School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK.
Complex Carbohydrate Research Center, University of Georgia, Athens, GA, 30602-4712, USA.
New Phytol. 2018 Jan;217(2):491-500. doi: 10.1111/nph.14845. Epub 2017 Oct 9.
Occam's Razor suggests a new model of pollen tube tip growth based on a novel Hechtian oscillator that integrates a periplasmic arabinogalactan glycoprotein-calcium (AGP-Ca ) capacitor with tip-localized AGPs as the source of tip-focussed cytosolic Ca oscillations: Hechtian adhesion between the plasma membrane and the cell wall of the growing tip acts as a piconewton force transducer that couples the internal stress of a rapidly growing wall to the plasma membrane. Such Hechtian transduction opens stretch-activated Ca channels and activates H -ATPase proton pump efflux that dissociates periplasmic AGP-Ca resulting in a Ca influx that activates exocytosis of wall precursors. Thus, a highly simplified pectic primary cell wall regulates its own synthesis by a Hechtian growth oscillator that regulates overall tip growth. By analogy with the three cryptic inscriptions of the classical Rosetta Stone, the Hechtian Hypothesis translates classical AGP function as a Ca capacitor, pollen tube guide and wall plasticizer into a simple but widely applicable model of tip growth. Even wider ramifications of the Hechtian oscillator may implicate AGPs in osmosensing or gravisensing and other tropisms, leading us yet further towards the Holy Grail of plant growth.
奥卡姆剃刀原理提出了一种新的花粉管尖端生长模型,该模型基于一种新型的赫希氏振荡器,该振荡器将质外体阿拉伯半乳糖蛋白-钙(AGP-Ca)电容器与局部化的 AGP 整合在一起,作为尖端聚焦的胞质 Ca 振荡的来源:质膜和生长尖端细胞壁之间的赫希氏黏附作为皮牛顿力传感器,将快速生长壁的内部应力与质膜耦合。这种赫希氏转导打开了伸展激活的 Ca 通道,并激活 H -ATPase 质子泵外排,使质外 AGP-Ca 解离,导致壁前体的胞吐作用。因此,高度简化的果胶初生细胞壁通过调节自身合成的赫希氏生长振荡器来调节整体尖端生长。通过类比经典罗塞塔石碑的三个隐藏铭文,赫希氏假设将经典的 AGP 功能翻译为 Ca 电容器、花粉管导向和壁塑化剂,转化为一种简单但广泛适用的尖端生长模型。赫希氏振荡器的更广泛影响可能会使 AGP 参与渗透感应或重力学感应和其他向性,使我们进一步接近植物生长的圣杯。