For expression analysis, 50 lL spore suspensions of B. cinereawere mixed with the same volume of EtOAc extracts of P. terrestris (200 lg/10 lL). In addition, suspensions of each pathogen were mixed with the same volume of acetone:water (1:9, v/v) as a control. The EtOAc extract was then mixed with the same volume of PDB to investigate the effects of P. terrestris EtOAc extract on the detached Arabidopsis thaliana leaf. Arabidopsis leaves of similar size and developmental stage were detached and placed abaxial side up on a wet Whatman filter paper in Petri dishes, after which they were inoculated by placing 10 lL the mixtures onto the middle of the leaves. The Petri dishes were then sealed with parafilm and incubated at 23 C under continuous light at 150 lmol/m2/s.
For qPCR analysis, leaves were harvested 12, 24, 48 and 72 h after inoculation. Lesion size was measured 48 and 72 h after inoculation. Six genes of B. cinerea and two genes of A. thaliana were analyzed using qPCR (Supplementary Table S2). Four genes of P.
cactorum were also analyzed by qPCR (Supplementary Table S2).