Abstract
The phylloplane yeast Pseudozyma antarctica secretes an esterase, named PaE, and xylanase when cultivated with xylose. We previously observed that the lipophilic layer of Micro-Tom tomato leaves became thinner after the culture filtrate treatment. The leaves developed reduced water-holding ability and became wilted. In this study, the purified enzymes were spotted on Micro-Tom leaves. PaE, but not xylanase, thinned the lipophilic layer of leaves and decreased leaf resistance to the phytopathogenic fungus Botrytis cinerea. Disease severity increased significantly in detached leaves and potted plants treated with the culture filtrate and B. cinerea spores compared with those treated with inactivated enzyme and B. cinerea alone. Spore germination ratios, numbers of penetrating fungal hyphae in the leaves, and fungal DNA contents also increased significantly on the detached leaves. Japanese knotweed (Fallopia japonica), a serious invasive alien weed in Europe and North America, also became susceptible to infection by the rust pathogen Puccinia polygoni-amphibii var. tovariae following the culture filtrate treatment. The culture filtrate treatment increased disease development in plants induced by both phytopathogenic fungi. Our results suggest that P. antarctica culture filtrate could be used as an adjuvant for sustainable biological weed control using phytopathogenic fungi.
Highlights
Plants are exposed to various environmental stresses including infection by pathogenic microorganisms
The lipophilic layer was found to have been significantly thinned by treatment of either enzyme solution that contained active produce high amount of an esterase (PaE)
The lipophilic layer of samples treated separately with inactivated enzyme solution, and purified xylanase looks the same as that of samples treated with sterilized distilled water (SDW) (Fig. 1)
Summary
Plants are exposed to various environmental stresses including infection by pathogenic microorganisms. After being placed on the surfaces of leaves, spores produced cutinase in the development of disease, implying that cutinase has an important role in the penetration of the cuticle layer[20,21] From these reports, we considered that such leaves with damaged cuticles after the enzyme treatment would be prone to infection, and enhance the effectiveness of biocontrol agents. One of the candidate enzymes that had been developed as adjuvant to increase the effects of herbicides[22] might function as an adjuvant to enhance infection of rust spores into weed. A simple affinity purification method of cutinase-like enzymes was developed based on its BPs adsorption and degradation activities[24], which has made it possible to investigate the effect of high concentrations of purified PaE on leaves, as well as adjuvant effect on infection by biocontrol agents
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