Extremely distinct microbial communities in closely related leafhopper subfamilies: Typhlocybinae and Eurymelinae...

Among the Hemiptera insects, a widespread way of feeding is sucking sap from host plants. Due to their nutrient-poor diet, these insects enter into obligate symbiosis with their microorganisms involved in the synthesis of components essential for host survival. However, within the Cicadellidae family, there is a relatively large group of mesophyll feeders-Typhlocybinae-that is considered to be devoid of obligate symbiotic companions. In this work, we examine the composition of microorganisms in this subfamily and compare the results with their close relatives-the Eurymelinae subfamily. To study the microbiome, we used high-throughput next-generation sequencing (NGS, Illumina) and advanced microscopic techniques, such as transmission electron microscopy (TEM) and fluorescence in situ hybridization (FISH), in a confocal microscope. In the bodies of Typhlocybinae insects, we did not detect the presence of microorganisms deemed to be obligate symbionts. Their microbial communities consist of facultative symbionts, mainly alphaproteobacteria such as Wolbachia or Rickettsia as well as others that can be considered as facultative, including Spiroplasma, Acidocella, Arsenophonus, Sodalis, Lariskella, Serratia, Cardinium, and Asaia. On the other hand, the Eurymelinae group is characterized by a high diversity of microbial communities, both obligate and facultative, similar to other Cicadomorpha. We find co-symbionts involved in the synthesis of essential amino acids such as Karelsulcia, betaproteobacteria Nasuia, or gammaproteobacteria Sodalis. In other representatives, we observed symbiotic yeast-like fungi from the family Ophiocordycipitaceae or Arsenophonus bacteria inhabiting the interior of Karelsulcia bacteria. Additionally, we investigated some aspects of symbiont transmission and the phylogeny of symbiotic organisms and their hosts.

The Typhlocybinae and Eurymelinae leafhoppers differ significantly in their symbiotic communities. They have different diets, as Typhlocybinae insects feed on parenchyma, which is richer in nutrients, while Eurymelinae, like most representatives of Auchenorrhyncha, consume sap from the phloem fibers of plants. Our work presents comprehensive studies of 42 species belonging to the two above-mentioned, and so far poorly known, Cicadomorpha subfamilies. Phylogenetic studies indicate that the insects from the studied groups have a common ancestor. The diet shift in the Typhlocybinae leafhoppers contributed to major changes in the composition of microorganisms inhabiting the body of these insects. Research on the impact of diet on the microbiome and the subsequent consequences on the evolution and adaptation of organisms plays an important role in the era of climate change.