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

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

MOLECULAR PLANT-MICROBE INTERACTIONS

AMER PHYTOPATHOLOGICAL SOC

Año: 2017 p. 46 - 60

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 immunity and 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, biphasic oxidative burst (O2.- and H2O2), HR response, accumulation of autofluorescent compounds, 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 and temporal program: firstly were induced in infiltrated leaflets (local acquired resistance, LAR), spreading out to lateral leaflets and later to distal untreated leaves (systemic acquired resistance, SAR). After AsES treatment, 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 idioblasts accumulating H2O2 and autofluorescent compounds that blast delivering its content unto surrounding 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.