Kinetochore, a protein super$B!>(Bcomplex on the centromere of chromosomes,
controls chromosome segregation during cell division. The NDC80 complex,
made up of NDC80, NUF2, SPC24 and SPC25 proteins, connects spindle fibers to
the kinetochore. While it is found in most species, functional studies of
this complex are rare in Arabidopsis.
The team of Jinwoo Shin from Seoul National University in South Korea
characterizes a recessive mutant, meristem unstructured$B!>(B1 (mun$B!>(B1), which
exhibits an abnormal phenotype with unstructured shoot apical meristem
caused by expression of the WUSCHEL gene in unexpected tissues. The mutant
also exhibits stunted growth, embryo arrest, DNA aneuploidy, and defects in
chromosome segregation with a low cell division rate.
Null mutants of MUN generated via TALEN and CRISPR-Cas9 techniques showed
the same embryo lethality as mun-1 as well as with another recessive mutant,
nuf2-1. Interactions of the components of the NDC80 complex were confirmed
and that absence of any one of the four proteins involved would result in
malfunction of kinetochore components.
These results reveal that MUN is a homolog of SPC24 in Arabidopsis, which is
required for proper cell division.