The WD40 Repeat Protein NEDD1 Functions in Microtubule Organization during Cell Division inArabidopsis thaliana 

Abstract

Although cells of flowering plants lack a structurally defined microtubule-organizing center like the centrosome, organization of the spindles and phragmoplasts in mitosis is known to involve the evolutionarily conserved g-tubulin complex. We have investigated the function of Arabidopsis thaliana NEDD1, a WD40 repeat protein related to the animal NEDD1/GCP-WD protein, which interacts with the g-tubulin complex. The NEDD1 protein decorates spindle microtubules (MTs) preferentially toward spindle poles and phragmoplast MTs toward their minus ends. A T-DNA insertional allele of the single NEDD1 gene was isolated and maintained in heterozygous sporophytes, and NEDD1's function in cell division was analyzed in haploid microspores produced by the heterozygote. In approximately half of the dividing microspores exhibiting aberrant MT organization, spindles were no longer restricted to the cell periphery and became abnormally elongated. After mitosis, MTs aggregated between reforming nuclei but failed to appear in a bipolar configuration. Consequently, defective microspores did not form a continuous cell plate, and two identical nuclei were produced with no differentiation into generative and vegetative cells. Our results support the notion that the plant NEDD1 homolog plays a critical role in MT organization during mitosis, and its function is likely linked to that of the g-tubulin complex.

ArabidopsisCortical Microtubules Are Initiated along, as Well as Branching from, Existing Microtubules

“…In animal cells, neural precursor cell expressed developmentally downregulated protein 1 (NEDD1), targets the gamma tubulin ring complex to the centrosome (Fant et al, 2009). In plants, NEDD1 decorates the spindle poles of plant cells (Zeng et al, 2009) and during interphase labels cytoplasmic spots associated with cortical microtubules (Motose et al, 2008). We therefore used it as a potential marker of microtubule nucleation sites.…”

TONNEAU2/FASS Regulates the Geometry of Microtubule Nucleation and Cortical Array Organization in Interphase Arabidopsis Cells

“…Biochemical isolations have shown that core proteins are assembled into a complex with stoichiometry similar to the g-TURCs from yeast and animals (Nakamura et al, 2010). g-TURC components g-tubulin, GCP2, GCP4, and GCP-WD have been shown to play an essential role in organization of cortical microtubules, the spindle, and phragmoplast arrays in Arabidopsis thaliana (Binarová et al, 2006;Pastuglia et al, 2006;Nakamura and Hashimoto, 2009;Zeng et al, 2009;Kong et al, 2010).…”

Update: Plant Cortical Microtubule Arrays

“…Another peripheral protein, conserved across eukaryotes, is NEURAL PRECURSOR CELL EXPRESSED DEVELOPMENTALLY DOWN-REGULATED PRO-TEIN1 (NEDD1), also known as GCP-WD. NEDD1/ GCP-WD localizes g-TuRC within mitotic spindles in human cells (Haren et al, 2006;Lüders et al, 2006) and was shown to be required for normal cell division in plants (Zeng et al, 2009). NEDD1/GCP-WD localizes g-TuRC within interphase arrays in plants, where it increases the ratio of branch to parallel nucleation (Walia et al, 2014).…”