Abstract
Mutual relationships with symbionts play a crucial role in the evolution and ecology of plant-feeding hemipteran insects. However, there was no specific dominant bacterium observed in soft scales (Coccidae) in the previous studies, it is still unclear whether soft scales have specific primary symbionts. In this study, a nuclear ribosomal internal transcribed spacer (ITS)gene fragment was used to analyze the diversity of fungal communities in 28 Coccidae species based on next-generation sequencing (NGS). Furthermore, samples from different developmental stages of Ceroplastes japonicus were sequenced to illustrate the dynamics of fungal community. Our results showed that Coccidae-associated Ophiocordyceps fungi (COF) were prevalent in all 28 tested species with high relative abundance. Meanwhile, the first and second instars of C. japonicus, two important stages for growth and development, had high relative abundance of COF, while the relative abundances in other stages were low, ranging from 0.68% to 2.07%. The result of fluorescent in situ hybridization showed that the COF were widely present in hemolymph and vertically transmitted from mother to offspring. Our study confirms that the COF have intimate associations with the growth and development of soft scales, and provides new evidence to support that COF are primary fungal symbionts for Coccidae.
Highlights
Due to the lack of various essential amino acids in the plant sap, hemipteran insects usually harbor some obligate bacterial symbionts, which provide essential nutrition to complete their diet [1,2]
Ceroplastes rubens, Parasaissetia nigra, Saissetia coffeae, Saissetia oleae, and Coccus hesperidum are well-known polyphagous pests infested on crops and ornamental plants around the world [12]
After merging and quality filtering, 3,608,175 clear tags were selected for further analyses
Summary
Due to the lack of various essential amino acids in the plant sap, hemipteran insects usually harbor some obligate bacterial symbionts, which provide essential nutrition to complete their diet [1,2]. Buchnera in aphids, Sulcia in cicadas, Tremblaya in mealybugs, and Uzinura in armored scale insects have been reported in many studies [3,4,5,6,7,8]. These obligate symbionts own extreme genome reduction including several essential amino acid pathways, and provide amino acids and vitamins for insect hosts [6,9]. Except for the mealybugs and armored scale insects, it has been very ambiguous whether soft scales harbor certain obligate symbionts, which play important roles in growth and development of hosts. The newly hatched nymph of soft scales hunts for the appropriate feeding location and becomes immobile after that
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