Autophagy is an evolutionarily conserved process that recycles damaged or unwanted cellular components, and has been linked to plant immunity. However, how autophagy contributes to plant immunity is unknown. Here we reported that the plant autophagic machinery targets the virulence factor βC1 of Cotton leaf curl Multan virus (CLCuMuV) for degradation through its interaction with the key autophagy protein ATG8. A V32A mutation in βC1 abolished its interaction with NbATG8f, and virus carrying βC1V32A showed increased symptoms and viral DNA accumulation in plants. Furthermore, silencing of autophagy-related genes ATG5 and ATG7 reduced plant resistance to the DNA viruses CLCuMuV, Tomato yellow leaf curl virus, and Tomato yellow leaf curl China virus, whereas activating autophagy by silencing GAPC genes enhanced plant resistance to viral infection. Thus, autophagy represents a novel anti-pathogenic mechanism that plays an important role in antiviral immunity in plants.DOI: http://dx.doi.org/10.7554/eLife.23897.001

Viruses interfere with and usurp host machinery and circumvent defense responses to create a suitable cellular environment for successful infection. This is usually achieved through interactions between viral proteins and host factors. Geminiviruses are a group of plant-infecting DNA viruses, of which some contain a betasatellite, known as DNAβ. Here, we report that Cotton leaf curl Multan virus (CLCuMuV) uses its sole satellite-encoded protein βC1 to regulate the plant ubiquitination pathway for effective infection. We found that CLCuMu betasatellite (CLCuMuB) βC1 interacts with NbSKP1, and interrupts the interaction of NbSKP1s with NbCUL1. Silencing of either NbSKP1s or NbCUL1 enhances the accumulation of CLCuMuV genomic DNA and results in severe disease symptoms in plants. βC1 impairs the integrity of SCFCOI1 and the stabilization of GAI, a substrate of the SCFSYL1 to hinder responses to jasmonates (JA) and gibberellins (GA). Moreover, JA treatment reduces viral accumulation and symptoms. These results suggest that CLCuMuB βC1 inhibits the ubiquitination function of SCF E3 ligases through interacting with NbSKP1s to enhance CLCuMuV infection and symptom induction in plants.

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