Revisiting the X:A signal that specifies Caenorhabditis elegans sexual fate.
In Caenorhabditis elegans, sex is determined by the opposing actions of X-signal elements (XSEs) and autosomal signal elements (ASEs), which communicate the ratio of X chromosomes to sets of autosomes (X:A signal). This study delves more deeply into the mechanism by which XSEs transmit X chromosome dose. We determined the relative contributions of individual XSEs to the X:A signal and showed the order of XSE strength to be sex-1 > sex-2 > fox-1 > ceh-39 >/= region 1 XSE. sex-1 exerts a more potent influence on sex determination and dosage compensation than any other XSE by functioning in two separate capacities in the pathway: sex-1 acts upstream as an XSE to repress xol-1 and downstream as an activator of hermaphrodite development and dosage compensation. Furthermore, the process of dosage compensation affects expression of the very XSEs that control it; XSEs become fully dosage compensated once sex is determined. The X:A signal is then equivalent between XO and XX animals, causing sexual differentiation to be controlled by genes downstream of xol-1 in the sex-determination pathway. Prior to the onset of dosage compensation, the difference in XSE expression between XX and XO embryos appears to be greater than twofold, making X chromosome counting a robust process.
Gladden
John M
JM
Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3204, USA.
Farboud
Behnom
B
Meyer
Barbara J
BJ
D000818:Animals; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000196:embryology* / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D018509:DNA, Helminth / Q000235:genetics; D012734:Disorders of Sex Development / Q000196:embryology / Q000235:genetics; D004303:Dosage Compensation, Genetic; D005246:Feedback; D005260:Female; D017238:Genes, Helminth; D008297:Male; D008957:Models, Genetic; D009154:Mutation; D034622:RNA Interference; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics; D019849:Sex Determination Processes; D012733:Sex Differentiation; D015398:Signal Transduction; D014960:X Chromosome / Q000235:genetics*
D029742:Caenorhabditis elegans Proteins; D017931:DNA Primers; D018509:DNA, Helminth; D018160:Receptors, Cytoplasmic and Nuclear; C115677:sex-1 protein, C elegans