Plant basal resistance - Universiteit Utrecht

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Chapter 3 DIMBOA regulates transcriptional feedback inhibition of BX biosynthesis To elucidate further the involvement of the BX pathway in maize innate immunity, we profiled BX production and Bx gene expression after leaf infiltration with chitosan, a PAMP that is common in fungal cell walls and insect shells (Iritri and Faoro, 2009). At 24 h after infiltration with chitosan, whole-tissue extracts showed increased levels of HDMBOA-glc in comparison to mock-treated leaves (Figure 5A). Apoplastic extracts from chitosan-treated leaf segments displayed a more pronounced increase in DIMBOA and HDMBOA-glc (Figure 5B), thereby resembling the BX response to R. padi or S. turcica. Surprisingly, however, reverse-transcriptase quantitative PCR (RT-qPCR) analysis of Bx gene expression revealed reduced expression of Bx4, Bx5, Bx6, Bx7, Bx8 and Bx9 after treatment with chitosan (Figure 6A). To investigate whether this transcriptional repression is due to negative feedback inhibition from BX compounds, we profiled Bx gene expression after exposure to the volatile BX precursor indole. As is shown in Figure 6B, indole triggered similar patterns of Figure 5: HPLC-DAD quantification of DIMBOA-glc, DIMBOA and HDMBOA-glc in whole-tissue extracts (A) and apoplastic extracts (B) at 24 h after infiltration of leaf segments with 0.2% chitosan or mock buffer. Data represent means in μg.g -1 F.W. (± SEM) from three biologically replicated samples. Asterisks indicate statistically significant differences compared to mock-treated leaves (Student’s t-test; α = 0.05). The experiment was repeated twice with similar results. Bx gene repression as chitosan. Furthermore, comparison of Bx gene transcription between BX-producing igl single mutant lines and BX-deficient bx1 igl double mutant lines revealed enhanced Bx expression in BX-deficient plants (Figures 6C-D), providing further genetic evidence for transcriptional feedback inhibition. Since chitosan boosts accumulation of both DIMBOA and HDMBOA-glc in the apoplast (Figure 5B), we purified DIMBOA and HDMBOA- 72
73 Role of benzoxazinoids in maize immunity glc by preparative HPLC and examined which of both compounds is responsible for the feedback response. At 24 h after infiltration of the purified compounds in the leaf apoplast, DIMBOA repressed Bx gene expression in a dose-dependent manner (Figures 6E-F), whereas HDMBOA-glc had no statistically significant effect (Figure 6G). We, therefore, conclude that DIMBOA acts as an extracellular signal for transcriptional feedback of BX biosynthesis. Figure 6: Transcriptional feed-back regulation of the benzoxazinoid pathway by Bx1-dependent DIMBOA. Apoplastic infiltration with benzoxazinoid-inducing concentrations of chitosan (0.2 %) (A) and exposure to the volatile benzoxazinoid precursor indole (B) repressed Bx gene expression. benzoxazinoid-deficient bx igl double mutant lines displayed enhanced Bx gene transcription compared to benzoxazinoid-producing igl single mutant lines (C, D). Apoplastic leaf infiltration with DIMBOA (E, F) repressed Bx gene expression, whereas HDMBOA-glc had no effect (G), suggesting transcripitional feed-back regulation by apoplastic DIMBOA. Shown are average fold-change values (± SEM) of genes with a statistically significant level of induction (red) or repression (green) compared to mock treatments (A, B, E – G) or BX-producing igl single mutant lines (C, D). Differences in expression between three biologically replicated samples from independent experiments were tested for statistical significance, using Student’s t-tests or a non-parametric Wilcoxon Mann–Whitney test when values did not follow normal distributions (α = 0.05). n.d.: not determined. DIMBOA regulates callose deposition PAMP-induced callose deposition is commonly used as a marker for plant innate immunity (Luna et al., 2011). Chitosan elicits callose deposition in a wide variety of plants (Iritri and Faoro, 2009). To optimise this PAMP response in maize, we quantified callose after leaf infiltration with increasing concentrations of chitosan. At 24 h after infiltration, maize
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Plant basal resistance: genetics, b
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Most of the research described in t
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Promotor: Prof. dr. Ir. C.M.J. Piet
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10 CHAPTER 1 General Introduction A
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Chapter 1 (PRRs; Gomez-Gomez and Bo
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Chapter 1 by avirulent pathogens (R
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Chapter 1 Selective non-pathogenic
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Chapter 1 an endogenous plant signa
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Chapter 1 between defence signallin
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Page 24 and 25: Chapter 1 genetic resources for Ara
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
Page 67 and 68: Chemical treatments and callose qua
Page 69 and 70: Aphid infestation stimulates apopla
Page 71: 71 Role of benzoxazinoids in maize
Page 81 and 82: Table S1: Primers used for RT-qPCR
Page 86 and 87: 86 CHAPTER 4 Benzoxazinoids in root
Page 88 and 89: Chapter 4 INTRODUCTION Plants have
Page 90 and 91: Chapter 4 Our study presents eviden
Page 92 and 93: Chapter 4 Maize - P. putida FBC004
Page 94 and 95: Chapter 4 P. putida is tolerant to
Page 96 and 97: Chapter 4 Impact of DIMBOA on the P
Page 98 and 99: Chapter 4 PP5286 dut deoxyuridine 5
Page 100 and 101: Chapter 4 DIMBOA-producing wild-typ
Page 102 and 103: Chapter 4 DISCUSSION The rhizospher
Page 104 and 105: Chapter 4 patterns, we considered t
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Page 108 and 109: 108 CHAPTER 5 General Discussion
Page 110 and 111: Chapter 5 QTL was caused by a polym
Page 112 and 113: Chapter 5 Figure 1: CYP81D11 regula
Page 114 and 115: Chapter 5 et al., 2009), and allele
Page 116 and 117: Chapter 5 defence against different
Page 118 and 119: Chapter 5 occurred at time-points l
Page 120 and 121: 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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