The kinetochore protein NNF1 has a moonlighting role in the vegetative development of Arabidopsis thaliana.

The kinetochore is a supramolecular protein complex assembled on the chromosomes, essential for faithful segregation of the genome during cell divisions. More than 100 proteins are known to constitute the eukaryotic kinetochore architecture, primarily identified using non-plant organisms. A majority of them are fast evolving and are under positive selection. Thus, functional characterization of the plant kinetochore proteins is limited as only a few conserved orthologs sharing sequence similarities with their animal counterparts have been examined. Here, we report the functional characterization of the Arabidopsis thaliana homolog of the yeast NNF1/human PMF1 outer kinetochore protein and show that it has both kinetochore and non-kinetochore functions in plant growth and development. Knockout of NNF1 causes embryo lethality implying its essential role in cell division. AtNNF1 interacts with MIS12 in a Y2H and co-immuno pull down assay, confirming it as one of the constituents of the plant MIS12 complex. GFP-NNF1 localizes to the kinetochore, rescuing the embryo lethal nnf1-1-/- phenotype, but the rescued plants (GFP-NNF1nnf1-/- ) are dwarf displaying hypomorphic phenotypes with no evidence of mitotic or meiotic segregation defects. GFP-NNF1nnf1-/- dwarf plants have reduced levels of endogenous polyamines, which are partially rescued to WT upon exogenous application of polyamines. Mutations in the putative leucine zipper binding motif of NNF1 gave rise to a dominant-negative tall plant phenotype reminiscent of constitutive gibberellin action. These contrasting hypomorphic dwarf and anti morphic tall phenotypes facilitated us to attribute a moonlighting role for Arabidopsis NNF1 affecting polyamine and gibberellin metabolism other than its primary role in kinetochores.