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As we get older, we may have changing tastes. We can switch from drinking cola to wine, or from eating white chocolate to dark chocolate. According to a new study, the cotton bollworm also experiences such changing tastes, with the larvae and adult forms of the creature having different sugar-sensing systems.
The cotton bollworm, a global pest, causes approximately $3 billion in economic losses to farmers annually. It is often hosted by plants such as tomatoes.
The worm has significantly different eating habits: from the larval stage, in which it eats the leaves, fruits and flower buds of plants, to the adult stage, in which it feasts on the sugar-rich nectar of plants. According to previous studies, the cotton bollworm’s external gustatory sensory neurons (GSNs) – which send taste signals to the brain – are found on the maxillary galea, an area around the mouth in larvae, but the antennae, the tarsi (leg segments furthest from the body), and the proboscis, which has a similar structure to the human tongue, in the adult.
In the current study, researchers compared the behavioral and electrophysiological responses of both adult and larval cotton bollworms to seven different types of sugars found in plants, including glucose, fructose and sucrose.
They found that although both larvae and adults have GSNs that detect sugar, they respond very differently. Larvae are between 100 and 1000 times more sensitive to sucrose than adults. This, the study suggests, could explain why young larvae are attracted to leaves instead of nectar. They can detect sucrose more effectively in areas where it is scarce, such as plant tissue.
In the next phase of the study, researchers analyzed nine sugar taste receptor (GR) genes in the taste organs of the larval and adult cotton bollworm, and tested eight of them for reception of eleven different sugar compounds. Most showed no response, but one, GR10, was specifically tuned to sucrose, and another, GR6, responded to sucrose, fucose, and fructose.
Finally, using CRISPR/Cas9 DNA-modifying techniques, the researchers created two mutant cotton bollworms, one that lacked the function of GR6, and another that lacked the function of GR10. They sought to detect changes in electrophysiological and behavioral responses compared to typical cotton bollworms. From this analysis, the researchers found that GR10 plays a key role in larval preference for sucrose, but GR6 affects the adult cotton bollworm’s detection of sucrose, fucose and fructose.
The research shows that the different ‘tastes’ of cotton bollworms are influenced by the fact that they use different sugar taste receptors to detect different sugar levels. The more sensitive larvae can detect small amounts of sucrose using the GR10, while the less sensitive adult cotton bollworm detects high levels of not only sucrose but also fructose and fucose using the GR6. These findings could help farmers working on pest management initiatives, although the researchers emphasize the need for research on all GRs involved in sugar rushing.
“We reported the molecular basis of sucrose reception in the eternal taste neurons of the cotton bollworm, and found that distinct taste receptors underlie the difference in food selection between the adult and larval stages.,” says Chen-Zhu Wang, one of the authors of the study.
“GRs closely associated with Gr10 and Gr6 are also found in other moth and butterfly species. We therefore speculate that similar sugar sensing mechanisms may also occur in these species, which is worth verifying with future research..”
Sourced from: eLife
‘Sucrose taste receptors differ in larval and adult stages of a moth’
Published on: November 7, 2023
Authors: S. Zhang, P. Wang, C. Ning, K. Yang, G. Li, L. Cao, L. Huang, C. Wang
source : www.foodnavigator.com