Figure 3.

Expression of A. thaliana defense genes in response to ulvan. (a) RT-PCR analysis of PDF1.2, PR1a and PR5 expression in Col0, jar1.1, NahG and aba3.1 A. thaliana 5 days after ulvan treatment (ethanol-insoluble fraction, 1 mg · ml⁻¹). Data was normalized using β-Tubulin expression. Fold ratio is calculated with the corresponding control sample. Three biological replicates showed consistent results. (b) Fluorometric measures of GUS activities in leaves of transgenic Arabidopsis expressing a PR1::GUS fusion. Plants were infiltrated by water, ulvan (ethanol-insoluble fraction, 1 mg · ml⁻¹), or P2 (Phytophthora parasitica cell wall extract, 500 μg · ml⁻¹). GUS activity was determined 1 day post infiltration and quantified using fluorescent 4-methylumbelliferone as substrate. Mean and standard errors were calculated from three independent replicates. Specific activity is expressed as nkatal per mg of total proteins. Mean for each treatment was compared to the control mean using a Student's t-test. Treatment associated to a P-value ≤ .05 or ≤.01 was marked, respectively, by * or **.