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 which includes the Embryophyta. Some algae use another type of microtubule array, a phycoplast, during cytokinesis.
The phragmoplast is a complex assembly of microtubules (MTs), microfilaments (MFs), and endoplasmic reticulum (ER) elements, that assemble in two opposing sets perpendicular to the plane of the future cell plate during anaphase and telophase. It is initially barrel-shaped and forms from the mitotic spindle between the two daughter nuclei while nuclear envelopes reassemble around them. The cell plate initially forms as a disc between the two halves of the phragmoplast structure. While new cell plate material is added to the edges of the growing plate, the phragmoplast microtubules disappear in the center and regenerate at the edges of the growing cell plate. The two structures grow outwards until they reach the outer wall of the dividing cell. If a phragmosome was present in the cell, the phragmoplast and cell plate will grow through the space occupied by the phragmosome. They will reach the parent cell wall exactly at the position formerly occupied by the preprophase band.
The microtubules and actin filaments within the phragmoplast serve to guide vesicles with cell wall material to the growing cell plate. Actin filaments are also possibly involved in guiding the phragmoplast to the site of the former preprophase band location at the parent cell wall. While the cell plate is growing, segments of smooth endoplasmic reticulum are trapped within it, later forming the plasmodesmata connecting the two daughter cells.
The phragmoplast can be differentiated topographically into two areas, the midline that includes the central plane where some of the plus-ends of both anti-parallel sets of microtubules (MTs) interdigitate (as in the midbody matrix), and the distal regions at both sides of the midline.
Role in the Plant Cell Cycle
After anaphase, the phragmoplast emerges from the remnant spindle MTs in between the daughter nuclei. MT plus ends overlap the equator of phragmoplast at the site where the cell plate will form. The formation of the cell plate depends on localized secretory vesicle fusion to deliver membrane and cell-wall components. Excess membrane lipid and cell-wall components are recycled by clathrin/dynamin-dependent retrograde membrane traffic. Once the initial cell plate forms at its center, the phragmoplast begins to expand outward to reach the cell edges. Actin filaments also localize to phragmoplast and accumulate greatly at late telophase. Evidence suggests that actin filaments serve phragmoplast expansion more than initial organization, given that disorganization of actin filaments via drug treatments lead to the delay of cell-plate expansion.
Many microtubule-associated proteins (MAPs) have been localized to the phragmoplast, including both constitutively expressed ones (such as MOR1, katanin, CLASP, SPR2, and γ-tubulin complex proteins) and those expressed specifically during M-phase, such as EB1c, TANGLED1 and augmin complex proteins. The functions of these proteins in the phragmoplast are presumably similar to their functions elsewhere in the cell. Most research into phragmoplast MAPs have been focused on the midline because it is, first, where most of the membrane fusion takes place and, second, where the two sets of anti-parallel MTs are held together. The discovery of an important variety of molecules that localize to the phragmoplast midline is shedding light on the complex processes operating in this phragmoplast region.
Two proteins that have critical functions for antiparallel MT bundling at the phragmoplast midline are MAP65-3 and kinesin-5. The kinesin-7 family proteins, HINKEL/AtNACK1 and AtNACK2/TES, recruit a mitogen-activated protein kinase (MAPK) cascade to the midline and induce MAP65 phosphorylation. Phosphorylated MAP65-1 also accumulates at the midline and reduces MT-bundling activities for cell-plate expansion. The essential mechanism of MAPK cascade for phragmoplast expansion is suppressed by cyclin dependent kinase (CDK) activity before telophase.
