Multicellular development depends on generating and precisely positioning distinct cell types within tissues. During leaf development, pores in the epidermis called stomata are spaced at least one cell apart for optimal gas exchange. This pattern is primarily driven by iterative asymmetric cell divisions (ACDs) in stomatal progenitors, which generate most of the cells in the tissue. A plasma membrane-associated polarity crescent defined by BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE (BASL) and BREVIS RADIX family (BRXf) proteins is required for asymmetric divisions and proper stomatal pattern, but the cellular mechanisms that orient ACDs remain unclear. Here, utilizing long-term, quantitative time-lapse microscopy, we identified two oppositely oriented nuclear migrations that precede and succeed ACD during epidermal patterning. The pre- and post-division migrations are dependent on microtubules and actin, respectively, and the polarity crescent is the unifying landmark that is both necessary and sufficient to orient both nuclear migrations. We identified a specific and essential role for MYOXI-I in controlling post-ACD nuclear migration. Loss of MYOXI-I decreases stomatal density, owing to an inability to accurately orient a specific subset of ACDs. Taken together, our analyses revealed successive and polarity-driven nuclear migrations that regulate ACD orientation in the Arabidopsis stomatal lineage.

多细胞发育依赖于在组织内生成和精确定位不同的细胞类型。在叶片发育过程中，表皮中称为气孔的孔至少间隔一个细胞，以实现最佳的气体交换。这种模式主要是由气孔祖细胞中的迭代不对称细胞分裂 (ACD) 驱动的，气孔祖细胞在组织中产生大部分细胞。由气孔谱系 (BASL) 和 BREVIS RADIX 家族 (BRXf) 蛋白的不对称定义定义的质膜相关极性新月体是不对称分裂和适当气孔模式所必需的，但定向 ACD 的细胞机制仍不清楚。在这里，利用长期、定量延时显微镜，我们确定了两个相反方向的核迁移，它们在表皮图案形成过程中发生在 ACD 之前和之后。分裂前和分裂后的迁移分别依赖于微管和肌动蛋白，而极性新月形是统一的地标，它对于引导两种核迁移都是必要和充分的。我们确定了 MYOXI-I 在控制 ACD 后核迁移中的特定和重要作用。由于无法准确定位 ACD 的特定子集，MYOXI-I 的缺失会降低气孔密度。总之，我们的分析揭示了连续的和极性驱动的核迁移，这些迁移在 由于无法准确定位 ACD 的特定子集，MYOXI-I 的缺失会降低气孔密度。总之，我们的分析揭示了连续的和极性驱动的核迁移，这些迁移在 由于无法准确定位 ACD 的特定子集，MYOXI-I 的缺失会降低气孔密度。总之，我们的分析揭示了连续的和极性驱动的核迁移，这些迁移在拟南芥气孔谱系。