The Functional Analyses Of The Woronin Body In Arthrobotrys Oligospora

Arthrobotrys oligospora is the model fungus to study the interaction between nematode-trapping fungi and nematodes. It captures nematodes by adhesive nets (three-dimensional nets).3D-traps are not only the weapon of capturing nematodes and the foundation of its bio-control, but also the key indicator of the nematophagous fungi switching from saprophytic to predacious lifestyles. The Woronin body is a unique organelle present in Pezizomycotina species. During the injury of hyphae, Woronin bodies can quickly close the septal pores to reduce the loss of cytoplasm and help hyphae healing. During normal growth of hyphae, Woronin bodies perform the ability to occlude septal pores and to thereby control the cell-to-cell transport, and this is crucial for filamentous fungi growth and hyphal differentiation Woronin body is also considered as a significant element for efficient pathogenesis of many fungal pathogens. It plays a direct role in the asexual reproduction, development of infection structure and survival under hostile environment. In this study, we analyzed the function of Woronin body in A. oligospora based on the gene knockout technology.The main findings of this study were described as follows:1. Gene knockout studies of AoHexKnockout vector of the AoHex gene was constructed via electro-transformation of Saccharomyces cerevisiae and Escherichia coli competent cells of the recombinant arms, the hygromycin resistance gene and the linearized plasmid pRS426for in vivo homologous recombination. CaCl2-PEG mediated transformation method was used to transform the A. oligospora protoplast, and positive transformants were screened by PCR and confirmed by Southern blot methods.2. Phenotypes and physiological features analysis of the wild and mutant strainsThe physiological and biochemical characteristics of the wild type strains and mutants were compared, including Woronin body genesis in hypha, growth rate, colonial morphology, sporulation, spore morphology and trapping-device formation. The results showed that the growth rate and sporulation of AoHex mutants were decreased. The fungus can not form three-dimensional nets and captures nematodes. Moreover, the transmission electron microscope (TEM) analysis showed that the dense Woronin bodies cannot observed in either side of the septum of the mutant strain. These studies indicate that Woronin body plays an important role in the hyphal growth, sporulation and3D-traps formation.The novelties of this study were described as follows:1. The gene AoHex of A. oligospora, which involved in Woronin body formation, were deleted, and hyphae ultrastructural morphology of A. oligospora and AoHex deletion mutant strains were observed by TEM.2. The physiological and biochemical characteristics of the wild type strains and AoHex deletion mutants were systematically compared. Our results confirmed that in A. oligospora, AoHex protein is essential for Woronin body formation and function, and Woronin body plays a direct role in hyphae growth, the asexual reproduction and the formation of3D-traps.