Certain phragmoplast midline-accumulating MAPs are essential proteins for cytokinesis. The kinesin-12 members, PAKRP1 and PAKRP1L, accumulate at the midline and double loss-of-function mutants have defective cytokinesis during male gametogenesis. PAKRP2 accumulates at midline and also in puncta throughout the phragmoplast, which implies that PAKRP2 participates in Golgi-derived vesicle transport. Moss homologs of PAKRP2, KINID1a, and KINID1b localize to the phragmoplast midline and are essential for phragmoplast organization. RUNKEL, which is a HEAT repeat-containing MAP, also accumulates at the midline and cytokinesis is aberrant in lines with the loss-of-function mutations in this protein. Another midline-localized protein, “two-in-on” (TIO), is a putative kinase and is also required for cytokinesis as shown by defects in a mutant. TIO interacts with PAKRP1, PAKRP1L (kinesin-12), and NACK2/TES (kinesin-7) according to the yeast two hybrid assays. Finally, TPLATE, an adaptin-like protein, accumulates at the cell plate and is essential for cytokinesis
- P.H. Raven, R.F. Evert, S.E. Eichhorn (2005): Biology of Plants, 7th Edition, W.H. Freeman and Company Publishers, New York, ISBN 0-7167-1007-2
- Pickett-Heaps, J. (1976). "Cell division in eucaryotic algae". BioScience. 26 (7): 445–450. doi:10.2307/1297481.
- Otegui, Marisa S.; Verbrugghe, Koen J.; Skop, Ahna R. (August 2005). "Midbodies and phragmoplasts: analogous structures involved in cytokinesis". Trends in Cell Biology. 15 (8): 404–413. doi:10.1016/j.tcb.2005.06.003. ISSN 0962-8924. PMC . PMID 16009554.
- Hamada, Takahiro (2014-01-01). "Microtubule Organization and Microtubule-Associated Proteins in Plant Cells". International Review of Cell and Molecular Biology. 312: 1–52. doi:10.1016/B978-0-12-800178-3.00001-4. ISSN 1937-6448.
- Müller, Sabine (2012-04-01). "Universal rules for division plane selection in plants". Protoplasma. 249 (2): 239–253. doi:10.1007/s00709-011-0289-y. ISSN 0033-183X.
- Higaki, Takumi; Kutsuna, Natsumaro; Sano, Toshio; Hasezawa, Seiichiro (2008-07-17). "Quantitative analysis of changes in actin microfilament contribution to cell plate development in plant cytokinesis". BMC Plant Biology. 8: 80. doi:10.1186/1471-2229-8-80. ISSN 1471-2229.
- Whittington, Angela T.; Vugrek, Oliver; Wei, Ke Jun; Hasenbein, Nortrud G.; Sugimoto, Keiko; Rashbrooke, Madeleine C.; Wasteneys, Geoffrey O. (May 2001). "MOR1 is essential for organizing cortical microtubules in plants". Nature. 411 (6837): 610–613. doi:10.1038/35079128. ISSN 1476-4687.
- Komaki, Shinichiro; Abe, Tatsuya; Coutuer, Silvie; Inzé, Dirk; Russinova, Eugenia; Hashimoto, Takashi (2010-02-01). "Nuclear-localized subtype of end-binding 1 protein regulates spindle organization in Arabidopsis". J Cell Sci. 123 (3): 451–459. doi:10.1242/jcs.062703. ISSN 0021-9533. PMID 20067996.
- Martinez, Pablo; Luo, Anding; Sylvester, Anne; Rasmussen, Carolyn G. (2017-03-07). "Proper division plane orientation and mitotic progression together allow normal growth of maize". Proceedings of the National Academy of Sciences. 114 (10): 2759–2764. doi:10.1073/pnas.1619252114. ISSN 0027-8424. PMC . PMID 28202734.
- Ho, Chin-Min Kimmy; Hotta, Takashi; Kong, Zhaosheng; Zeng, Cui Jing Tracy; Sun, Jie; Lee, Yuh-Ru Julie; Liu, Bo (2011-07-01). "Augmin Plays a Critical Role in Organizing the Spindle and Phragmoplast Microtubule Arrays in Arabidopsis". The Plant Cell. 23 (7): 2606–2618. doi:10.1105/tpc.111.086892. ISSN 1040-4651. PMC . PMID 21750235.
- Ho, Chin-Min Kimmy; Hotta, Takashi; Guo, Fengli; Roberson, Robert W.; Lee, Yuh-Ru Julie; Liu, Bo (2011-08-01). "Interaction of Antiparallel Microtubules in the Phragmoplast Is Mediated by the Microtubule-Associated Protein MAP65-3 in Arabidopsis". The Plant Cell. 23 (8): 2909–2923. doi:10.1105/tpc.110.078204. ISSN 1040-4651. PMC . PMID 21873565.
