Pre-mitotic establishment of polarity is a key event in the preparation of mother cells for asymmetric cell divisions that produce daughters of distinct fates, and ensures correct cellular patterning of tissues and eventual organ function. Previous work has shown that two receptor-like kinases, PANGLOSS2 (PAN2) and PAN1, and the small GTPase RHO GTPASE OF PLANTS (ROP) promote mother cell polarity and subsequent division asymmetry in developing maize stomata. PAN proteins become polarized prior to asymmetric cell division, however, the mechanism of this polarization is unknown. Here we show that the SCAR/WAVE regulatory complex, which activates the actin-nucleating ARP2/3 complex, is the first known marker of polarity in this asymmetric division model and is required for PAN polarization. These findings implicate actin, and specifically branched actin networks, in PAN polarization and asymmetric cell division.
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We thank Kaiyue Deng for collecting complementation data in Supplementary Fig. 2 and the BICD101 class of 2009 at UC San Diego for sequencing brk3 alleles. This work was supported by NSF grants IOS-1147265 to LGS, NSF-1027446 to AWS, and a New Scholar Award from the Ellison Medical Foundation to EJB.
The authors declare no competing financial interests.
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