Although plants do not have a nerve system, they are capable of detecting and responding to environmental changes. In fact, many of such signaling mechanisms are highly conserved at the molecular level in plants and animals. One good example is that both plants and animals utilize calcium ion (Ca2+) as a universal signal in response to myriad of stimuli. A fundamental question is how Ca2+, a simple cation, encodes complex information with high specificity. Extensive research has established a two-step process (coding and decoding) that governs the specificity of Ca2+ signals. While the coding mechanism entails a complex array of channels and transporters, the decoding process features a number of Ca2+ sensors and effectors that convert Ca2+ signals into cellular effects. Along this general paradigm, some signaling components may be highly conserved, but others divergent among different organisms. In plant cells, Ca2+ participates in numerous signaling processes and here I focus on the latest discoveries we have made on Ca2+-encoding mechanisms in development and defense. In particular, we use examples such as polarized cell growth of pollen tube and root hair in which tip-focused Ca2+ oscillations specify the signaling events for rapid cell elongation (just like in animal axon guidance and fungal hyphae growth). In plant-microbe interaction, like human immune response, Ca2+ spiking and oscillations hold the key to signaling specificity. Herbivore attack or mechanical wounding can trigger Ca2+ waves traveling a long distance to transmit and convert the local signal to a systemic defense program in the whole plant (reminiscent to animal synaptic transmission). The future work will further expand the toolkit for Ca2+ encoding mechanisms and place the Ca2+ signaling steps into the larger signaling networks.
Professor Sheng Luan is Associate Chair of the Department of Plant and Microbial Biology at the University of California Berkeley. Prof Luan received his PhD in Cell and Developmental Biology at Harvard University, and continued his postdoctoral training there. He joined UC Berkeley in 1995 and became a full professor in 2004. His current research looks at calcium signalling mechanisms in plants. He has published more than 150 research and review articles in premier journals including Annual Review of Plant Biology, Trends in Plant Sciences, PNAS, Nature and Science Signaling, among many others. Prof Luan received numerous awards including the Charles Albert Shull Award and the Alexander von Humboldt Prize. He is a Fellow of AAAS and a Fellow of the American Society of Plant Biologists. He was selected as Web of Science “Highly Cited Researcher” in 2014, 2015, 2016 and 2018. Prof Luan is the founding Editor-in-Chief of Molecular Plant, a leading plant biology journal published by Cell Press.