fruitless tunes functional flexibility of courtship circuitry during development.

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 toward females, while its function during adulthood is involved in inhibiting male-male courtship. 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 instead of switching on its function as conventionally viewed.

Chen J ，Jin S ，Chen D ，Cao J ，Ji X ，Peng Q ，Pan Y ... -  《eLife》

From fruitless to sex: On the generation and diversification of an innate behavior.

Male sexual behavior in Drosophila melanogaster, largely controlled by the fruitless (fru) gene encoding the male specific FruM protein, is among the best studied animal behaviors. Although substantial studies suggest that FruM specifies a neuronal circuitry governing all aspects of male sexual behaviors, recent findings show that FruM is not absolutely necessary for such behaviors. We propose that another regulatory gene doublesex encoding the male-specific DsxM protein builds a core neuronal circuitry that possesses the potential for courtship, which could be either induced through adult social experience or innately manifested during development by FruM expression in a broader neuronal circuitry. FruM expression levels and patterns determine the modes of courtship behavior from innate heterosexual, homosexual, bisexual, to learned courtship. We discuss how FruM expression is regulated by hormones and social experiences and tunes functional flexibility of the sex circuitry. We propose that regulatory genes hierarchically build the potential for innate and learned aspects of courtship behaviors, and expression changes of these regulatory genes among different individuals and species with different social experiences ultimately lead to behavioral diversification.

Peng Q ，Chen J ，Pan Y 《-》

Genetic identification and separation of innate and experience-dependent courtship behaviors in Drosophila.

Wild-type D. melanogaster males innately possess the ability to perform a multistep courtship ritual to conspecific females. The potential for this behavior is specified by the male-specific products of the fruitless (fru(M)) gene; males without fru(M) do not court females when held in isolation. We show that such fru(M) null males acquire the potential for courtship when grouped with other flies; they apparently learn to court flies with which they were grouped, irrespective of sex or species and retain this behavior for at least a week. The male-specific product of the doublesex gene (dsx(M)) is necessary and sufficient for the acquisition of the potential for such experience-dependent courtship. These results reveal a process that builds, via dsx(M) and social experience, the potential for a more flexible sexual behavior, which could be evolutionarily conserved as dsx-related genes that function in sexual development are found throughout the animal kingdom.

Pan Y ，Baker BS 《-》

Cellular and behavioral functions of fruitless isoforms in Drosophila courtship.

Male-specific products of the fruitless (fru) gene control the development and function of neuronal circuits that underlie male-specific behaviors in Drosophila, including courtship. Alternative splicing generates at least three distinct Fru isoforms, each containing a different zinc-finger domain. Here, we examine the expression and function of each of these isoforms. We show that most fru(+) cells express all three isoforms, yet each isoform has a distinct function in the elaboration of sexually dimorphic circuitry and behavior. The strongest impairment in courtship behavior is observed in fru(C) mutants, which fail to copulate, lack sine song, and do not generate courtship song in the absence of visual stimuli. Cellular dimorphisms in the fru circuit are dependent on Fru(C) rather than other single Fru isoforms. Removal of Fru(C) from the neuronal classes vAB3 or aSP4 leads to cell-autonomous feminization of arborizations and loss of courtship in the dark. These data map specific aspects of courtship behavior to the level of single fru isoforms and fru(+) cell types-an important step toward elucidating the chain of causality from gene to circuit to behavior.

von Philipsborn AC ，Jörchel S ，Tirian L ，Demir E ，Morita T ，Stern DL ，Dickson BJ ... -  《-》

Generation and characterization of fruitless P1 promoter mutant in Drosophila melanogaster.

Neville MC ，Eastwood A ，Allen AM ，de Haan A ，Nojima T ，Goodwin SF ... -  《-》