance is the outcome of most plant/pathogen interactions, but it has rarely been described in Rosaceous fruit species. Apple (Malus x domestica Borkh.) have a nonhost resistance to Venturia pyrina, the scab species attacking European pear (Pyrus communis L.). Reciprocally, P. communis have a nonhost resistance to Venturia inaequalis, the scab species attacking apple. The major objective of our study was to compare the scab nonhost resistance in apple and in European pear, at the phenotypic and transcriptomic levels. Macro- and microscopic observations after reciprocal scab inoculations indicated that, after a similar germination step, nonhost apple/V. pyrina interaction remained nearly symptomless, whereas more hypersensitive reactions were observed during nonhost pear/V. inaequalis interaction. Comparative transcriptomic analyses of apple and pear nonhost interactions with V. pyrina and V. inaequalis, respectively, revealed differences. Very few differentially expressed genes were detected during apple/V. pyrina interaction, preventing the inferring of underlying molecular mechanisms. On the contrary, numerous genes were differentially expressed during pear/V. inaequalis interaction, allowing a deep deciphering. Pre-invasive defense, such as stomatal closure, could be inferred, as well as several post-invasive defense mechanisms (apoplastic reactive oxygen species accumulation, phytoalexin production and alterations of the epidermis composition). In addition, a comparative analysis between pear scab host and nonhost interactions indicated that, although specificities were observed, two major defense lines seems to be shared in these resistances: cell wall and cuticle potential modifications and phenylpropanoid pathway induction. This first deciphering of the molecular mechanisms underlying a nonhost scab resistance in pear offers new possibilities for the genetic engineering of sustainable scab resistance in this species. Concerning nonhost scab resistance in apple, further analyses must be considered with the aid of tools adapted to this resistance with very few cells engaged.

genomics↗

bioRxiv2021

Successful intergeneric transfer of a major apple scab resistance gene (Rvi6) from apple to pear and precise comparison of the downstream molecular mechanisms of this resistance in both species

BackgroundScab is the most important fungal disease of apple and pear. Apple (Malus x domestica Borkh.) and European pear (Pyrus communis L.) are genetically related but they are hosts of two different fungal species: Venturia inaequalis for apple and V. pyrina for European pear. The apple/V. inaequalis pathosystem is quite well known, whereas knowledge about the pear/V. pyrina pathosystem is still limited. The aim of our study was to analyse the mode of action of a major resistance gene of apple (Rvi6) in transgenic apple and pear plants interacting with the two scab species (V. inaequalis and V. pyrina), in order to determine the degree of functional transferability between the two pathosystems. ResultsTransgenic pear clones constitutively expressing the Rvi6 gene from apple were compared to a scab transgenic apple clone carrying the same construct. After inoculation in greenhouse with V. pyrina, strong defense reactions and very limited sporulation were observed on all transgenic pear clones tested. Microscopic observations revealed frequent aborted conidiophores in the Rvi6 transgenic pear / V. pyrina interaction. The macro- and microscopic observations were very comparable to the Rvi6 apple / V. inaequalis interaction. However, this resistance in pear proved variable according to the strain of V. pyrina, and one of the strains tested overcame the resistance of most of the transgenic pear clones. Comparative transcriptomic analyses of apple and pear resistant interactions with V. inaequalis and V. pyrina, respectively, revealed different cascades of molecular mechanisms downstream of the pathogen recognition by Rvi6 in the two species. Signal transduction was triggered in both species with calcium (and G-proteins in pear) and interconnected hormonal signaling (jasmonic acid in pear, auxins in apple and brassinosteroids in both species), without involvement of salicylic acid. This led to the induction of defense responses such as a remodeling of primary and secondary cell wall, lipids biosynthesis (galactolipids in apple and cutin and cuticular waxes in pear), systemic acquired resistance signal generation (in apple) or perception in distal tissues (in pear), and the biosynthesis of phenylpropanoids (flavonoids in apple but also lignin in pear). ConclusionThis study is the first example of a successful intergeneric transfer of a resistance gene among Rosaceae, with a resistance gene functioning towards another species of pathogen.

genomics↗