Maternally expressed and partially redundant beta-tubulins in Caenorhabditis elegans are autoregulated.
The mitotic spindle, which partitions replicated chromosomes to daughter cells during cell division, is composed of microtubule assemblies of alpha/beta-tubulin heterodimers. Positioning of the mitotic spindle influences the size and location of daughter cells, and can be important for the proper partitioning of developmental determinants. We describe two semi-dominant mis-sense mutations in tbb-2, one of two C. elegans beta-tubulin genes that are maternally expressed and together are required for microtubule-dependent processes in the early embryo. These mutations result in a posteriorly displaced and misoriented mitotic spindle during the first cell division. In contrast, a probable tbb-2 null allele is recessive, and when homozygous results in less severe spindle positioning defects and only partially penetrant embryonic lethality. Two of the tbb-2 mutations result in reduced levels of TBB-2 protein, and increased levels of a second maternally expressed beta-tubulin, TBB-1. However, levels of TBB-1 are not increased in a tbb-2 mutant with an allele that does not result in reduced levels of TBB-2 protein. We conclude that feedback regulation influences maternal beta-tubulin expression in C. elegans, but cannot fully restore normal microtubule function in the absence of one beta-tubulin isoform.
Ellis
Gregory C
GC
Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA.
Phillips
Jennifer B
JB
O'Rourke
Sean
S
Lyczak
Rebecca
R
Bowerman
Bruce
B
D000483:Alleles; D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology / Q000196:embryology / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D004625:Embryo, Nonmammalian / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000378:metabolism*; D008938:Mitosis; D009154:Mutation; D008941:Spindle Apparatus / Q000378:metabolism*; D014404:Tubulin / Q000235:genetics / Q000378:metabolism*
D029742:Caenorhabditis elegans Proteins; D014404:Tubulin