An Overview of Genes From Cyberlindnera americana, a Symbiont Yeast Isolated From the Gut of the Bark Beetle Dendroctonus rhizophagus (Curculionidae: Scolytinae), Involved in the Detoxification Process Using Genome and Transcriptome Data

Abstract

Bark beetles from Dendroctonus genus promote ecological succession and nutrient cycling in coniferous forests. However, they can trigger outbreaks leading to important economic losses in the forest industry. Conifers have evolved resistance mechanisms that can be toxic to insects but at the same time, bark beetles are capable of overcoming tree barriers and colonize these habitats. In this sense, symbiont yeasts present in the gut of bark beetles have been suggested to play a role in the detoxification process of tree defensive chemicals. In the present study, genes related to this process were identified and their response to a terpene highly toxic to bark beetles and their symbionts was analyzed in the Cyberlindnera americana yeast. The genome and transcriptome of C. americana (ChDrAdgY46) isolated from the gut of Dendroctonus rhizophagus were presented. Genome analysis identified 5752 protein-coding genes and diverse gene families associated with the detoxification process. The most abundant belonged to the Aldo-Keto Reductase Superfamily, ATP-binding cassette Superfamily, and the Major Facilitator Superfamily transporters. The transcriptome analysis of non-α-pinene stimulated and α-pinene stimulated yeasts showed a significant expression of genes belonging to these families. The activities demonstrated by the genes identified as Aryl-alcohol dehydrogenase and ABC transporter under (+)-α-pinene suggest that they are responsible, that C. americana is a dominant symbiont that resists high amounts of monoterpenes inside the gut of bark beetles.

Divergence in Gut Bacterial Community Among Life Stages of the Rainbow Stag Beetle Phalacrognathus muelleri (Coleptera: Lucanidae)

“…Many studies have investigated gut microbial species that are critical for the development and survival of the hosts [ 14 , 15 ]. The aim of these studies was to identify how to damage and alter the core microbiota to cause the death of pests, thereby developing new pest control strategies [ 16 , 17 , 18 , 19 ]. Further, gut bacteria in these pests contributed to understand the degrading functions by digesting cellulose and lignin (i.e., wood, litter, and humus) to promote host growth [ 10 , 11 , 12 , 20 , 21 ].…”

Seasonal Shifts in Cold Tolerance and the Composition of the Gut Microbiome of Dendroctonus valens LeConte Occur Concurrently

“…During attack, bark beetles and associated microorganisms must overcome the complex defense system of the tree, which includes toxic monoterpenes, to successfully complete their life cycle. In this process, symbiont yeasts existing in the gut of bark beetles may take part in the detoxification of tree defensive chemicals [78]. For instance, the yeast Cyberlindnera americana (Wickerham) has been detected across different life stages and isolated from the body, ovarioles, and gut (where it is dominant) of Dendroctonus species from several geographical locations [15,79,80].…”

Diversity and Functions of Yeast Communities Associated with Insects

“…Whatever their stage of development, insects may use obligate or facultative yeast symbionts to compensate diverse metabolic functions. Yeasts associated with insects are known to facilitate the host feeding on recalcitrant food [ 82 , 89 , 101 ], provide immunity and protection against various pathogens and parasites [ 47 , 102 ], mediate inter- and intra-specific communication diet [ 103 , 104 ], aid digestion, and supply essential amino acids, metabolic compounds, and nutrients [ 39 , 78 , 105 ]. Those yeasts are essential for the optimal development and survival of many insects, demonstrated by the fact that Drosophila suzukii larvae reared in a yeast-free environment do not reach the pupal stage [ 106 , 107 ].…”

“…For insects feeding on recalcitrant substrate such as wood, yeast symbionts participate to nutrient acquisition and detoxification of defensive plant compounds [ 6 , 73 ]. Some yeasts such as Cyberlindnera americana and Ogataea pini are able to utilize terpenoids as carbon sources, the primary defensive chemicals constitutively present in the phloem resins of conifers, which may be important for Dendroctonus and Ips beetle tolerance of defensive phytotoxins [ 6 , 101 ]. Several structural carbohydrates of host plants (e.g., cellulose, hemicelluloses) are not easily degraded by insects.…”