Abstract
Plants have immunity which is activated against broad range of microbes upon recognition of ‘non-self’ molecules called PAMPs （pathogen-associate molecular patterns） such as flagellin on bacterial flagella and chitin oligomer derived from fungal cell walls. However, pathogens have developed mechanisms to overcome this host immunity for successful infection. We have studied immune evasion mechanisms in fungal plant pathogens using an ascomycete rice pathogens Magnaporthe oryzae as a model. We have revealed that M. oryzae masked cell wall PAMPs with α-1,3-glucan, a non-degradable polysaccharide in plants. Indeed, M. oryzae mutant lacking α-1,3-glucan rapidly activated host immunity. Interestingly, ascomycete Cochliobolus miyabeanus and basidiomycete Rhizoctinia solani concealed cell wall PAMPs with α-1,3-glucan during rice infection. In supporting of this finding, transgenic rice plants secreting a bacterial α-1,3-glucanase became resistant to these fungal pathogens. Our finding suggested that a wide range of fungal pathogens use α-1,3-glucan for evading host immunity. Thus, α-1,3-glucan may be a efficient target to controlling various fungal diseases. Use of α-1,3-glucanase-producing bacteria and α-1,3-glucanse will have potential applications in sustainable crop protection techniques.
