Development and application of different strategies for increasing fire blight resistance in susceptible varieties of apple (cv.Golden Deliciuos and cv.Royal Gala)

Supervisor: Dr Riccardo Velasco (FEM)

Co-supervisor: Dr Mickael Arnaud Malnoy (FEM)

Apple is one of the most common fruits and its worldwide production represents about the 12% of total fruit and vegetables crops. In the last decade, its cultivation has been consederably affected by Fire blight (FB), a contagious bacterial disease caused by the Gram-negative bacteria Erwinia amylovora that infects apples, and leads to remarkable reduction in fruit production. This disease is currently controlled with the massive use of a mix of cultural practice and application of copper compounds and antibiotics, which has considerable economic costs as well as a negative impact on environment, human health, and public perception. Therefore the use of resistant apple varieties is a cost-efficient way to control apple FB. Since the genome of apple was sequenced, many efforts have been made by researchers in order to highlight host-pathogen interactions during FB infection and to identify resistance and susceptible host genes.
On the basis of this knowledge, the PhD project aims to develop and apply new strategies for improving FB resistance in susceptible varieties of apple, focusing the attention on different plant molecular mechanisms which are proved to be relevant in FB infection as follows:

1) In plant cell, Ca2+ plays a central role as a second messenger in response to various endogenous and external stimuli and its cytosolic concentration is regulated by calcium-dependent protein kinases (CDPKs). Recent studies revealed the involvement of CDPKs in Malus blossom–Erwinia interaction and the MdCPK19 gene as a good candidate since its expression is induced in FB resistant apple cultivars. Therefore to study the potential role of this molecule in FB resistant, the molecular characterization, pathogen infection, [Ca2+]cyt assessment and transcriptome analysis of tansgenic lines of Malus cv.Royal Gala overexpressing MdCPK19 will be conducted.

2) miRNAs are essential gene expression regulators and they play a key role in a great variety of stress conditions including pathogen infections. Recently, many apple miRNAs was shown to be involved in FB resistance. Among these, Md-mir285 targets at least 17 deseases resistance genes including CDPKs and all NPR genes which control the onset of systemic acquired resistance. On this basis, plants of Arabidopsis thaliana and Malus cv. Royal Gala will be transformed to overexpress and silence Md-mir285 and subsequently characterized. The study of Md-mir285 promoter will be also performed.

3) Erwinia amilovora secrete 8 pathogenicity effectors, such as DspA/E, which interact with four Malus proteins (DIPM 1-4). DIPMs can be considered as susceptible genes as their expression is strongly increased during the infection. To increase FB resistance in Malus, a genome editing approach via CRISPR/Cas9 will be used to obtain cisgenic lines silencing DIPM4.

Biography and contacts

Valerio Pompili was born in 1990 in Rome. In 2012 he graduated in Human Nutrition and Food Science at the ‘University Campus Bio-medico of Rome’ where he also achieved in 2015 a Master Degree in Food Technology, spending his final research internship at the ‘Edmund Mach Foundation’ and studying the role of the ethylene responsive factor VviERF045 in fruit ripening of Vitis vinifera. In 2016 he spent ten months at the ‘University of Roma Tre’ analyzing the role of the Arabidopsis thaliana polyamine oxidase 5 in root development and in response to abiotic stress. In October 2016 he won a PhD position at the ‘University of Udine’ and he his currently carrying his project on in the laboratory of Genomics and Advanced Biology at the ‘Edmund Mach Foundation’.

Contacts:
E-mail: valerio.pompili@guests.fmach.it, pompili.valerio@spes.uniud.it
Phone: +39 0461 615231