Update on signaling pathways regulating polarized intercellular communication in Arabidopsis reproduction
Update on signaling pathways regulating polarized intercellular communication in Arabidopsis reproduction
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DOI：
10.1093/plphys/kiad414
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发表时间：
2023-10-26
期刊：
影响因子：
7.4
通讯作者：
Kessler, Sharon A.
中科院分区：
文献类型：
--
作者：
Ogawa, Sienna T.;Kessler, Sharon A.
细胞极性是指细胞内细胞成分、结构和功能的不对称分布。植物细胞极性的大多数例子涉及单个细胞或细胞群，它们通过细胞壁与相邻细胞相连。开花植物的繁殖是独特的，因为它涉及高度极化的细胞之间的细胞间信号传导，尖端生长的花粉管，必须通过雌蕊的各种孢子体组织找到胚珠并将其精子细胞货物运送到雌蕊深处的雌性配子，在那里发生双受精以形成下一代（约翰逊等人。2019）。花粉管的旅程涉及到一系列的细胞极性变化，在短时间内发生在单细胞中，以响应来自另一种细胞类型的信号。如果花粉来自不同的植物，这些相互作用发生在具有不同倍性和潜在不同基因型的细胞之间。单倍体雄配子体或花粉粒在花药中形成，是减数分裂的产物，随后进行2轮有丝分裂，形成具有2个嵌入的精细胞的营养细胞（图1）（Hafidh和Honys 2021）。在大多数被子植物中，单倍体雌性配子体（也称为胚囊）形成于胚珠中，是减数分裂的产物，随后经过3轮有丝分裂形成7细胞结构，包含2个配子、卵细胞和中央细胞，以及称为助细胞和反足细胞的辅助细胞（图1）（Hater et al. 2020）。授粉的目标是将雄配子体中的2个精细胞输送到雌配子体中的2个配子中，以进行双受精（约翰逊等人，2019）。这一目标需要花粉粒与二倍体孢子体柱头乳突细胞之间的相互作用，然后是顶端生长的花粉管与柱头、花柱、传递道、隔膜和珠柄的孢子体细胞之间的相互作用（图1）。最后，花粉管与雌配子体的高度极化的单倍体助细胞相互作用，并获得释放精细胞的信号，从而与卵和中央细胞发生极性相互作用。不同细胞类型之间的这些相互作用导致顶端生长的花粉管响应于来自母体孢子体和配子体细胞的极性信号而改变极性和生长方向。(See图1为花粉管顶端生长的概况。在这些细胞间通讯事件中反复出现的主题是通过极性定位的受体样激酶（RLKs）感知肽配体，从而导致快速的细胞事件。在植物生殖的几个阶段，CrRLK1L家族的马来凝集素样RLK对快速碱化因子（RALF）或从不同细胞类型（旁分泌信号传导）或从相同细胞（自分泌信号传导）分泌的其他肽配体产生应答，以触发调节花粉管生长方向和完整性的信号转导级联（Zhu et al. 2021）。在这次更新中，我们将讨论在理解植物繁殖过程中的极化花粉管生长和细胞间信号传导的调节方面的最新进展，重点是模式植物拟南芥（Arabidopsis thaliana）的研究。
Cell polarity refers to the asymmetric distribution of cellular components, structure, and function within a cell. Most instances of cell polarity in plants involve single cells or groups of cells that are attached to neighboring cells by the cell wall. Flowering plant reproduction is unique because it involves intercellular signaling between a highly polarized cell, the tip-growing pollen tube, that must navigate its way through various sporophytic tissues of the pistil to find the ovules and deliver its sperm cell cargo to the female gametes deep within the pistil where double fertilization occurs to form the next generation (Johnson et al. 2019). The pollen tube’s journey involves a series of cell polarity changes in single cells occurring over short time periods in response to signals from another cell type. These interactions occur between cells that have different ploidy and potentially different genotypes if the pollen comes from a different plant. The haploid male gametophyte, or pollen grain, is formed in the anther and is the product of meiosis followed by 2 rounds of mitosis to form the vegetative cell with 2 embedded sperm cells (Fig. 1)(Hafidh and Honys 2021). In most angiosperms, the haploid female gametophyte, also known as the embryo sac, is formed in the ovule and is the product of meiosis followed by 3 rounds of mitosis to form a 7-celled structure that contains 2 gametes, the egg and central cell, and accessory cells known as the synergids and antipodal cells (Fig. 1)(Hater et al. 2020). The goal of pollination is to deliver the 2 sperm cells from the male gametophyte to the 2 gametes in the female gametophyte for double fertilization (Johnson et al. 2019). This goal requires interactions between the pollen grain and a diploid, sporophytic stigma papilla cell, followed by interactions between the tip-growing pollen tube and the sporophytic cells of the stigma, style, transmitting tract, septum, and funiculus (Fig. 1). Finally, the pollen tube interacts with the highly polarized haploid synergid cells of the female gametophyte and gets the signal to release the sperm cells so that polar interactions can occur with the egg and central cell. These interactions between the different cell types result in changes in polarity and growth direction of the tip-growing pollen tube in response to polar signals from the maternal sporophytic and gametophytic cells.(See Box 1 for an overview of tip growth in pollen tubes.) A recurrent theme in these intercellular communication events is the perception of peptide ligands by polarly localized receptor-like kinases (RLKs) leading to rapid cellular events. At several stages of plant reproduction, the CrRLK1L family of malectin-like RLKs respond to RAPID ALKALINIZATION FACTOR (RALF) or other peptide ligands secreted from a different cell type (paracrine signaling) or from the same cell (autocrine signaling) to trigger signal transduction cascades that regulate pollen tube growth direction and integrity (Zhu et al. 2021). In this Update, we will discuss the latest advances in understanding the regulation of polarized pollen tube growth and intercellular signaling during plant reproduction, with an emphasis on research from the model plant Arabidopsis (Arabidopsis thaliana).