The OPAQUE1/DISCORDIA2 myosin XI is required for phragmoplast guidance during asymmetric cell division in maize

Abstract

Formative asymmetric divisions produce cells with different fates and are critical for development. We show the maize (Zea mays) myosin XI protein, OPAQUE1 (O1), is necessary for asymmetric divisions during maize stomatal development. We analyzed stomatal precursor cells before and during asymmetric division to determine why o1 mutants have abnormal division planes. Cell polarization and nuclear positioning occur normally in the o1 mutant, and the future site of division is correctly specified. The defect in o1 becomes apparent during late cytokinesis, when the phragmoplast forms the nascent cell plate. Initial phragmoplast guidance in o1 is normal; however, as phragmoplast expansion continues o1 phragmoplasts become misguided. To understand how O1 contributes to phragmoplast guidance, we identified O1-interacting proteins. Maize kinesins related to the Arabidopsis thaliana division site markers PHRAGMOPLAST ORIENTING KINESINs (POKs), which are also required for correct phragmoplast guidance, physically interact with O1. We propose that different myosins are important at multiple steps of phragmoplast expansion, and the O1 actin motor and POK-like microtubule motors work together to ensure correct late-stage phragmoplast guidance.

De NovoTANGLED1 Recruitment to Aberrant Cell Plate Fusion Sites in Maize

“…We found that accumulation of TAN1-YFP at de novo cell plate insertion sites is partially dependent on the myosin XI O1. We hypothesized that since TAN1 interacts with PHRAGMOPLAST ORIENTING KINESIN1 (POK1) and POK2 (Müller, Han and Smith, 2006; Rasmussen, Sun and Smith, 2011; Mills, Morris and Rasmussen, 2022), and related kinesin 12s interact with myosin XI motor proteins including O1 (Huang et al ., 2022; Nan, Liang, et al ., 2023), O1 might be necessary for TAN1-YFP accumulation. TAN1-YFP fluorescence intensity during telophase was reduced but not absent in both correctly oriented and de novo cell plate fusion sites in o1 compared to wild-type siblings (Figure 4A-B, p = 1.02e-12, One-way ANOVA followed by Tukey’s HSD).…”

“…An invariantly localized asymmetric division generates the small, crescent shaped subsidiary cell and a larger pavement cell (Facette et al ., 2015; Gray, Liu and Facette, 2020; Durney et al ., 2023). Subsidiary cell division positioning is an excellent system due to the consistently positioned divisions and its well-characterized signaling pathways (Frank, Cartwright and Smith, 2003; Cartwright, Humphries and Smith, 2009; Humphries et al ., 2011; Zhang et al ., 2012, 2022; Sutimantanapi, Pater and Smith, 2014; Raissig et al ., 2017; H. Wang et al ., 2019; Wu et al ., 2019; Li et al ., 2021; Ashraf, Liu and Facette, 2023; Durney et al ., 2023; Nan, Char, et al ., 2023; Nan, Liang, et al ., 2023).…”

From grasses to succulents – development and function of distinct stomatal subsidiary cells

“…Upon chromosomal segregation, the phragmoplast forms between the two daughter nuclei to form the curved SC wall. During this process, the myosin XI protein OPAQUE1/DCD2 is required for late‐stage phragmoplast guidance (Nan et al ., 2023b).…”

Charting the course of asymmetric cell division in maize: The crucial role of OPAQUE1 in guiding the phragmoplast

“…In this issue, Qiong Nan and colleagues ( Nan et al 2023 ) aimed to learn how plant cells correctly execute the asymmetric division of maize ( Zea mays ) SMCs. In previous research, it was shown that actin motors and myosins are key components of SMC division during polarization, establishing division planes and/or cytokinesis.…”

“…In o1 mutants, the phragmoplast becomes misguided following initial contact, leading to aberrant division planes. Adapted from Nan et al (2023) , Figure 9.…”