Plant basal resistance - Universiteit Utrecht

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Chapter 3 Bx1 contributes to penetration resistance against the necrotrophic fungus S. turcica To study the role of BXs in resistance against pathogens, we quantified levels of colonisation by the fungus S. turcica in leaves of Bx1 wild-type lines (Bx1 igl) and bx1 mutant lines (bx1 igl and bx1 Igl). This hemi-necrotrophic fungus penetrates the leaf tissue directly and colonises the leaf apoplast before inducing necrosis (Agrios, 1997; Chung et al., 2010). S. turcica- inoculated leaves were collected at 3 days post inoculation (dpi), stained with lactophenol trypan-blue, and examined for hyphal growth by light microscopy. In the progenies from both crosses, BX-deficient lines carrying the bx1 mutant alleles allowed significantly more hyphal growth than the BX-producing lines carrying the Bx1 wild-type alleles (Figure 3A). This difference in resistance was also reflected by the fraction of arrested spores in the epidermal cell layer, which ranged between 14% - 23% in bx1 mutant lines, to 47% - 49% in Bx1 wild-type lines (Figure 3B). Although the indole-producing bx1 lines from both crosses expressed marginally higher levels of resistance than the indole-deficient double mutant lines, this difference was not statistically significant (0.3 < P < 0.05). Hence, Bx1 contributes to slowing down and/or arresting S. turcica colonisation during the relatively early stages of infection, whereas the defensive contribution of Igl appears marginal at this stage. Figure 3: Contribution of Bx1 and Igl to penetration resistance against the necrotrophic fungus Setosphaeria turcica. Leaves of igl mutant lines, bx1 mutant lines, and bx1 igl double mutant lines were inoculated with 5 x 10 4 spores.mL -1 and 3 d later collected for lactophenol trypan-blue staining and microscopy analysis. A, Average hyphal lengths (μm) emerging from fungal spores (± SEM) in the epidermal cell layer. Different letters indicate statistically significant differences (ANOVA, followed by Fisher’s LSD test; α = 0.05; n=16). B, Frequency distributions between developing germination hyphae (class I; white) and arrested germination hyphae (class II; gray). Asterisks indicate statistically significant differences compared to BX-producing igl mutant lines from each cross (χ 2 test; α = 0.05; n = 16). The comparison between igl and bx1 igl mutant lines was repeated in two additional experiments with similar results. 70
71 Role of benzoxazinoids in maize immunity S. turcica elicits apoplastic BX accumulation during early stages of infection Based on our finding that Bx1-expressing plants express enhanced penetration resistance against S. turcica, we profiled levels of DIMBOA-glc, DIMBOA, and HDMBOA-glc from mock and S. turcica-inoculated wild-type plants. At the relatively early stage of 2 dpi, whole-tissue extracts from S. turcica-infected plants showed statistically increased levels of DIMBOA in comparison to mock-inoculated plants, whereas DIMBOA-glc and HDMBOA-glc remained similar between both treatments (Figure 4A). As observed during the interaction with R. padi (Figure 2A), apoplastic extracts from S. turcica-infected leaves showed a more dramatic response and contained significantly enhanced amounts of DIMBOA-glc, DIMBOA and HDMBAO-glc compared to mock-inoculated leaves (Figure 4B). By 5 dpi, BX profiles from S. turcica-infected leaves had changed, which coincided with the occurrence of disease symptoms. At this stage, S. turcica-inoculated leaves still produced more HDMBOA-glc than mock-inoculated leaves, but there was no longer a difference in DIMBOA-glc (Figures 4A-B). DIMBOA showed an even more dramatic increase than HDMBOA-glc, but was also more variable and not statistically significant in comparison to mock-treated leaves (Figures 4A-B). Hence, maize deposits increased levels of DIMBOA-glc, DIMBOA and HDMBOA-glc in the apoplast during the relatively early stages of S. turcica infection, and continues to accumulate HDMBOA-glc and DIMBOA during later symptomatic stages of the interaction. Figure 4: HPLC-DAD quantification of DIMBOA-glc, DIMBOA and HDMBOA-glc in whole tissue extracts (A) and apoplastic extracts (B) from mock- and S. turcica inoculated maize leaves. Material was collected at 2 d and 5 d post inoculation (dpi). 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). P values indicate levels of statistical significance.
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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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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: Aphid infestation stimulates apopla
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
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Page 102 and 103: Chapter 4 DISCUSSION The rhizospher
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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
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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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