SCD1 is required for cell cytokinesis and polarized cell expansion inArabidopsis thaliana

Abstract

In the leaf epidermis, guard mother cells undergo a stereotyped symmetric division to form the guard cells of stomata. We have identified a temperature-sensitive Arabidopsis mutant, stomatal cytokinesis-defective 1-1 (scd1-1), which affects this specialized division. At the non-permissive temperature, 22°C, defective scd1-1 guard cells are binucleate, and the formation of their ventral cell walls is incomplete. Cytokinesis was also disrupted in other types of epidermal cells such as pavement cells. Further phenotypic analysis of scd1-1 indicated a role for SCD1 in seedling growth, root elongation and flower morphogenesis. More severe scd1 T-DNA insertion alleles (scd1-2 and scd1-3) markedly affect polar cell expansion, most notably in trichomes and root hairs. SCD1 is a unique gene in Arabidopsis that encodes a protein related to animal proteins that regulate intracellular protein transport and/or mitogen-activated protein kinase signaling pathways. Consistent with a role for SCD1 in membrane trafficking, secretory vesicles were found to accumulate in cytokinesis-defective scd1 cells. In addition the scd1 mutant phenotype was enhanced by low doses of inhibitors of cell plate consolidation and vesicle secretion. We propose that SCD1 functions in polarized vesicle trafficking during plant cytokinesis and cell expansion.

R1R2R3-Myb proteins positively regulate cytokinesis through activation of KNOLLE transcription in Arabidopsis thaliana

“…A similar defective embryo phenotype has been reported for the kn keule double mutant in which somatic cytokinesis is completely blocked (Waizenegger et al, 2000). The most notable defects of cytokinesis were found in stomata, as reported for other cytokinesisdefective mutants (Falbel et al, 2003;Söllner et al, 2002;Yang et al, 1999). In normal stoma development, a guard mother cell divides symmetrically to produce two guard cells whose closely apposed common cell walls then partially detach from one another to form the pore (Fig.…”

“…Genes in the second class are required for the execution of cytokinesis. Mutations in these genes cause defects in cell plate formation, leading to a common phenotype that is characterized by the formation of multinucleate cells with gapped cell walls or cell wall stubs (Assaad et al, 1996;Yang et al, 1999;Strompen et al, 2002;Lukowitz et al, 1996;Falbel et al, 2003). Genes identified from these mutations encode proteins that are involved in cell plate membrane fusion (Assaad et al, 2001;Lukowitz et al, 1996), biogenesis of primary cell wall (Zuo et al, 2000;Lukowitz et al, 2001) or microtubule array formation or dynamics (Strompen et al, 2002;Soyano et al, 2003;Müller et al, 2004).…”

Virus-induced silencing of NtmybA1 and NtmybA2 causes incomplete cytokinesis and reduced shoot elongation in Nicotiana benthamiana

“…This suggests that these abnormal stomata resulted from a failure of the guard mother cells to undergo cytokinesis. Similar defects in stomata have been found in Arabidopsis plants lacking functional MYB3R1/4 genes and other cytokinesis-defective mutants (Yang et al 1999;Söllner et al 2002;Falbel et al 2003;Haga et al 2007). Less frequently, cytokinesis-defective guard cells contain two nuclei with different sizes, suggesting that chromosome segregation may be also impaired during mitosis ( Figure 3C).…”

Arabidopsis TRAPPII is functionally linked to Rab-A, but not Rab-D in polar protein trafficking intrans-Golgi network

“…A candidate protein that can activate Rab-A early in Golgi would be SCD1, a DENN domain protein (a GEF for Rab35 in mammalian cells 35 ) which is required for polar secretion in cell expansion and cytokinesis. 36 We propose that TRAPPII in plant cells, similar to the action of TRAPPI on Ypt1 in yeast cells, 34 may only act on Rab-A proteins in a late stage in the TGN.…”