The First Report on the Transovarial Transmission of Microsporidian Nosema bombycis in Lepidopteran Crop Pests Spodoptera litura and Helicoverpa armigera.

Zeyang Zhou,Dan Xia,Bin Yu,Boyan Pei,Tian Li,Chunxia Wang

doi:10.3390/microorganisms9071442

Zeyang Zhou, Dan Xia + Show 4 more

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https://doi.org/10.3390/microorganisms9071442

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Journal: Microorganisms	Publication Date: Jul 3, 2021
Citations: 9	License type: CC BY 4.0

Affiliation: Southwest University, Chongqing Normal University

Abstract

Microsporidia are ubiquitous fungi-related parasites infecting nearly all vertebrates and invertebrates. Microsporidian Nosema bombycis is a natural pathogen of multiple insects, including the silkworm and many agricultural and forest pests. N. bombycis can transovarially transmit in silkworm and cause huge economic losses to the sericulture. However, it remains unclear whether N. bombycis vertically transmits in the crop pests Spodoptera litura and Helicoverpa armigera. Here, we investigated the infection of N. bombycis in S. litura and H. armigera to illuminate its infectivity and transovarial transmission. In result, tissue examination with light microscopy revealed that the fat body, midgut, malpighian tubules, hemolymph, testis, and ovary were all infected in both pest pupae. Immunohistochemical analysis (IHA) of the ovariole showed that a large number of parasites in maturation and proliferation presented in follicle cell, nurse cell, and oocyte, suggesting that N. bombycis can infect and multiply in these cells and probably transovarially transmit to the next generations in both pests. Microscopic examination on the egg infection rate demonstrated that 50% and 38% of the S. litura and H. armigera eggs were congenitally infected, respectively. IHA of both eggs manifested numerous spores and proliferative pathogens in the oocyte, confirming that N. bombycis can invade into the female germ cell from the parent body. After hatching of the infected eggs, we detected the infection in offspring larvae and found large quantities of proliferative pathogens, confirming that N. bombycis can transovarially transmit in S. litura and H. armigera, and probably persists in both pest populations via congenital infection. In summary, our work, for the first time, proved that N. bombycis is able to vertically transmit in S. litura and H. armigera via infecting the oocyte in the parent, suggesting that N. bombycis could be a biological insecticide for controlling the population of crop pests.

Highlights

Microsporidia are a group of obligate intracellular parasites that infect most vertebrates and invertebrates and are composed of over 200 genera and 1400 species [1]
Microsporidia have been found widely prevalent in insects, mammals, birds, and water [2,3]
N. bombycis bombycis infection infection and and transmission transmissionhave havebeen beenwell wellcharacterized characterizedininsilkworm, silkworm, but little is known about its infection in crop pests

Summary

Introduction

Microsporidia are a group of obligate intracellular parasites that infect most vertebrates and invertebrates and are composed of over 200 genera and 1400 species [1]. Microsporidia have been found widely prevalent in insects, mammals, birds, and water [2,3]. Microsporidia cause human microsporidiosis [1,4] and lead to huge economic losses by infecting economically important animals, such as silkworm, bee, shrimp, crab, and fish [5,6]. Nosema bombycis is the first identified microsporidia and causes silkworm pébrine disease. N. bombycis can horizontally and vertically transmit in silkworm [7] and is one of the biggest threats to sericulture [8].

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