The elicitor protein AsES induces a SAR response accompanied by systemic microbursts and micro-HRs in Fragaria ananassa

HAEL CONRAD, VERONICA; PERATO, SILVIA MARISA; ARIAS, MARTA ELENA; MARTINEZ ZAMORA, MARTIN GUSTAVO; DI PETO, PIA DE LOS ANGELES; MARTOS, GUSTAVO GABRIEL; CASTAGNARO, ATILIO PEDRO; DIAZ-RICCI, JUAN CARLOS; CHALFOUN, NADIA REGINA

MOLECULAR PLANT-MICROBE INTERACTIONS

AMER PHYTOPATHOLOGICAL SOC

Año: 2017 vol. 23 p. 1 - 15

0894-0282

The elicitor AsES (Acremonium strictum Elicitor Subtilisin) is a 34 KDa subtilisin-like protein secreted by the opportunistic fungus Acremonium strictum. AsES activates the innate immunityand confers resistance against anthracnose and grey mold diseases in strawberry plants (Fragaria x ananassa Duch.) and the last disease also in Arabidopsis.In the present work, we show that upon AsES recognition, a cascade of defense responses is activated, including:calcium influx, biphasicoxidative burst (O2.-and H2O2), HR response, accumulation of autofluorescentcompounds, cell wall reinforcement with callose and lignin deposition,salicylic acid accumulation,and expression of defense-related genes such as FaPR1, FaPG1, FaMYB30, FaRBOH-D, FaRBOH-F, FaCHI23 and FaFLS. All these responses occurred following a spatial andtemporal program: firstlywere induced in infiltrated leaflets(local acquired resistance, LAR), spreading out to lateral leafletsand later to distal untreated leaves (systemic acquired resistance, SAR).After AsEStreatment, macro-HR and macro oxidative bursts were localized in infiltrated leaflets while micro-HRs and microbursts occurred later in untreated leaves, being confined to a single cell or a cluster of few epidermal cells that differentiate from the surrounding ones.The differentiated cells initiate a time dependent series of physiological and anatomical changes, evolving to idioblastsaccumulatingH2O2 and autofluorescent compoundsthat blast deliveringits content untosurrounding cells. This kind of systemic cell death process in plants is described for first time in response to a single elicitor. All data presented in this study suggest that AsES has the potential to activate a wide spectrum of biochemical and molecular defense responses in F. ananassa what may explain the induced protection towards pathogens of opposite lifestyle like hemibiotrophic and necrotrophic fungi.