Autophagy restricts fungal accommodation in the roots of Arabidopsis thaliana

Endophytic root colonisation of the host plant Arabidopsis thaliana by the beneficial root endophyte Serendipita indica is characterised by an initial biotrophic phase followed by a restricted host cell death-associated phase. During colonisation two secreted S. indica effectors synergistically produce the cell death inducer deoxyadenosine (dAdo). Although the mechanism of regulated cell death is important for fungal accommodation, the host molecular pathways that restrict S. indica -induced cell death and allow the maintenance of a mutualistic relationship are largely unknown. Here we show that autophagy, a major degradation pathway plays a key role in the beneficial interaction between S. indica and Arabidopsis. Autophagy restricts fungal colonisation and exerts a protective function against dAdo-induced cell death. Impairment of dAdo uptake in an autophagy mutant background confers resistance to dAdo-induced cell death and precludes the symbiosis-mediated cell death. Taken together, we propose that autophagy-driven pro-survival responses are required to facilitate a long-lasting mutualistic interaction between S. indica and Arabidopsis. ### Competing Interest Statement The authors have declared no competing interest.