De Novo TANGLED1 recruitment from the phragmoplast to aberrant cell plate fusion sites in maize.

Division plane positioning is critical for proper growth and development in many organisms. In plants, the division plane is established before mitosis, by accumulation of a cytoskeletal structure called the preprophase band (PPB). The PPB is thought to be essential for recruitment of division site localized proteins, which remain at the division site after the PPB disassembles. Here, we show that a division site localized protein, TANGLED1 (TAN1), is recruited independently of the PPB to the cell cortex by the plant cytokinetic machinery, the phragmoplast, using the PPB-defective mutant discordia1 and chemical treatments that disrupt the phragmoplast. TAN1 recruitment to de novo sites on the cortex is partially dependent on intact actin filaments and the myosin XI motor protein OPAQUE1 (O1). These data imply a yet unknown role for TAN1 and possibly other division site localized proteins during the last stages of cell division when the phragmoplast touches the cell cortex to complete cytokinesis.

De Novo TANGLED1 Recruitment to Aberrant Cell Plate Fusion Sites in Maize.

Division plane positioning is critical for proper growth and development in many organisms. In plants, the division plane is established before mitosis, by accumulation of a cytoskeletal structure called the preprophase band (PPB). The PPB is thought to be essential for recruitment of division site localized proteins, which remain at the division site after the PPB disassembles. Here, we show that a division site localized protein, TANGLED1 (TAN1), is recruited independently of the PPB to the cell cortex at sites, by the plant cytokinetic machinery, the phragmoplast. TAN1 recruitment to de novo sites on the cortex is partially dependent on intact actin filaments and the myosin XI motor protein OPAQUE1 (O1). These data imply a yet unknown role for TAN1 and possibly other division site localized proteins during the last stages of cell division when the phragmoplast touches the cell cortex to complete cytokinesis.

Subcellular positioning during cell division and cell plate formation in maize.

Introduction: During proliferative plant cell division, the new cell wall, called the cell plate, is first built in the middle of the cell and then expands outward to complete cytokinesis. This dynamic process requires coordinated movement and arrangement of the cytoskeleton and organelles. Methods: Here we use live-cell markers to track the dynamic reorganization of microtubules, nuclei, endoplasmic reticulum, and endomembrane compartments during division and the formation of the cell plate in maize leaf epidermal cells. Results: The microtubule plus-end localized protein END BINDING1 (EB1) highlighted increasing microtubule dynamicity during mitosis to support rapid changes in microtubule structures. The localization of the cell-plate specific syntaxin KNOLLE, several RAB-GTPases, as well as two plasma membrane localized proteins was assessed after treatment with the cytokinesis-specific callose-deposition inhibitor Endosidin7 (ES7) and the microtubule-disrupting herbicide chlorpropham (CIPC). While ES7 caused cell plate defects in Arabidopsis thaliana, it did not alter callose accumulation, or disrupt cell plate formation in maize. In contrast, CIPC treatment of maize epidermal cells occasionally produced irregular cell plates that split or fragmented, but did not otherwise disrupt the accumulation of cell-plate localized proteins. Discussion: Together, these markers provide a robust suite of tools to examine subcellular trafficking and organellar organization during mitosis and cell plate formation in maize.