**Group 1: Phragmoplast Structure and Function**
– Phragmoplast is composed of microtubules, microfilaments, and endoplasmic reticulum elements.
– It forms between daughter nuclei during anaphase and telophase.
– Cell plate formation occurs within the phragmoplast structure.
– Microtubules guide vesicles carrying cell wall material to the growing cell plate.
– Smooth endoplasmic reticulum segments trapped within the cell plate later form plasmodesmata.
– Phragmoplast emerges from spindle microtubules after anaphase.
– Actin filaments aid in phragmoplast expansion during telophase.
– Various microtubule-associated proteins (MAPs) play crucial roles in membrane fusion and microtubule bundling at the midline.
**Group 2: Proteins Involved in Phragmoplast**
– MAP65-3 and kinesin-5 are crucial for antiparallel microtubule bundling at the midline.
– Kinesin-7 family proteins recruit a MAPK cascade to the midline.
– Phosphorylated MAP65-1 reduces microtubule bundling for cell plate expansion.
– Kinesin-12 members, PAKRP1 and PAKRP1L, are essential for cytokinesis during male gametogenesis.
– TPLATE, an adaptin-like protein, is necessary for cytokinesis.
**Group 3: Actin Filaments in Phragmoplast**
– Actin filaments localize to the phragmoplast and aid in expansion.
– Disorganization of actin filaments delays cell-plate expansion.
– Actin filaments play a significant role in expansion during telophase.
– Changes in actin microfilament contribution affect cell plate development.
**Group 4: Kinesin-5 and MAP Kinase in Cytokinesis**
– Kinesin-5 plays a conserved role in plant mitosis.
– Understanding kinesin-5 function provides insights into plant development.
– MAP kinase is cell cycle regulated and aids in cytokinesis in tobacco cells.
– Inhibition of MAP kinase activity can impact cell plate expansion during cytokinesis.
**Group 5: Kinesin-Like Proteins and Signaling Modules in Cytokinesis**
– Kinesin-like proteins are involved in cell plate expansion during plant cytokinesis.
– HINKEL kinesin and ANP MAPKKKs constitute a pathway essential for cytokinesis.
– CDK-mediated phosphorylation of kinesin-like proteins is crucial for the transition to cytokinesis.
– Signaling pathways involving kinases and kinesins are vital for successful cytokinesis in plant cells.
The phragmoplast is a plant cell specific structure that forms during late cytokinesis. It serves as a scaffold for cell plate assembly and subsequent formation of a new cell wall separating the two daughter cells. The phragmoplast can only be observed in Phragmoplastophyta, a clade that includes the Coleochaetophyceae, Zygnematophyceae, Mesotaeniaceae, and Embryophyta (land plants). Some algae use another type of microtubule array, a phycoplast, during cytokinesis.
