Expression analysis of genes related to cold tolerance in Dendroctonus valens

Abstract

Pine beetles are well known in North America for their widespread devastation of pine forests. However, Dendroctonus valens LeConte is an important invasive forest pest in China also. Adults and larvae of this bark beetle mainly winter at the trunks and roots of Pinus tabuliformis and Pinus sylvestris; larvae, in particular, result in pine weakness or even death. Since the species was introduced from the United States to Shanxi in 1998, its distribution has spread northward. In 2017, it invaded a large area at the junction of Liaoning, Inner Mongolia and Hebei provinces, showing strong cold tolerance. To identify genes relevant to cold tolerance and the process of overwintering, we sequenced the transcriptomes of wintering and non-wintering adult and larval D. valens using the Illumina HiSeq platform. Differential expression analysis methods for other non-model organisms were used to compare transcript abundances in adults and larvae at two time periods, followed by the identification of functions and metabolic pathways related to genes associated with cold tolerance. We detected 4,387 and 6,091 differentially expressed genes (DEGs) between sampling dates in larvae and adults, respectively, and 1,140 common DEGs, including genes encoding protein phosphatase, very long-chain fatty acids protein, cytochrome P450, and putative leucine-rich repeat-containing proteins. In a Gene Ontology (GO) enrichment analysis, 1,140 genes were assigned to 44 terms, with significant enrichment for cellulase activity, hydrolase activity, and carbohydrate metabolism. Kyoto Encyclopedia of Genes and Genomes (KEGG) classification and enrichment analyses showed that the lysosomal and purine metabolism pathways involved the most DEGs, the highly enriched terms included autophagy—animal, pentose and glucuronate interconversions and lysosomal processes. We identified 140 candidate genes associated with cold tolerance, including genes with established roles in this trait (e.g., genes encoding trehalose transporter, fructose-1,6-bisphosphatase, and trehalase). Our comparative transcriptome analysis of adult and larval D. valens in different conditions provides basic data for the discovery of key genes and molecular mechanisms underlying cold tolerance.

Support for the adaptive decoupling hypothesis from whole‐transcriptome profiles of a hypermetamorphic and sexually dimorphic insect, Neodiprion lecontei

“…First, only the adults were exposed to extended cold exposure (2–20 days) prior to tissue collection. Importantly, cold exposure can induce changes in gene expression in insects (see Freda et al, 2017; Zhao et al, 2021 and references therein). We note, however, that the 4℃ storage that we used was more moderate than most experiments (typically 0℃) that have investigated the impact of cold stress or chill‐comas on gene expression.…”

“…Importantly, N. lecontei adults recover from the 4℃ chill-coma within minutes and immediately resume normal mating and host-seeking behaviours. Although adults are likely to encounter low temperatures in the field, it is nevertheless possible that cold storage could contribute to differences in gene expression between adults and larvae (Freda et al, 2017;Pujol-Lereis et al, 2014;Zhao et al, 2021). To reduce this effect, we warmed adults to room temperature (22℃) and enclosed them in a mesh cage containing Pinus seedlings for a minimum of 15 min to ensure that they exhibited normal host-and mate-seeking behaviour.…”

Transcriptome Analysis for Identification of Genes Related to Growth and Development, Digestion and Detoxification, Olfaction in the Litchi Stink Bug Tessaratoma papillosa

“…Transcriptome sequencing technology plays a vital role in non-model insect gene discovery and gene function studies. The technology has enabled various species ( Bayega et al, 2021 ; Zhan et al, 2021 ; Zhao et al, 2021 ). We performed transcriptome and RNA-SEQ sequencing on the T. papillosa genome at different developmental stages and different tissues.…”

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

“…In September, RTBs overwinter as mature larvae, adults, even pupae, 2nd-or 3rd-instar larvae [16]. In recent years, alongside the distribution of pine forest, RTB has spread to more northern regions of China, such as Liaoning province and the Inner Mongolia Autonomous Region [17][18][19]. Due to the severity of the RTB outbreak in China, various aspects of the invasion dynamics of this insect have been studied [14], including its ecology [20] and yeast associates [15], the bioactivities of microorganisms against host defensive monoterpenes [21], the survival of RTB and its adaptability to a climate warming scenario [22], and the diversity of fungi associated with the insect [23][24][25].…”

“…In our previous study, we found that glycerol, trehalose, and sorbitol may help RTB larvae to survive during overwintering [29]. Recently, Zhao et al [19] compared the transcriptomes of wintering and non-wintering adult and larval D. valens, then identified a series of genes associated with cold tolerance. Another factor limiting the supercooling ability of insects is the existing of nucleating agents catalyzing ice formation at high subzero temperatures [30].…”