Fig. 2. A) The two-choice oviposition assay. (B) Oviposition preferences of D. suzukii and D. melanogaster for ripe and overripe strawberry. 

Compared to most closely related species, including the commonly used model organism D. melanogaster, which lay eggs on fermented fruit, spotted wing Drosophila (SWD) (also known as D. suzukii) lay eggs on ripe fruit (Fig. 1). 

This evolutionary shift poses not only an urgent agricultural problem, but also a fascinating biological problem.  What are the mechanisms underlying such a shift? 

The shift in egg-laying preference requires changes in the sensation of many sensory stimuli, including chemosensory. Our previous work, supported by LSRF and NIH, demonstrated at the behavioral, cellular, and molecular levels that D. suzukii and D. melanogaster sense bitter compounds and sugars differently  (Dweck et al., 2021; Wang, Dweck et al., 2022).  This work invites a similar comparison of the sensation of other significant chemosensory cues. 

Fig. 3. Log2 Fold change plot highlighting differentially expressed chemosensory-related genes between D. suzukii and D. melanogaster (| log2FC| ≥ 2, q < 0.01).

Our preliminary results  (Dweck et al., 2021; Wang, Dweck et al., 2022) have already generated several intriguing hypotheses  (Fig. 2) as to the cellular and molecular mechanisms underlying the oviposition shift of SWD. 

We will test these hypotheses either by misexpression of receptors in D. melanogaster or by CRISPR-Cas9-generated mutation of receptor genes in D. suzukii.  

Fig. 4. Measuring the response of neurons to odors/tastants using electrophysiology

We will use the state-of-art-technology in electrophysiology to test the role of candidate genes in the cellular changes underlying the transition of SWD to lay on egg ripe fruit (Figure 4). 

Fig.5. Our arsenal of behavioral assays

Using an arsenal of behavioral assays, we will test the role of candidate genes in SWD egg-laying shift (Figure 5).