Investigating the microbial community of Cacopsylla spp. as potential factor in vector competence of phytoplasma

Abstract

Phytoplasmas are obligatory intracellular bacteria that colonize the phloem of many plant species and cause hundreds of plant diseases worldwide. In nature, phytoplasmas are primarily transmitted by hemipteran vectors. While all phloem‐feeding insects could in principle transmit phytoplasmas, only a limited number of species have been confirmed as vectors. Knowledge about factors that might determine the vector capacity is currently scarce. Here, we characterized the microbiomes of vector and non‐vector species of apple proliferation (AP) phytoplasma ‘Candidatus Phytoplasma mali’ to investigate their potential role in the vector capacity of the host. We performed high‐throughput 16S rRNA metabarcoding of the two principal AP‐vectors Cacopsylla picta and Cacopsylla melanoneura and eight Cacopsylla species, which are not AP‐vectors but co‐occur in apple orchards. The microbiomes of all species are dominated by Carsonella, the primary endosymbiont of psyllids and a second uncharacterized Enterobacteriaceae endosymbiont. Each Cacopsylla species harboured a species‐specific phylotype of both symbionts. Moreover, we investigated differences between the microbiomes of AP‐vector versus non‐vector species and identified the predominant endosymbionts but also Wolbachia and several minor taxa as potential indicator species. Our study highlights the importance of considering the microbiome in future investigations of potential factors influencing host vector competence. We investigated the potential role of symbiotic bacteria in the acquisition and transmission of phytoplasma. By comparing the two main psyillid vector species of Apple proliferation (AP) phytoplasma and eight co‐occurring species, which are not able to vector AP‐phytoplasma, we found differences in the microbial communities of AP‐vector and non‐vector species, which appear to be driven by the predominant symbionts in both vector species and Wolbachia and several minor taxa in the non‐vector species. In contrast, infection with AP‐phytoplasma did not affect microbiome composition in both vector species. Our study provides new insights into the endosymbiont diversity of Cacopsylla spp. and highlights the importance of considering the microbiome when investigating potential factors influencing host vector competence.

Microbiome of pear psyllids: A tale about closely related species sharing their endosymbionts

“…A maximum likelihood phylogenetic analysis of these ASVs and 16S rRNA sequences from other psyllid‐associated endosymbionts showed that Group 1 pyri and Group 1 pyricola formed a strongly supported clade together with the endosymbiont of Cacopsylla jukyungi (BS = 97), which was well‐supported as a sister clade to the endosymbionts of C. myrthi and Anomoneura mori (BS = 100) (Figure 3B ). Likewise, the close relationship with Enterobacteriaceae endosymbionts in C. myrthi and A. mori had been observed also in other Cacopsylla species (Morrow et al, 2020 ; Schuler et al, 2022 ), suggesting that these ASVs represent an endosymbiont clade widespread in the subfamily of Psyllinae (Psyllidae). In contrast, the most abundant ASVs assigned to Enterobacteriaceae in C. pyrisuga were referred to as “Group2 pyrisuga ” in our study (87.56% of all reads from C. pyrisuga ).…”

“…These endosymbionts were recovered at a very high relative abundance and were identified as unclassified Enterobacteriaceae that are not yet formally described. Similarly, Morrow et al (2017Morrow et al ( , 2020, Kwak et al (2021), Nakabachi et al (2022) and Schuler et al, 2022 found endosymbionts referred to as unclassified Enterobacteriaceae in several Cacopsylla species. Altogether, unclassified Enterobacteriaceae were detected in six out of seven currently recognized psyllid families (cf.…”

“…However, because our results on the phylogenetic relationships of Enterobacteriaceae endosymbionts of the studied Cacopsylla species were based on short fragments of the 16S rRNA gene, this should be interpreted with caution. Considering the occurrence of Enterobacteriaceae endosymbionts at high abundance in all analysed psyllid specimens as well as in other psyllid taxa (e.g., Kwak et al, 2021;Morrow et al, 2017Morrow et al, , 2020Nakabachi et al, 2022;Overholt et al, 2015;Schuler et al, 2022), their presence throughout the entire psyllid life cycle and relatedness to the endosymbionts of C. myrthi and A. mori, which are known to be localized in the bacteriome together with Carsonella, it is likely that the Enterobacteriaceae endosymbionts recovered from C. pyri, C. pyricola and C. pyrisuga are vertically transmitted, obligate co-primary (CP-) endosymbionts. However, to validate our hypothesis, the metabolic potential and tissular localization of the Enterobacteriaceae endosymbionts still need to be elucidated.…”

“…Its broad range of symbiotic relationships encompasses both beneficial and manipulative associations (Ferree et al, 2008;Gherna et al, 1991;Hansen et al, 2007;McCutcheon et al, 2019;Nov akov a et al, 2009;Šochov a et al, 2017). While Arsenophonus was previously detected in various psyllid species (Hall et al, 2016;Morrow et al, 2017;Nakabachi et al, 2022;Schuler et al, 2022;Sloan & Moran, 2012;Subandiyah et al, 2000;Thao et al, 2000), potentially as an obligate or at least beneficial symbiont (Hall et al, 2016;Hansen et al, 2007;Morrow et al, 2017;Subandiyah et al, 2000), its role in C. pyrisuga, particularly in remigrants that could transmit phytoplasma, remains to be elucidated.…”

Multiple factors driving the acquisition efficiency of apple proliferation phytoplasma in Cacopsylla melanoneura

“…The opposite was true for the non-infected individuals of C. picta, which harbored a lower number of bacterial taxa compared to the infected individuals. Psyllids with a high phytoplasma concentration had more divergent microbiomes and, most importantly, there was a signi cant difference between the microbiomes of C. melanoneura, C. picta and eight non-AP transmitting Cacopsylla species, highlighting the potential role of the microbiome in the acquisition and transmission of phytoplasmas (Schuler et al 2022). Therefore, further studies should be performed on the microbiome of C. melanoneura from NW and its potential interaction with 'Ca.…”