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Defense gene responses toward necrotrophic fungi in Arabidopsis thaliana

Peele, Hanneke Marjolijn (2015). Defense gene responses toward necrotrophic fungi in Arabidopsis thaliana. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2015:75
ISBN 978-91-576-8348-9
eISBN 978-91-576-8349-6
[Doctoral thesis]

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Leptosphaeria maculans an ascomycete in the diverse class of Dothideomycetes, is an devastating pathogen on Brassica crops. In this thesis, tools and knowledge in Arabidopsis thaliana was explored to enhance our knowledge on plant defense to this fungus. Mechanisms that to large extent are shared with other necrotrophic fungi. Plants have evolved disease resistance (R) genes encoding for nucleotide-binding site (NB) and leucine-rich repeat (LRR) proteins with N-terminals represented by either Toll/Interleukin-1 receptor (TIR) or coiled-coil (CC) domains. A genome-wide study of presence and diversification of CC-NB-LRR and TIR-NB-LRR encoding genes, and shorter domain combinations in 19 Arabidopsis thaliana accessions and Arabidopsis lyrata, Capsella rubella, Brassica rapa and Eutrema salsugineum were performed. Out of 528 R genes analyzed, 12 CC-NB-LRR and 17 TIR-NB-LRR genes were conserved among the 19 A. thaliana genotypes, while only two CC-NB-LRRs, including ZAR1, and three TIR-NB-LRRs were conserved when comparing the five species. The resistance to Leptosphaeria maculans 1 (RLM1) locus confers resistance to L. maculans and has experienced conservation and diversification events particularly in B. rapa. RLM3 is unique in comparison to other characterized R proteins due to its three brevis radix (BRX) domains adjacent to the TIR and the NB domains. Three homologs were found in Camelina sativa that diverged from Arabidopsis ~17 million years ago. The BRX domains is able to interact with RLM3 possibly signaling downstream signaling response after pathogen contact.

Two A. thaliana mutants, being susceptible to L. maculans (lms1 and lms5) were further characterized. LMS1 encodes a lipid phosphate phosphatase-like protein but lacks phosphatidic acid phosphatase activity. LMS1 is localized in the plasma membrane where it interacts through the third motif of the phospatidic phosphatase domain with the salicylic acid binding protein 3 (SABP3). SABP3 mutagenesis abolishes the interaction with LMS1. The lms1 mutant displays enhanced susceptibility to diverse pathogens, and high endogenous levels of SA and JA were found upon pathogen challenge. The LMS1-SABP3 interaction is central to maintain accurate JA and SA hormone homeostasis and defense signaling to necrotrophic pathogens. Mapping and genomic resequencing of the lms5 mutant revealed a mutation in a prolyl oligopeptidase (POP1) gene. POP1 interacts with the glycolate oxidase 1 protein, a regulator of hydrogen peroxide production. Upon fungal challenge levels of callose and indole-acetic acid (IAA) were elevated in lms5 compared to wild-type. The data highlight the importance of a balanced redox and auxin homeostasis to counteract invasion of L. maculans. In conclusion, this thesis work has revealed new defense genes, intricate interactions and signaling forming an important platform for future research and application in molecular breeding.

Authors/Creators:Peele, Hanneke Marjolijn
Title:Defense gene responses toward necrotrophic fungi in Arabidopsis thaliana
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :13 August 2015
Depositing date:13 August 2015
Number of Pages:43
IPeele HM, Guan N, Fogelqvist J, Dixelius C. (2014) Loss and retention of resistance genes in five species of the Brassicaceae family. BMC Plant Biol. 14:298
IIPeele HM, Bejai S, Montiel V, Dixelius C. The resistance gene landscape in An-1 and the importance of the BRX domains (manuscript).
IIIPeele HM, Bejai S, Oide S, Persson M, Guan N, Montiel V, Dixelius C. LEPTOSPHAERIA MACULANS SUSCEPTIBLE 1 modulates salicylic acid and jasmonic acid defense signaling to necrotrophic pathogens in Arabidopsis (manuscript).
IVBejai S, Guan N, Peele HM, Kaliff Stenberg M, Dixelius C. POP1, a prolyl oligopeptidase essential for the redox homeostasis in response to the fungus Leptosphaeria maculans (manuscript).
Place of Publication:Uppsala
Publisher:Department of Plant Biology, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-576-8348-9
ISBN for electronic version:978-91-576-8349-6
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:H Protection of plants and stored products > H20 Plant diseases
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Other Biological Topics
Agrovoc terms:arabidopsis thaliana, disease resistance, defense mechanisms, salicylic acids, leptosphaeria maculans, jasmonic acid, brassicaceae
Keywords:Arabidopsis thaliana, auxin, fungi, glycolate oxidase, jasmonic acid, Leptosphaeria maculans, propyl oligopeptidase, resistance genes, salicylic acid, salicylic acid binding protein 3, signaling
Permanent URL:
ID Code:12486
Faculty:NJ - Fakulteten för naturresurser och jordbruksvetenskap
Department:(NL, NJ) > Department of Plant Biology (from 140101)
External funders:FORMAS
Deposited By: HM Peele
Deposited On:14 Aug 2015 12:11
Metadata Last Modified:10 Sep 2020 13:41

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