Topical Fungal Infection Induces Shifts in the Gut Microbiota Structure of Brown Planthopper, Nilaparvata lugens (Homoptera: Delphacidae)

Abstract

The brown planthopper (Nilaparvata lugens, BPH) is a destructive insect pest posing a serious threat to rice production. The fungal entomopathogen Metarhizium anisopliae is a promising alternative that can be used for BPH biocontrol. Recent studies have highlighted the significant involvement of gut microbiota in the insect–fungus interactions. In the presented study, we investigated the effects of topical fungal infection on the gut microbial community structure in BPH. Our results revealed that topical infection with M. anisopliae increased the bacterial load and altered the bacterial community structure in the gut of BPH. The relative abundances of the dominant gut bacteria at the order, family and genus level were significantly different between fungus-infected and uninfected groups. At the genus level, the uninfected BPH harbored high proportions of Pantoea and Enterobacter in the gut, whereas the fungus-infected BPH gut was absolutely dominated by Acinetobacter. Moreover, topical fungal infection significantly inhibited the expressions of immune-related genes encoding anti-microbial protein and dual oxidase that were involved in the maintenance of gut microbiota homeostasis, indicating that gut bacteria imbalance might be attributed in part to the suppression of gut immunity caused by fungal pathogen. Our results highlighted the importance of the gut microbial community during interactions between fungal pathogens and insect hosts.

Relative contribution of genetic and environmental factors to determination of wing morphs of the brown planthopper Nilaparvata lugens

“…Previous studies showed that crowding at nymph stage of rice planthoppers induced the high proportion of long‐winged adults, and the lower population density of nymphs induce the short‐winged adults (Kisimoto, 1956; Iwanaga et al ., 1985). The short‐winged BPHs were particularly prone to occur on tillering rice, while the long‐winged were easy to develop on yellow ripening rice (Wang et al ., 1997). However, when BPHs had been directly selected for multiple generations, their wing morphs were relatively consistent under different conditions.…”

“…It has been confirmed that the wing morph of rice planthoppers is controlled by multiple genes, and it is also under sex‐limited inheritance (Iwanaga et al ., 1985; Wang et al ., 1997; Peng et al ., 2012). The fact that it needed multigenerational selection to obtain a wing pure‐bred lineage supports the inheritance rule of wing morphs controlled by multiple genes.…”

“…The pure‐bred lineage of a wing morph indicates that wing morphs might be genetically controlled. On the other hand, some studies have been illustrated that the wing morph of insects is dependent on environmental conditions, such as population crowding degree (Kisimoto, 1956; Martínez & Costamagna, 2018), growth stage and nutrition of host plants (Wang et al ., 1997; Lin et al ., 2018), and photoperiod (Fujisaki, 1989; Liu et al ., 2010; Zeng et al ., 2010). These previous studies indicate that genetic backgrounds and environments determine wing morphs of insects.…”

“…Previous studies suggested that the wing morph of the female BPH might be determined by 1 pair of alleles; the allele for the short‐winged morph was dominant and the other for the long‐winged was recessive, and the genetic model of wing morph in females agreed with Mendel's law of segregation whereas the model in males did not agree with this law (Iwanaga et al ., 1985; Yu et al ., 1997). Moreover, Mendel's law of segregation was not found in other studies based on the hybridized experiments between long‐ and short‐winged rice planthoppers (Mori & Nakasuji, 1990; Wang et al ., 1997; Liu et al ., 2010; Peng et al ., 2012). These different results may be attributed to the heterogeneous genetic backgrounds of insects in laboratory cultures.…”

“…Both environmental factors and genes affect the wing morph of the rice planthopper (Mori & Nakasuji, 1990, 1991; Denno et al ., 1991; Wang et al ., 1997; Xu et al ., 2015; Xu & Zhang, 2017; Lin et al ., 2018). Here, we speculated that the homozygote of a wing morph of BPHs might be insensitive to changes in environment factors whereas the heterozygote was sensitive.…”