Synaptonemal complex analysis of the X1X2Y trivalent in Mantis religiosa L. males: inferences on the origin and maintenance of the sex-determining mechanism.
Characterization of sex chromosomes in males of Mantis religiosa L. (2n = 24 + X1X2Y) was carried out by C-banding, silver staining and fluorescence in situ hybridization. They are meta- or submetacentric, their arms being designated as X1L, X1R, X2R, X2L, YL and YR. Meiotic behaviour of the sex trivalent was examined through the analysis of synaptonemal complexes (SCs), prometaphase I (metaphase I) and metaphase II nuclei. On the basis of the SC analysis, chromosomal length measurements at mitosis and prometaphase I and data from several orthopteran species, it is proposed that the breakpoints of the reciprocal translocation that originated this complex sex-determining mechanism were close to the centromeres of the X and the largest autosome, and that the asynapsed X1L and X2R regions observed in the sex trivalent at pachytene represent the original X chromosome. The X centromere being probably that of the X2 element because it lacks a partner in the SC pachytene trivalent. The relationship among synaptic pattern, chiasma localization and balanced segregation of the sex trivalent is also discussed.
del Cerro
A L
AL
Departamento de Genética, Facultad de Biología, Universidad Complutense, Madrid, Spain.
Cuñado
N
N
Santos
J L
JL
D000818:Animals; D002871:Chromosome Banding; D008297:Male; D009987:Orthoptera / Q000166:cytology / Q000235:genetics*; D019849:Sex Determination Processes; D013030:Spain; D013573:Synaptonemal Complex / Q000235:genetics*; D014178:Translocation, Genetic; D014960:X Chromosome / Q000235:genetics* / Q000648:ultrastructure; D014998:Y Chromosome / Q000235:genetics* / Q000648:ultrastructure