Identification and molecular characterisation of elicitor-priming for resistance in tomato against <i>Botrytis cinerea</i>

Conventional crop protectants (fungicides) can lose their efficacy due to selection pressure for pathogen resistance caused by their widespread use¹. To date, there is a lack of genetic resistance in commercial crop varieties against necrotrophic fungal pathogens², such as <i>Botrytis cinerea</i>. The aggressive fungal pathogen <i>Botrytis cinerea</i> infects almost all vegetable and fruit crops³(&gt;1400 plant species), killing the host by inducing necrosis with degradation enzymes (virulence factors) and manipulating its host defences. Non-host inducing agents, such as elicitor molecules, are able to stimulate pathogen-induced defence mechanisms in the plant⁴and induce plant defences for increased and more efficient resistance (priming) against pathogens such as <i>B. cinerea</i>. Priming is based on a fine-tuned and enhanced resistance to biotic/abiotic stress that results in a faster and stronger expression of resistance upon pathogen attack⁵. This study aimed to identify candidate elicitors, determine their mode of action in the plant-<i>B.cinerea</i> interacion, characterise their molecular function and investigate a candidate elicitor role in priming tomato against <i>B.cinerea</i>. Resistance phenotypic assays have revealed that chitosan, a MAMP, was able to induced resistance in solanaceous crops <i>Solanum melongena</i>, <i>Nicotiana benthamiana</i>, <i>Solanum lycopersicum </i>and brassicaceous plant <i>Arabidopsis thaliana</i> by significantly decreasing necrotic lesion sizes and priming for callose deposition in a concentration-dependent manner. Furthermore, large-scale double (host/pathogen) transcriptomic analysis has unveiled that chitosan was able to prime 1,745 tomato transcripts during early and asymptomatic stages of <i>B. cinerea</i> infection. Transcriptome-based geneontology (GO) enrichment and HPLC/MS analyses revealed that chitosan-priming targets five main clusters, incuding 1) a higher cell sensitization throughout a faster and stronger transmembrane receptor/receptor-like kinase, CaBP and signal transducer activity; 2) a cell-wall reinforcement through R protein activation, cellulose synthesis and PGs, PMEs and xyloglucan repression; 3) a fine-tuned potentiation of JA/JA-Ile synthesis and JA/ET/SA/ABA transcriptional regulation; 4) an induction of the lipid/fatty acid metabolism and phenylpropanoid pathway; and 5) a strong repression of <i>B. cinerea </i>PGs, <i>BcSOD</i>, hexokinase and novel virulence factor uracil phosphoribosyltransferase (<i>BcUPRT</i>).Transcriptome analysis helped to the identification of two tomato novel and co-expressed genes,<i>SlACRE75 </i>and <i>SlACRE180</i>. Both transcripts and their <i>N. benthamiana</i> homologs were primed by chitosan early during infection and encode small proteins without a signal peptide and with unknown functions. Subcellular localization indicates that the four proteins are involved in intracellular/cytoplasmatic signalling. Finally, transient and constitutive overexpression of <i>SlACRE75</i>, <i>SlACRE180 </i>and their <i>N. benthamiana </i>homologs revealed that they are positive regulators of plant resistance against <i>B. cinerea</i>. Identification of specific chitosan-primed tomato pathways and genes such as <i>ACRE75 </i>and <i>ACRE180</i>; and <i>BcUPRT</i>, will provide a valuable resource for developing novel fungicide use strategies and engineering non-host resistance against necrotrophs in dicots.

Name dc:type.qualificationname

Doctor of Philosophy

Level dc:type.qualificationlevel

Doctoral Thesis

Grantor dc:publisher.institution

University of Dundee

Year dc:date.issued

2018

Author dc:creator

• De Vega Perez, Daniel

Advisor dc:contributor.advisor

• Stanley-Wall, Nicola

Language dc:language

eng

Identifier

oai:discovery.dundee.ac.uk:studenttheses/fbf46527-8ef7-4f80-8131-5e4c9a731151

OAI identifier oai:identifier

oai:discovery.dundee.ac.uk:studenttheses/fbf46527-8ef7-4f80-8131-5e4c9a731151