Department of Molecular and Structural Biochemistry, North Carolina State University, 128 Polk Hall, Raleigh, 27695, USA.
Sci Rep. 2018 Feb 12;8(1):2796. doi: 10.1038/s41598-018-21218-y.
During reproduction in flowering plants, the male gametophyte delivers an immotile male gamete to the female gametophyte in the pistil by formation of pollen tubes. In Arabidopsis thaliana, two synergid cells situated on either side of the egg cell produce cysteine-rich chemoattractant peptide LURE that guides the pollen tube to the female gametophyte for sexual reproduction. Recently, in Arabidopsis thaliana, Pollen Receptor Kinase 3 (PRK3), along with PRK1, PRK6, and PRK8, have been predicted to be the receptors responsible for sensing LURE. These receptors belong to the Leucine Rich Repeat Receptor Like Kinases (LRR-RLKs), the largest family of receptor kinases found in Arabidopsis thaliana. How PRKs regulate the growth and development of the pollen tube remains elusive. In order to better understand the PRK-mediated signaling mechanism in pollen tube growth and guidance, we have determined the crystal structure of the extracellular domain (ecd) of PRK3 at 2.5 Å, which resembles the SERK family of plant co-receptors. The structure of ecdPRK3 is composed of a conserved surface that coincides with the conserved receptor-binding surface of the SERK family of co-receptors. Our structural analyses of PRK3 have provided a template for future functional studies of the PRK family of LRR-RLK receptors in the regulation of pollen tube development.
在开花植物的繁殖过程中，雄性配子体通过花粉管的形成将不能运动的雄性配子输送到雌配子体的胚珠中。在拟南芥中，两个位于卵细胞两侧的助细胞产生富含半胱氨酸的趋化肽 LURE，引导花粉管向雌性配子体进行有性繁殖。最近，在拟南芥中，花粉受体激酶 3（PRK3）与 PRK1、PRK6 和 PRK8 一起被预测为感知 LURE 的受体。这些受体属于富含亮氨酸重复受体样激酶（LRR-RLKs），是拟南芥中发现的最大的受体激酶家族。PRKs 如何调节花粉管的生长和发育仍然难以捉摸。为了更好地理解 PRK 在花粉管生长和导向中的介导信号机制，我们已经确定了 PRK3 的细胞外结构域（ecd）在 2.5Å 的晶体结构，它类似于植物共受体的 SERK 家族。ecdPRK3 的结构由一个保守的表面组成，与 SERK 家族共受体的保守受体结合表面一致。我们对 PRK3 的结构分析为未来研究 PRK 家族的 LRR-RLK 受体在调节花粉管发育中的功能提供了一个模板。
