ABSTRACT
Drosophila male courtship is controlled by the male-specific products of the fruitless (fruM gene and its expressing neuronal circuitry. fruM is considered a master gene that controls all aspects of male courtship. By temporally and spatially manipulating fruM expression, we found that fruM is required during a critical developmental period for innate courtship towards females, and its function during adulthood is relatively trivial. By altering or eliminating fruM expression, we generated males that are innately heterosexual, homosexual, bisexual, or without innate courtship but could acquire such behavior in an experience-dependent manner. These findings show that fruM is not absolutely necessary for courtship but is critical during development to build a sex circuitry with reduced flexibility and enhanced efficiency and provide a new view about how fruM tunes functional flexibility of a sex circuitry.
