First moisture-sensing genes identified

November 14th, 2007 - 10:16 am ICT by admin  
Researchers in the University of Iowa Roy J. and Lucille A. Carver College of Medicine have identified the first two genes involved in moisture sensing (hygrosensation).

The finding has also uncovered a “two-sensor” hygrosensing system in fruit flies that may allow the flies to spot delicate changes in humidity, an ability that is key to the flies’ survival.

Slight changes in humidity affect reproductive behaviour and geographic distribution in many animals, including insects, reptiles and birds. Because of their small size, insects, specifically, require a delicately tuned ability to detect moisture levels in their environment in order to survive.

However, the mechanisms and molecules involved in moisture sensing have remained unknown so far.

“Moisture sensing is a sensory modality, which up to this point no one has understood. This is the first study to identify genes that are involved,” Nature quoted Lei Liu, Ph.D., UI postdoctoral fellow in internal medicine and lead author of the study, as saying.

Liu and colleagues made their breakthrough by testing the idea that moisture sensing is a special form of mechanosensation, the ability to spot physical forces like touch or movement.

The team put various genetic techniques into use to study over 20 genes assumed to be involved in touch in fruit flies. After screening each gene mutation for its effect on the flies’ ability to detect moisture, the researchers spotted two genes that are required for normal moisture sensing.

Additionally, they found that one of the genes, “nanchung,” is involved in detecting dry air, while the other gene, “water witch,” is required for detecting moist air.

Both genes are members of the transient receptor potential (TRP) family of genes that code for ion channels. Nanchung, which means “can’t hear” in Korean, has previously been shown to be involved in hearing. Water witch has no other known function and was named by Liu and colleagues for its role in sensing moist air. Interference of either gene impaired the flies’ hygrosensing ability, the researchers said.

The researchers also examined the location the two genes are expressed in the fruit flies and found that not only are two separate genes involved in hygrosensation, but also two types of neurons.

“This work provides the first evidence for a sensory system coded by two types of sensory neurons, one responsible for detecting increased moisture and the other responsible for detecting decreased moisture,” Liu said.

The researchers believe that this two-sensor system may permit the flies to detect relative humidity with great sensitivity.

Liu added that the “two-sensor” system might also be a model for other sensory processes where the ability to detect subtle environmental changes is important, such as temperature sensing.

The study is published in the Nov. 8 issue of Nature. (ANI)

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