Article Figures & Data
Figures
- Figure 1.
Induction of Plant Defensins in Arabidopsis Wild-Type Plants (Col-0) and in the Ethylene Receptor Mutant etr1-1.
(A) RNA gel blots probed with either PDF1.2 or Tubulin β-1 (Tub) riboprobes. The samples represent 4 μg of total RNA.
(B) Plant defensin (PDF) contents as determined by ELISA, using an antigen affinity-purified anti–Rs-AFP1 (Raphanus sativus–antifungal protein 1) antiserum. Values are means (±se) of three independent determinations.
Arabidopsis plants were inoculated with A. brassicicola (A.bras.) by applying 5-μL drops of a spore suspension (5 × 105 spores per mL) on four lower rosette leaves (five drops per leaf). Control plants were treated identically with 5-μL drops of water (H2O). Pathogen-treated leaves (1°) and nontreated leaves of the same plants (2°) were collected 2 days after inoculation for RNA extractions and 3 days after inoculation for protein extractions. Total RNA and proteins were extracted as described in Methods. The experiment was repeated twice with similar results.
- Figure 2.
Three Alternative Models for the Interaction between Ethylene and Jasmonate Signals during Activation of the PDF1.2 Gene in Pathogen-Challenged Arabidopsis Plants.
Model 1 implies that pathogen infection initially stimulates production of ethylene, which subsequently stimulates production of jasmonates, which in turn activates PDF1.2. Model 2 implies that pathogen infection initially leads to enhanced production of jasmonates, which subsequently triggers elevated production of ethylene, which in turn controls PDF1.2 expression. Model 3 predicts that pathogen infection results in simultaneous production of ethylene and jasmonates, which are both required for induction of PDF1.2. The positions of the gene products EIN2 and COI in the different pathways are indicated by short arrows.
- Figure 3.
Time Course of Endogenous JA Content in Arabidopsis Wild-Type Plants (Col-0) and Ethylene-Insensitive Mutants (ein2-1) When Inoculated with A. brassicicola (Closed Symbols) or Mock Inoculated with Water (Open Symbols).
JA levels, expressed as nanograms of free JA per gram fresh weight of tissue, were determined by HPLC with extracts from Arabidopsis leaves collected 0, 12, 24, 36, 48, 60, 72, 84, and 96 hr after inoculation with 5-μL drops (five drops per leaf) of either an A. brassicicola spore suspension at 5 × 105 spores per milliliter or distilled water. Each data point is the average of measurements on two separate sets of three plants each. The experiment was repeated once with similar results.
- Figure 4.
Time Course of Ethylene Production Levels in Arabidopsis Wild-Type Plants (Col-0) and Jasmonate-Insensitive Mutants (coi1-1) When Inoculated with A. brassicicola (Closed Symbols) or Mock Inoculated with Water (Open Symbols).
Ethylene production, expressed as nanomoles of ethylene per hour per gram fresh weight of tissue, was determined 0, 12, 24, 36, 48, 60, 72, 84, and 96 hr after inoculation with 5-μL drops (five drops per leaf) of either an A. brassicicola spore suspension at 5 × 105 spores per milliliter or distilled water. Each data point is the average (±sd) of measurements on two separate sets of two plants each. The experiment was repeated twice with similar results.
- Figure 5.
Induction of Plant Defensins in Arabidopsis Wild-Type Plants (Col-0), Ethylene-Insensitive Mutants (ein2-1), and Jasmonate-Insensitive Mutants (coi1-1).
(A) RNA gel blots probed with either PDF1.2 or Tubulin β-1 (Tub) riboprobes. The samples represent 4 μg of total RNA. (B) Plant defensin (PDF) contents as determined by ELISA, using an antigen affinity-purified anti–Rs-AFP1 antiserum. Values are means (±se) of three independent determinations.
Arabidopsis leaves were inoculated with 5-μL drops (five drops per leaf) of water (con), paraquat (PQ; 25 μM), and MeJA (45 μM in 0.1% [v/v] ethanol). Ethylene treatment was performed by placing plants in an airtight chamber with an ethylene concentration of 50 ppm. All leaf samples were collected 48 hr after the initiation of treatment. The experiment was repeated two times with similar results.
- Figure 6.
Synergistic Induction of Plant Defensins by Ethylene and Jasmonate.
(A) RNA gel blots probed with either PDF1.2 or Tubulin β-1 (Tub) riboprobes. The samples represent 4 μg of total RNA.
(B) Plant defensin (PDF) contents as determined by ELISA, using an antigen affinity-purified anti–Rs-AFP1 antiserum. Values are means (±se) of three independent determinations.
Arabidopsis leaves from either agar-grown sterile plants or soilgrown nonsterile plants were inoculated with 5-μL drops (five drops per leaf) of MeJA (at the indicated concentration in 0.1% [v/v] ethanol) or 0.1% (v/v) ethanol (EtOH) either in the presence or the absence of ethylene (at the concentration indicated) in the atmosphere of an airtight chamber. All leaf samples were collected 48 hr after the initiation of treatment. The experiment was repeated three times with similar results.
- Figure 7.
ein2-1 and coi1-1 Plants Are Not Affected in Developmental Cues Influenced by Jasmonate and Ethylene, Respectively.
Wild-type (Col-0), ein2-1, and coi1-1 plants were grown under sterile conditions with a 12-hr photoperiod on Murashige and Skoog (MS) medium in the absence or presence of 100 μM MeJA (top). The same ecotypes were grown under sterile conditions in darkness in airtight containers in the absence or presence of 50 ppm ethylene in the atmosphere (bottom).
- Figure 8.
Three Distinct Responses Controlled by Ethylene and Jasmonate in Arabidopsis.
Ethylene is involved in the control of hypocotyl elongation and curvature and possibly in interactions with other hormones such as auxins, but not with jasmonates. Ethylene and jasmonates interact to regulate the expression of particular defense-related genes such as PDF1.2 upon pathogen perception. Jasmonates are involved in the control of root elongation, possibly in interaction with other hormones excluding ethylene.
