Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA, USA.
School of Life Sciences, Northwest University, Xi'an, China.
Nat Plants. 2020 Jul;6(7):750-759. doi: 10.1038/s41477-020-0667-6. Epub 2020 Jun 29.
The calcium ion (Ca) is a universal signal in all eukaryotic cells. A fundamental question is how Ca, a simple cation, encodes complex information with high specificity. Extensive research has established a two-step process (encoding and decoding) that governs the specificity of Ca signals. While the encoding mechanism entails a complex array of channels and transporters, the decoding process features a number of Ca sensors and effectors that convert Ca signals into cellular effects. Along this general paradigm, some signalling components may be highly conserved, but others are divergent among different organisms. In plant cells, Ca participates in numerous signalling processes, and here we focus on the latest discoveries on Ca-encoding mechanisms in development and biotic interactions. In particular, we use examples such as polarized cell growth of pollen tube and root hair in which tip-focused Ca oscillations specify the signalling events for rapid cell elongation. In plant-microbe interactions, Ca spiking and oscillations hold the key to signalling specificity: while pathogens elicit cytoplasmic spiking, symbiotic microorganisms trigger nuclear Ca oscillations. Herbivore attacks or mechanical wounding can trigger Ca waves traveling a long distance to transmit and convert the local signal to a systemic defence program in the whole plant. What channels and transporters work together to carve out the spatial and temporal patterns of the Ca fluctuations? This question has remained enigmatic for decades until recent studies uncovered Ca channels that orchestrate specific Ca signatures in each of these processes. Future work will further expand the toolkit for Ca-encoding mechanisms and place Ca signalling steps into larger signalling networks.
钙离子（Ca）是所有真核细胞中的通用信号。一个基本问题是，作为一种简单的阳离子，Ca 如何以高度特异性编码复杂信息。大量研究已经建立了一个两步过程（编码和解码）来控制 Ca 信号的特异性。虽然编码机制涉及到复杂的通道和转运蛋白阵列，但解码过程具有许多 Ca 传感器和效应器，可将 Ca 信号转化为细胞效应。沿着这个一般范式，一些信号成分可能高度保守，但其他成分在不同生物体中是不同的。在植物细胞中，Ca 参与了许多信号过程，我们在这里重点介绍关于 Ca 编码机制在发育和生物相互作用中的最新发现。特别是，我们使用花粉管和根毛的极化细胞生长等例子，其中尖端聚焦的 Ca 振荡指定了快速细胞伸长的信号事件。在植物-微生物相互作用中，Ca 爆发和振荡是信号特异性的关键：病原体引发细胞质爆发，共生微生物引发核 Ca 振荡。食草动物的攻击或机械创伤会引发 Ca 波，在整个植物中远距离传播并将局部信号转换为系统防御程序。哪些通道和转运蛋白一起形成 Ca 波动的时空模式？这个问题几十年来一直是个谜，直到最近的研究揭示了在这些过程中的每一个过程中协调特定 Ca 特征的 Ca 通道。未来的工作将进一步扩展 Ca 编码机制的工具包，并将 Ca 信号步骤纳入更大的信号网络中。
