fruitlesstunes functional flexibility of courtship circuitry during development

ABSTRACT Drosophila male courtship is controlled by the male-specific products of the fruitless (fru M gene and its expressing neuronal circuitry. fru M is considered a master gene that controls all aspects of male courtship. By temporally and spatially manipulating fru M expression, we found that fru M is required during a critical developmental period for innate courtship towards females, and its function during adulthood is relatively trivial. By altering or eliminating fru M 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 fru M 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 fru M tunes functional flexibility of a sex circuitry.