Autophagy participates in innate immune defense in lamprey

Autophagy is a homeostatic process which degrades cytoplasmic constituents to maintain the balance of organs when they were challenged with nutrient stress. It also participates in cancer, neurodegenerative disorders, aging and innate immune defense. In order to reveal how autophagy participates in innate immune response when invertebrates evolved into vertebrates. Firstly, we performed a systematic analysis of Atg genes and found that they are highly conserved among lancelet, lamprey and zebrafish. Then, we observed autophagosomes upon starvation by TEM in lancelet, lamprey and zebrafish and found that the morphology of autophagosome is similar to that was observed in yeast and mammals. In addition, rapamycin can induce autophagy in lamprey leukocytes and the deficiency of human Beclin1 protein can be rescued by lancelet and lamprey Beclin1 proteins. When lamprey leukocytes were treated with polyI:C and LPS, autophagy was induced. Moreover, when lamprey leukocytes were challenged with live E. coli, phagocytosis along with autophagy was triggered to degrade pathogenic bacteria. In all, our study here indicated that autophagy is highly conserved during evolution and plays a key role in innate defense when invertebrates evolved into vertebrates. •The morphology of autophagosomes in lancelet and lamprey are identical with those found in other species.•Several conserved Atg genes are present in lancelet and lamprey.•Starvation, rapamycin, polyI:C, LPS and E. coli all can induce autophagy in single independent cell of lamprey.•Autophagy plays an essential role in innate immune defense in lamprey leukocytes.