- Bannigan, Alex; Scheible, Wolf-Rüdiger; Lukowitz, Wolfgang; Fagerstrom, Carey; Wadsworth, Patricia; Somerville, Chris; Baskin, Tobias I. (2007-08-15). "A conserved role for kinesin-5 in plant mitosis". Journal of Cell Science. 120 (16): 2819–2827. doi:10.1242/jcs.009506. ISSN 0021-9533. PMID 17652157.
- Calderini, O.; Bögre, L.; Vicente, O.; Binarova, P.; Heberle-Bors, E.; Wilson, C. (October 1998). "A cell cycle regulated MAP kinase with a possible role in cytokinesis in tobacco cells". Journal of Cell Science. 111 (20): 3091–3100. ISSN 0021-9533. PMID 9739082.
- Kosetsu, Ken; Matsunaga, Sachihiro; Nakagami, Hirofumi; Colcombet, Jean; Sasabe, Michiko; Soyano, Takashi; Takahashi, Yuji; Hirt, Heribert; Machida, Yasunori (2010-11-01). "The MAP Kinase MPK4 Is Required for Cytokinesis in Arabidopsis thaliana". The Plant Cell. 22 (11): 3778–3790. doi:10.1105/tpc.110.077164. ISSN 1040-4651. PMC . PMID 21098735.
- Nishihama, Ryuichi; Soyano, Takashi; Ishikawa, Masaki; Araki, Satoshi; Tanaka, Hirokazu; Asada, Tetsuhiro; Irie, Kenji; Ito, Mayumi; Terada, Mizuya (2002-04-05). "Expansion of the cell plate in plant cytokinesis requires a kinesin-like protein/MAPKKK complex". Cell. 109 (1): 87–99. doi:10.1016/s0092-8674(02)00691-8. ISSN 0092-8674. PMID 11955449.
- Takahashi, Yuji; Soyano, Takashi; Kosetsu, Ken; Sasabe, Michiko; Machida, Yasunori (October 2010). "HINKEL kinesin, ANP MAPKKKs and MKK6/ANQ MAPKK, which phosphorylates and activates MPK4 MAPK, constitute a pathway that is required for cytokinesis in Arabidopsis thaliana". Plant & Cell Physiology. 51 (10): 1766–1776. doi:10.1093/pcp/pcq135. ISSN 1471-9053. PMC . PMID 20802223.
- Sasabe, Michiko; Soyano, Takashi; Takahashi, Yuji; Sonobe, Seiji; Igarashi, Hisako; Itoh, Tomohiko J.; Hidaka, Mikiko; Machida, Yasunori (2006-04-15). "Phosphorylation of NtMAP65-1 by a MAP kinase down-regulates its activity of microtubule bundling and stimulates progression of cytokinesis of tobacco cells". Genes & Development. 20 (8): 1004–1014. doi:10.1101/gad.1408106. ISSN 0890-9369. PMC . PMID 16598040.
- Sasabe, Michiko; Boudolf, Véronique; Veylder, Lieven De; Inzé, Dirk; Genschik, Pascal; Machida, Yasunori (2011-10-25). "Phosphorylation of a mitotic kinesin-like protein and a MAPKKK by cyclin-dependent kinases (CDKs) is involved in the transition to cytokinesis in plants". Proceedings of the National Academy of Sciences. 108 (43): 17844–17849. doi:10.1073/pnas.1110174108. ISSN 0027-8424. PMC . PMID 22006334.
- Pan, Ruiqin; Lee, Y.-R. Julie; Liu, Bo (2004). "Localization of two homologous Arabidopsis kinesin-related proteins in the phragmoplast". Planta. 220 (1): 156–164. doi:10.1007/s00425-004-1324-4. JSTOR 23388676.
- Lee, Yuh-Ru Julie; Li, Yan; Liu, Bo (2007-08-01). "Two Arabidopsis Phragmoplast-Associated Kinesins Play a Critical Role in Cytokinesis during Male Gametogenesis". The Plant Cell. 19 (8): 2595–2605. doi:10.1105/tpc.107.050716. ISSN 1040-4651. PMC . PMID 17720869.
