Genetic and molecular studies of thenod locus: A putative microtubule motor required in Drosophila female meiosis

Abstract

The female-specific {dollar}nod\sp{lcub}a{rcub}{dollar} mutation induces meiotic nondisjunction of nonexchange chromosomes in the distributive system, and the mitotic loss of maternally derived chromosomes in early cleavage divisions. Eight new nod alleles were isolated. They are all recessive and phenotypically similar to {dollar}nod\sp{lcub}a{rcub}{dollar}; thus the pleiotropic effects of {dollar}nod\sp{lcub}a{rcub}{dollar} on meiosis and early mitosis are a general property of mutations at this locus. These new alleles were induced on a multiply-inverted {dollar}X{dollar} chromosome (FM7), which strongly suppresses {dollar}X{dollar}-chromosomal exchange in FM7,nod/{dollar}nod\sp{lcub}a{rcub}{dollar} females. Consequently, {dollar}X{dollar} chromosome nondisjunction and mitotic loss are greatly intensified.;The genomic DNA sequence corresponding to the {dollar}nod{dollar} locus has been cloned by chromosome walk, and the gene was identified by restriction fragment length polymorphisms. The nod transcript was identified on the basis of its female specificity and its absence or altered size in animals bearing either of two nod alleles. nod cDNA clones containing the entire open reading frame have also been isolated and sequenced. The amino terminal (350 a.a.) of the predicted nod protein is homologous to the kinesin protein, including the ATP and microtubule binding sites. Thus, the nod gene encodes a putative microtubule motor which is required for the segregation of nonexchange chromosomes in Drosophila females. The nod gene is also transcribed in the embryonic, larval, and pupal stages of development, and possibly in all dividing cells. Thus the nod gene product may be involved in mitosis as well as in meiosis.