Fig. 4

Transient expression of VdMYB1 in grapevine leaves affects defense responses. a Trypan blue stained grapevine leaves inoculated with E. necator at 6 dpi. OE VdMYB1 #1, OE VdMYB1 #2, OE VdMYB1 #3 represent three independent replicates. b Number of conidiophores per colony of E. necator on grapevine leaves at 4 and 6 dpi. This method was used to quantify fungal growth on grapevine leaves. Error bars represent SD of three independent biological replicates (n = 30). c Kinetics of reactive oxygen species (ROS) production monitored over 60 min in leaf challenge with E. necator. Error bars represent SD of three biological replicates. d-f Expression of defense-related genes in VdMYB1-overexpressing leaves and mock leaves. Relative transcript levels of VdPR1, VdPDF1.2, and VdSTS2 were examined at various times using qRT-PCR. The VdGAPDH gene was used as an internal control. Error bars represent SD of three biological replicates per genotype and time -point. Hpi, hours post inoculation. g Measurement of trans-resveratrol content in mock and VdMYB1-overexpressing leaves after pathogen infection using high- performance liquid chromatography (HPLC). Mock: leaves infiltrated with Agrobacterium carrying no vector. The data represent means ± SD of three independent experiments. Asterisks indicate statistically significant differences (*P < 0.05, **P < 0.01)