Plant basal resistance - Universiteit Utrecht

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Chapter 1 genetic resources for Arabidopsis (i.e. fully genotyped recombinant mapping populations or association mapping populations) to field experimentation. For instance, Arabidopsis mapping populations in which defence traits segregate could be grown under different field conditions with varying degrees of disease pressure by one or multiple pathogens and/or herbivores. Subsequent fitness evaluation may reveal defence-regulating QTLs that provide selective benefits under specified environmental conditions. With more and more Arabidopsis accessions being genome-sequenced, another promising approach arises from genome-wide association mapping approaches, which are based on associations between phenotypes and DNA sequence variants within individuals or isogenic populations (Nordborg and Weigel, 2008; Atwell et al., 2010). Particularly if defence phenotypes can be related to ecological stress parameters from the accessions’ geographical origins, this technique has the potential to assign measurable ecological significance to defence regulatory alleles. SECONDARY DEFENCE METABOLITES: BIOSYNTHETIC ORIGINS AND CHEMICAL CLASSIFICATION Irrespective of the type of <strong>resistance</strong> response expressed in plants, secondary metabolites are ubiquitous “tools” in plant defence. Figure 4 provides a generic overview of the biosynthesis pathways involved in the production of defence secondary compounds in plants. Unlike primary metabolites, which play a role in the process of photosynthesis, respiration, solute transport, nutrient assimilation and differentiation, secondary metabolites have no recognised role in plant processes that are essential for growth. The distribution of secondary metabolites across the plant kingdom is diverse and varies between plant species and taxa. Based on chemical structure, plant secondary metabolites can be divided into four major groups: terpenes, phenolics, nitrogen- and sulphur-containing compounds and oxyilipins. Figure 4 shows a generic overview of the different biochemical pathways controlling these plant compounds. Terpenes This class of metabolites is immensely diverse and includes more than 30,000 lipophilic compounds (Kennedy and Wightman, 2011). Their structure includes one or more 5-carbon isoprene (C 5 H 8 ) units, which are synthesized in plants by both the mevalonate and dexy-d- xylulose pathways (Rohmer, 1999). Classifications of terpenoids are based on the number of isoprene units they contain. Hemiterpenes incorporate 1 isoprene unit, monoterpenes incorporate 2 units, sesquiterpenes incorporate 3 units, diterpenes incorporate 4 units, sesterpenes comprise 5 units, triterpenes include 6 units, and tetraterpenes incorporate 8 units. Terpenes exhibit a broad range of ecological roles in the plant kingdom. Their roles include antimicrobial properties, attraction of pollinator, parasitoic or predator insects, and 24
activities as allelopathic chemicals (De Almeida et al., 2010; Martino et al., 2010). Phenolics 25 General introduction Figure 4: A simplified scheme of the major biosynthetic pathways controlling plant secondary metabolites with representative examples and structures from each class. Secondary metabolites are derived from different pathways: the shikimate pathway, the malonic acid pathway, mavalonic acid pathway, the MEP/DOXP (2-C-methyl-D-erythritol 4-phosphate/1-deoxy-D-xylulose 5-phosphate) pathway, and the oxylipin pathway. Based on structural characteristics, the resulting secondary metabolites can be divided into four main classes: nitrogen (N) - and sulphur (S) containing compounds, phenolic compounds, terpenes, and oxylipins. Approximately 10,000 plant secondary metabolites are known to contain phenolic ring structures (Kennedy and Wightman, 2011). These are derivatives of the pentose phosphate pathway, the shikimate pathway, and the phenylpropanoid pathway. Structurally, natural phenolic compounds from plants have at least 1 aromatic hydrocarbon ring with one or more hydroxyl groups attached. Phenolics range from simple low molecular weight compounds like phenylpropanoids, coumarins, and benzoic acid derivatives, to more complex structures like flavanoids, stilbenes, and tannins. Phenolics play diverse roles in plant defence, such as responding to bacteria/fungal attack, providing scent/colour/flavour to attract beneficial insects/deter herbivores, and acting as semiochemicals during interactions with plant- beneficial microbes (Treutter, 2006). Sulphur and Nitrogen containing secondary metabolites This is a large group of secondary metabolites containing more than 15,000 molecules. They include alkaloids, cyanogenic glucosides, and non-protein amino acids. S- and N-containing
Page 1 and 2: Plant basal resistance: genetics, b
Page 3 and 4: Most of the research described in t
Page 5: Promotor: Prof. dr. Ir. C.M.J. Piet
Page 10 and 11: 10 CHAPTER 1 General Introduction A
Page 12 and 13: Chapter 1 (PRRs; Gomez-Gomez and Bo
Page 14 and 15: Chapter 1 by avirulent pathogens (R
Page 16 and 17: Chapter 1 Selective non-pathogenic
Page 18 and 19: Chapter 1 an endogenous plant signa
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Page 26 and 27: Chapter 1 metabolites are biosynthe
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Page 30: Chapter 1 latest insights. This Cha
Page 33 and 34: ABSTRACT 33 Genetic dissection of b
Page 35 and 36: 35 Genetic dissection of basal defe
Page 45 and 46: Natural variation in responsiveness
Page 57: 57 Genetic dissection of basal defe
Page 61 and 62: ABSTRACT 61 Role of benzoxazinoids
Page 63 and 64: 63 Role of benzoxazinoids in maize
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Page 69 and 70: Aphid infestation stimulates apopla
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75 Role of benzoxazinoids in maize
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Table S1: Primers used for RT-qPCR
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86 CHAPTER 4 Benzoxazinoids in root
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Chapter 4 INTRODUCTION Plants have
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Chapter 4 Our study presents eviden
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Chapter 4 Maize - P. putida FBC004
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Chapter 4 P. putida is tolerant to
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Chapter 4 Impact of DIMBOA on the P
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Chapter 4 PP5286 dut deoxyuridine 5
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Chapter 4 DIMBOA-producing wild-typ
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Chapter 4 DISCUSSION The rhizospher
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Chapter 4 patterns, we considered t
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108 CHAPTER 5 General Discussion
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Chapter 5 QTL was caused by a polym
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Chapter 5 Figure 1: CYP81D11 regula
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Chapter 5 et al., 2009), and allele
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Chapter 5 defence against different
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Chapter 5 occurred at time-points l
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Chapter 5 rhizospheric signals that
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Chapter 5 glucosinolate profiles. 1
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References References Abramovitch R
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References QTL mapping and characte
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References Gianoli E, Niemeyer HM (
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References Kliebenstein DJ, Kroyman
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References Studies in Natural Produ
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References Geniostoma antherotrichu
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References Todesco M, Balasubramani
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References Walters DR, Paterson L,
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Summary Summary Basal resistance in
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Samenvatting Samenvatting Basale re
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Samenvatting inzichten opgeleverd i
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Acknowledgments Acknowledgements In
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Curriculum vitae Shakoor was born o
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List of Publications Published arti
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