Botrytis cinerea(B.cinerea)causes grey mold disease in food crops and horticultural plants.B.cinerea is suspected to kill the plant cells via secreted toxins and derive nutrients from dead or dying cells,however whether B.cinerea induces necrosis or also triggering a programmed cell death(PCD)remains to be determined.We have previously partially characterized macromolecular phytotoxins(MPs)secreted by B.cinerea.Here we isolated MPs from B.cinerea culture and applied B.cinerea MP to Arabidopsis thaliana(A.thaliana)leaf cells and assessed the evidence of PCD over 120 hours.Cell death was assessed by propidium iodide(PI)and 4,6-diamidino-2-phenylindole(DAPI)staining.DNA fragmentation was assessed by agarose electrophoresis.Catalase(CAT)activity was assessed by monitoring H2O2 consumption by spectrophotometer,and Guaiacol peroxidase(POD)activity was measured colorimetrically with guaiacol.Isomers of POD were measured by the benzidine acetate method.The ratio of Cyt c/a was assessed by spectrophotometer.In A.thaliana exposed to B.cinerea MPs,we observed chromatin condensation and marginalization,nuclear substance leakage and DNA fragmentation.Furthermore,B.cinerea MPs induced release of cytochrome c from the mitochondria into the cytosol,and accumulation of autofluorescent materials in the cell wall.Moreover,CAT and POD activity was up-regulated and the POD isoenzyme pattern was altered.In conclusion,A.thaliana exposed to B.cinerea MPs exhibit multiple hallmarks of PCD,suggesting that B.cinerea induces PCD in host cells through secreted macromolecules.