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. 2022 Dec 20;11:e79913. doi: 10.7554/eLife.79913

Figure 6. A mechanistic model of subsidiary mother cell (SMC) polarisation by the two oppositely polarised BdPOLAR and BdPAN1 domains.

Figure 6.

(A) Stages of subsidiary cell (SC) development. (1) SMC identity is established by BdMUTE and BdPAN1 polarises at the guard mother cell (GMC)/SMC interface independent of SMC establishment. (2) BdPOLAR is strongly expressed in SMCs and localises at the apical, basal, and distal plasma membrane (PM) of SMCs and is excluded from the BdPAN1 domain. The SMC nucleus migrates towards the GMC/SMC interface, and the cortical division sites are established above and below the GMC/SMC interface. (3) An asymmetric cell division generates a smaller SC and a larger pavement cell. BdPOLAR quickly dissociates from the PM and reorients towards the newly formed PM. (B) Cellular mechanisms of BdPAN1 and BdPOLAR in pre-mitotic SMCs. BdPAN1 guides the migration of the SMC nucleus towards its own domain. BdPAN1 actively inhibits BdPOLAR from entering its domain, either biochemically or by steric hindrance. Distal BdPOLAR prevents cortical division site factors from ectopically binding and forces it to form specifically where BdPOLAR protein level is low.