Leader: Ewald Grosse-Wilde
Here we focus on the bark beetle itself. The goal is to find new ways to intervene in the mass devastation
During our initial years we have sequenced and analysed the genome of our main species of interest,
Task G1a: Genomes of several bark beetle species, including the Eurasian spruce bark beetle Ips typographus
Task leader: Ewald Grosse-Wilde
Powell D, Große-Wilde E, Krokene P, Roy A, Chakraborty A, Löfstedt C, Vogel H, Andersson MN, Schlyter F. 2021. A highly contiguous genome assembly of a major forest pest, the Eurasian spruce bark beetle Ips typographus. Communications Biology 4: 1059. 10.1038/s42003-021-02602-3
Task G1b:De-orphanisation of bark beetle Olfactory Receptors
Task leader: Dr. Blanka Kalinova
The olfactory system mediates detection of odours in the environment and has direct influence on host plant selection. We use the genome and other sources on gene content of the beetle to identify so called Olfactory Receptors (ORs). Insect ORs are generally used in insects to identify chemical cues, and especially in the detection of volatile, long-distance pheromones and plant compounds. In close collaboration with our partners in EXTEMIT-K we will try to identify specific ORs in the bark beetle as new targets for intervention. A long-term goal is to find compounds that block such receptors, which would essentially negate the pheromone and severely reduce mass attacks. The first step, in which the correct receptors are identified (De-orphanisation), is done by manipulating vinegar flies (Drosophila melanogaster) to express beetle receptors. Here we make use of the so-called Empty Neuron System (ENS) that was originally established by Hallem and Carlsson (2004) (Figure at right). Flies will express the bark beetle receptor genes in specific neurons on their antennae that lack a fly OR. The flies can then be tested in electrophysiological experiments, directly measuring the activity of the neuron when stimulated with odours in so called Single Sensillum Recordings (SSR, below). If the receptor is a pheromone receptor, the neuron will respond to bark beetle pheromone. This approach has been used many Diptera and a few Lepidoptera (de Fouchier et al., 2016), we attempt the first in Coleoptera on large scale by ENS method (Empty Neuron System).
Task G1: Progress and Outlook
Our high-quality genome database by sequencing DNA by Pac Bio from highly inbred beetle strains is published (Powell et al. 2021). This dataset will not only be used to support EXTEMIT-K work but is also publicly available, prepared to be useful for other scientists working with Ips species and other bark beetles.
Beyond serving as a foundation for the other projects in G-level, we are currently working on expanding genome sequencing efforts to other Ips species with different host profiles, in an effort to see which genes/gene families are primarily affected by this lifestyle change. This project is the basis of several collaborations, and also includes members of G2.
The well-staffed rearing facility for dew flies (Drosophila melanogaster) and a pipeline for the generation of fly line that express bark beetle receptors in their antennae to allow for functional analysis of the receptors proteins in a controlled environment, using single sensillum recordings (G1b). This will allow us to associate receptors with the detection of specific odorants of importance in the context of mass attacks on spruce forests.
Additionally, we can combine the physiological tests with gas chromatography (GC) to identify new, specialized receptors that detect so far unknown compounds that might be important for the beetle (Figure at right). This allows us to test many volatile compounds from sources of material potentially bad for the beetle, like old, colonised bark, and determine which compound (GC) activates which receptor in a sensillum (SSR). Using this approach, we can find novel compounds that are of ecological relevance to the beetle, and directly associate them with the responding OR.
De-orphanisation & GC-SSR-ENS: (Gas Chromatography – Single Sensilllum Recording – Empty Neuron System): Allows analysis by stimulation of single compound from complex samples directly to defined ORs.
Task G2: Progress and Outlook
At present, we are carrying out gene expression studies and microbial studies further to enhance our understanding
Recently, we have identified reference genes in Ips typographus (Sellamuthu et al 2021), to facilitate ongoing
The goal is to find new intervention targets, but also to couple the beetle response to findings from T-level
A new avenue added, partly mentioned above, is RNA interference (RNAi) for both research and management.
Reddy M, Mogilicherla K, Smagghe G, Roy A, 2021. RNAi against wood-boring forest pests RNA
For other G-level publications, please see the EXTEMIT-K summary of publications per year