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. 2020 Aug 31;39(19):e105802. doi: 10.15252/embj.2020105802

Figure 4. Role of Arabidopsis RBR1 in stem cell maintenance and asymmetric cell division.

Figure 4

(A) In the stem cell niche of the RAM, the cortex–endodermis initial derivative (CEID) cell undergoes an asymmetric cell division (ACD) that renders the initials of endodermis and cortex already having different fates. This ACD depends on CDK/CYCD6;1, the latter a target of the SHR/SCR heterodimer. The negative regulation of SCR by RBR1 is counteracted by RBR1 phosphorylation. (B) In the stomatal lineage, RBR1 also plays multiple roles including restriction of excessive proliferation of stem cells and the symmetric division of GMC to produce the young guard cells (GCs) as well as the terminal differentiation of GCs into mature guard cells of the stoma. This occurs by association with FAMA and polycomb repressor complex 2 (PRC2). The participation of FLP‐RBR1 in terminal differentiation of GCs is also shown. The three major transcription factors acting in the stomatal lineage, SPCH, MUTE, and FAMA, are shown highlighting their functional windows.