Figure 2.

Role of jasmonic acid/ethylene (JA/ET) defence signalling cascades in β‐aminobutyric acid (BABA)‐induced resistance to Pectobacterium carotovorum ssp. carotovorum (Pcc). (A) Time course of PLANT DEFENSIN 1.2 (PDF1.2) expression in Arabidopsis on Pcc SCC1 infection. Arabidopsis plants were treated with water or BABA and challenged 48 h later with virulent Pcc SCC1 at a concentration of 5 × 10⁶ colony‐forming units (cfu)/mL. Leaves were harvested at 16, 18 and 24 h post‐inoculation (hpi). Transcript levels were determined by quantitative reverse transcription‐polymerase chain reaction (qRT‐PCR) and normalized to both UBQ10 and EF‐1. Relative gene expression levels were compared with water controls (defined value of one). Data represent the means and standard deviation (SD) of three independent biological replicates (n = 9). Values of BABA‐treated plants were not significantly different from those of water‐treated controls based on Student's t‐test (P < 0.01). (B) Pcc SCC1‐mediated symptoms of water‐ and BABA‐treated JA/ET signalling mutants. Five‐week‐old Arabidopsis plants were dip inoculated in 5 × 10⁶ cfu/mL P cc SCC1 and photographs were taken 16 h (ethylene‐insensitive 2‐1, ein2‐1) or 1 day (coronatine‐insensitive 1‐16, coi1‐16) later. White arrows indicate Pcc SCC1‐mediated water‐soaked lesions. (C) Pcc SCC1 titres in JA/ET signalling mutants. Water (W)‐ and BABA (B)‐treated plants were dip inoculated as in (B) and bacterial titres were evaluated at 1 day post‐inoculation (dpi). Average values ± SD from three independent experiments are presented (n = 9). Asterisks indicate a significant difference from water controls based on Student's t‐test (P < 0.05).