The Distribution Of Endosymbiotic Bacteria Blochmannia Sp. In Rhabdwscelus Lineaticollis (Heller) And Its Response To The Different Temperature Treatment

Rhabdoscelus lineaticollis is an invasive quarantine pest of palm trees and sugarcane, causing huge economic losses to landscaping, coconut and sugar industry in southern China. The insect harbor numerous intracellular bacteria that have an intimate relationship with the host, promote growth, development, and reproduction. However, no studies have been conducted to explore the endosymbiotic bacteria of R. lineaticollis in their native or invaded regions. Deciphering the endosymbionts of R. lineaticollis and their physiological functions in situ may provide a theoretical basis to devise a novel biological control strategy against this pest. Here, we explored the endosymbiotic bacteria associated with R. lineaticollis using the methods of molecular biology, obtained the following main findings.1. The diversity of endosymbionts among the laboratory and field population of R. lineaticollis was analyzed using denaturing gradient gel electrophoresis (DGGE) based on 16s rDNA. One band was observed for Blochmannia sp. on DGGE, despite the different environment and food conditions. The total length of the query sequence showed 85% homology with the known Blochmannia sp. using NCBI Blastn database. Meanwhile, amplification of wsp genes by PCR indicated the absence of Wolbachia sp. in R. lineaticollis.2. The relative abundance of Blochmannia sp. across various developmental stages (Eggs, third larvae fifth larvae, ninth larvae, pupae, female and male adult) and temperatures were quantified by qPCR. The results showed that the abundance of Blochmannia sp. was the highest in eggs, followed by male and female adult. While the abundance was the lowest in the larval stage, however, no significant differences were found among the larvae of different ages. Meanwhile, a significant difference was only found between the treatments at 18℃ and 30℃, with the highest abundance at 30℃.3. The tissue distribution of Blochmannia sp. was detected by PCR with gene-specific primer. The results showed that a band was observed in the heads, thorax, abdomen, legs, wings, cuticle, guts, ovaries, and testicles. It was further verified by the blastn search result, after sequencing.In conclusion, we detected Blochmannia sp. in R. lineaticollis, however, no evidence of the presence of Wolbachia was found in this study. The presence of Blochmannia was observed in heads, thorax, abdomen, legs, wings, guts, ovaries and testicles. There were no differences among the different developmental stages but significant difference was found among the different temperatures. These results underlying a relationship between the temperatures and the abundance of Blochmannia sp. which needs further studies to be investigated.