How do growth hormones interact to specify female-germline cell types in flowering plants and control production of the first female-germline cell? Here, we find that gibberellin (GA) biosynthesis and signaling are restricted in ovule primordia, with overexpression of receptors and biosynthetic enzymes resulting in multiple and enlarged megaspore mother cells (MMCs) in Arabidopsis. GA signaling machinery interacts with and promotes the degradation of cytokinin (CK) type-B Arabidopsis response regulators (ARR1/10/12), which also directly interact with DELLA proteins. CK biosynthesis and signaling components are expressed in both MMCs and sporophytic cells, with signaling negatively controlled by GA in ovule primordia, and perturbations leading to the induction of multiple, enlarged MMC-like cells. The vacuolar sorting protein SHRUBBY (SHBY) interacts with GA and CK signaling components to block GA-induced degradation. CK signaling restricts multiple sub-epidermal cells in distal ovule primordia from acquiring MMC identity. By balancing degradation activity, GA and CK signaling antagonistically control female-germline cell specification.

中文翻译：

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赤霉素和细胞分裂素信号转导拮抗控制拟南芥中的雌性生殖细胞规格


生长激素如何相互作用以指定开花植物中的雌性种系细胞类型并控制第一个雌性种系细胞的产生？在这里，我们发现赤霉素 （GA） 生物合成和信号在胚珠原基中受到限制，受体和生物合成酶的过表达导致拟南芥中多个和扩大的大孢子母细胞 （MMC）。GA 信号转导机制与细胞分裂素 （CK） B 型拟南芥反应调节因子 （ARR1/10/12） 相互作用并促进其降解，后者也直接与 DELLA 蛋白相互作用。CK 生物合成和信号转导组分在 MMC 和孢子体细胞中均表达，信号转导受胚珠原基中 GA 的负控制，扰动导致诱导多个增大的 MMC 样细胞。液泡分选蛋白 SHRUBBY （SHBY） 与 GA 和 CK 信号转导组分相互作用，以阻断 GA 诱导的降解。CK 信号转导限制远端胚珠原基中的多个表皮下细胞获得 MMC 身份。通过平衡降解活性，GA 和 CK 信号转导拮抗控制女性生殖细胞的规格。