- Lee, Y. R.; Giang, H. M.; Liu, B. (November 2001). "A novel plant kinesin-related protein specifically associates with the phragmoplast organelles". The Plant Cell. 13 (11): 2427–2439. doi:10.1105/tpc.13.11.2427. ISSN 1040-4651. PMC . PMID 11701879.
- Hiwatashi, Yuji; Obara, Mari; Sato, Yoshikatsu; Fujita, Tomomichi; Murata, Takashi; Hasebe, Mitsuyasu (November 2008). "Kinesins Are Indispensable for Interdigitation of Phragmoplast Microtubules in the Moss Physcomitrella patens". The Plant Cell. 20 (11): 3094–3106. doi:10.1105/tpc.108.061705. ISSN 1040-4651. PMC . PMID 19028965.
- Krupnova, Tamara; Sasabe, Michiko; Ghebreghiorghis, Luam; Gruber, Christian W.; Hamada, Takahiro; Dehmel, Verena; Strompen, Georg; Stierhof, York-Dieter; Lukowitz, Wolfgang; Kemmerling, Birgit; Machida, Yasunori; Hashimoto, Takashi; Mayer, Ulrike; Jürgens, Gerd (2009-03-24). "Microtubule-Associated Kinase-like Protein RUNKEL Needed for Cell Plate Expansion in Arabidopsis Cytokinesis". Current Biology. 19 (6): 518–523. doi:10.1016/j.cub.2009.02.021. ISSN 0960-9822.
- Krupnova, Tamara; Stierhof, York-Dieter; Hiller, Ulrike; Strompen, Georg; Müller, Sabine (2013-06-01). "The microtubule-associated kinase-like protein RUNKEL functions in somatic and syncytial cytokinesis". The Plant Journal. 74 (5): 781–791. doi:10.1111/tpj.12160. ISSN 1365-313X.
- Aeong Oh, Sung; Johnson, Andrew; Smertenko, Andrei; Rahman, Daisy; Ki Park, Soon; Hussey, Patrick J.; Twell, David (2005-12-06). "A Divergent Cellular Role for the FUSED Kinase Family in the Plant-Specific Cytokinetic Phragmoplast". Current Biology. 15 (23): 2107–2111. doi:10.1016/j.cub.2005.10.044. ISSN 0960-9822.
- Oh, Sung Aeong; Bourdon, Valérie; Dickinson, Hugh G.; Twell, David; Park, Soon Ki (2014-03-01). "Arabidopsis Fused kinase TWO-IN-ONE dominantly inhibits male meiotic cytokinesis". Plant Reproduction. 27 (1): 7–17. doi:10.1007/s00497-013-0235-6. ISSN 2194-7953.
- Oh, Sung Aeong; Allen, Trudie; Kim, Gyun Jang; Sidorova, Anna; Borg, Michael; Park, Soon Ki; Twell, David (October 2012). "Arabidopsis Fused kinase and the Kinesin-12 subfamily constitute a signalling module required for phragmoplast expansion". The Plant Journal: For Cell and Molecular Biology. 72 (2): 308–319. doi:10.1111/j.1365-313X.2012.05077.x. ISSN 1365-313X. PMID 22709276.
- Damme, Daniël Van; Coutuer, Silvie; Rycke, Riet De; Bouget, Francois-Yves; Inzé, Dirk; Geelen, Danny (2006-12-01). "Somatic Cytokinesis and Pollen Maturation in Arabidopsis Depend on TPLATE, Which Has Domains Similar to Coat Proteins". The Plant Cell. 18 (12): 3502–3518. doi:10.1105/tpc.106.040923. ISSN 1040-4651. PMC . PMID 17189342.
- Damme, Daniël Van; Rybel, Bert De; Gudesblat, Gustavo; Demidov, Dmitri; Grunewald, Wim; Smet, Ive De; Houben, Andreas; Beeckman, Tom; Russinova, Eugenia (2011-11-01). "Arabidopsis α Aurora Kinases Function in Formative Cell Division Plane Orientation". The Plant Cell. 23 (11): 4013–4024. doi:10.1105/tpc.111.089565. ISSN 1040-4651. PMC . PMID 22045917.