Beauveria bassiana Ribotoxin (BbRib) Induces Silkworm Cell Apoptosis via Activating Ros Stress Response

Abstract

The BbRib gene participates in the infection process of Beauveria bassiana (B. bassiana). It also helps pathogenic fungi to escape and defeat the insect host immune defense system by regulating the innate immune response. However, model insects are rarely used to study the mechanism of fungal ribosomal toxin protein. In this study, BbRib protein was produced by prokaryotic expression and injected into silkworm (Bombyx mori) larvae. The physiological and biochemical indexes of silkworm were monitored, and the pathological effects of BbRib protein on immune tissues of silkworm were examined by Hematoxylin and Eosin (HE) staining. BbRib protein can significantly affect the growth and development of the silkworm, causing poisoning, destroying the midgut and fat body and producing physiological changes. The ROS stress response in the adipose tissue and cells of the silkworm was activated to induce apoptosis. These results indicated that the BbRib gene not only participates in the infection process of B. bassiana, it also helps the pathogenic fungi escape the immune system by regulating the innate immune system of the silkworm, allowing it to break through the silkworm’s immune defense. This study reveals the potential molecular mechanism of BbRib protein to insect toxicity, and provides a theoretical basis and material basis for the development and use of novel insecticidal toxins.