Transovarial Transmission of Bacteriome-Associated Symbionts in the Cicada Pycna repanda (Hemiptera: Cicadidae)

Abstract

Although transovarial transmission of bacteriome-associated symbionts in hemipteran insects is extremely important for maintaining intimate host-symbiont associations, our knowledge of cellular mechanisms underlying the transmission process is quite limited. We investigated bacterial communities of salivary glands, bacteriomes, and digestive and reproductive organs and clarified the transovarial transmission of bacteriome-associated symbionts of the mountain-habitat specialist Pycna repanda using integrated methods. The bacterial communities among different gut tissues and those of bacteriomes of males and females both show similarity, whereas differences are exhibited among bacterial communities in testes and ovaries. The primary symbionts “Candidatus Sulcia muelleri” (hereafter “Ca. Sulcia”) and “Candidatus Hodgkinia cicadicola” (hereafter “Ca. Hodgkinia”) were not only restricted to but also dominant in the bacteriomes and ovaries. “Ca. Hodgkinia” cells in the bacteriomes of both sexes exhibited different colors by histological and electron microscopy. Also considering the results of a restriction fragment length polymorphism (RFLP)-based cloning approach, we hypothesize that “Ca. Hodgkinia” may have split into cytologically different cellular lineages within this cicada species. Regarding the dominant secondary symbionts, Rickettsia was detected in the salivary glands, digestive organs, and testes, whereas Arsenophonus was detected in the bacteriomes and ovaries. Our results show that Arsenophonus can coexist with “Ca. Sulcia” and “Ca. Hodgkinia” within bacteriomes and can be transovarially transmitted with these obligate symbionts together from mother to offspring in cicadas, but it is not harbored in the cytoplasm of “Ca. Sulcia.” The change in the shape of “Ca. Sulcia” and “Ca. Hodgkinia” during the transovarial transmission process is hypothesized to be related to the limited space and novel microenvironment. IMPORTANCE Cicadas establish an intimate symbiosis with microorganisms to obtain essential nutrients that are extremely deficient in host plant sap. Previous studies on bacterial communities of cicadas mainly focused on a few widely distributed species, but knowledge about mountain-habitat species is quite poor. We initially revealed the physical distribution of the primary symbionts “Ca. Sulcia” and “Ca. Hodgkinia” and the dominant secondary symbionts Rickettsia and Arsenophonus in the mountain-habitat specialist Pycna repanda and then clarified the transovarial transmission process of bacteriome-associated symbionts in this species. Our observations suggest that “Ca. Hodgkinia” may have split into cytologically distinct lineages within this cicada species, and related cicadas might have developed complex mechanisms for the vertical transmission of the bacteriome-associated symbionts. We also revealed that Arsenophonus can be transovarially transmitted in auchenorrhynchan insects when it is not harbored in the cytoplasm of other endosymbionts. Our results highlight transovarial transmission mechanisms of bacteriome-associated symbionts in sap-feeding insects.

Structural diversity of symbionts and related cellular mechanisms underlying vertical symbiont transmission in cicadas

“…Besides the obligate symbionts, some facultative symbionts, such as Rickettsia , Arsenophonus , Wolbachia , Sodalis and Spiroplasma , were also detected from some cicada species in our present study and some previous studies (e.g., Matsuura et al ., 2018; Huang et al ., 2020). These facultative symbionts can be harboured in either the fat bodies (e.g., Rickettsia in Platyp.…”

“…kaempferi ) or the bacteriomes (e.g., Arsenophonus in Py. repanda ) (Huang et al ., 2020), or in both (Supporting Information Table S2). To date, secondary symbionts have been reported to be often involved in reproductive manipulations, host plant utilization, and the ability to cope with environmental factors (e.g., the response to heat stress and chemical insecticides) (Oliver et al ., 2003; Kontsedalov et al ., 2008).…”

The diversity and function of intestinal microorganisms in four geographic Cephalcia chuxiongica (a pine defoliator) populations

“…The similar environmental factors due to close geographic distance (Table S2) may result in a similar symbiotic microbiota in insects, and vice versa (Liu et al, 2020). Moreover, the structure of resident microbiota can be affected by host genotype (Chaston et al, 2016;Fan et al, 2020;Garcia-Lozano et al, 2020) and vertically transmission of microbiota from parents to offspring (Campbell et al, 2012;Huang et al, 2020;Michaud et al, 2020). C. chuxiongica does not migrate long distances and thus their expanding should be a gradual process.…”

“…In Drosophila, studies also indicated that the composition and abundance of the resident microbiota can be influenced by host genotype, which contributes to the genotype-phenotype relationship of the host (Chaston et al, 2016;Garcia-Lozano et al, 2020). Secondly, the primary symbionts can also be transmissed vertically from parents to offspring in insects (Huang et al, 2020;Michaud et al, 2020), and thus, it is possible that the composition of microbiota may correlate with host population genetics. In the wood-feeding termite R. grassei, a vertical transmission of symbiont (from parents to offspring) test revealed that transmission rates were high, with an average of 0.897 per protist species; both the queen and the king contributed to the gut microbiota of the offspring (Michaud et al, 2020).…”

The Biocontrol and Plant Growth-Promoting Properties of Streptomyces alfalfae XN-04 Revealed by Functional and Genomic Analysis

“…Plasmid pIJ8641 was transformed into the donor strain E. coli ET12567 (pUZ8002) and then conjugated into recipient XN-04 as previously described ( Kieser et al, 2000 ; Zhang et al, 2021 ). Genomic DNA of wild-type (WT-) and transformed (t-) XN-04 was extracted, and the quality was tested by primers 27F (5′-AGAGT TTGAT CCTGG CTCAG-3′) and 1492R (5′-GGTTA CCTTG TTACG ACTT-3′; Huang et al, 2020 ). The EGFP gene was detected in the t-XN-04 strain following the protocol described before ( Bonaldi et al, 2015 ) and the expression was observed by Confocal Laser Scanning Microscope (CLSM; Olympus model FV3000, Japan).…”