Date: 18th January 2023
Time: 13:00
Title: Bringing into focus the cellular dynamics of plant hormones using fluorescent biosensors and optogenetics
Location: Lecture room B6, Forest Sciences Building, Latokartanonkaari 7-9 and remotely via Zoom
Host: Timo Hytönen
Abstract: How do multicellular organisms solve the challenge of coordinating signals across cells, tissues and organs to respond to environmental stresses. A big part of the answer lies in hormones. In animals, these are often produced in special glands and target specific cell types, but in plants they are produced by a much wider range of cells and can target many cell types. With such distributed ‘decision making’, how do specific and appropriate responses to these mobile small molecules arise? Our view is that internal signals and external cues encode information in cellular hormone dynamics, and then spatiotemporally specific hormone signalling processes this information to activate appropriate downstream responses. In order to visualize these crucial cellular hormone dynamics, we develop high-resolution fluorescent biosensors. Gibberellin Perception Sensors (GPS1, GPS2) are FRET based biosensors that we use to unravel how cellular GA dynamics are determined as well as which aspects of these cellular GA dynamics are functionally relevant for root growth, apical hook development, and root symbioses. We also recently developed FRET biosensors for other important plant hormones. For example, next-generation Abscisic Acid Concentration and Uptake Sensor 2s (ABACUS2s) provide unprecedented resolution in our understanding of cellular ABA dynamics and allowed us to detect inter-organ growth coordination in response to humidity fluctuations. Additional hormone sensors still in development as well as a novel optogenetic gene expression switch for plants will also be discussed.
Plant hormones in action
The Jones team at the Sainsbury Laboratory Cambridge University (SLCU) is fascinated by how plants respond to the world. Stems and leaves grow towards light, whilst their roots grow towards water and nutrients. Some plants reproduce when triggered by stimuli such as warmth and day length. They reprogram their physiology when water is scarce and activate antimicrobial immune systems when they are being attacked by pathogens. Yet plants do not have a nervous system, a brain, or any of the sensory organs that we are familiar with in animals – so how do they know how to respond?
Cellular hormone dynamics
A big part of the answer lies in plant hormones. The term ‘hormone’ can simply refer to a chemical that acts as a ‘messenger’ within an organism, often travelling from one place to another to tell a particular cell what to do. In animals, these are often produced in special glands and target specific cell types, but in plants they are produced by a much wider range of cells and can target many cell types. With such distributed ‘decision making’, how do specific and appropriate responses to these mobile small molecules arise? Our view is that internal signals and external cues encode information in cellular hormone dynamics, and then cellular hormone signalling processes this information to activate appropriate downstream responses. For instance, production of the plant hormone gibberellin (GA) can be triggered by cues like decreased light, increased temperature or salt stress. GA levels also fluctuate depending on internal cues, such as the stage at which the plant is in its lifecycle. Once GA accumulates to a certain level, it can trigger growth programmes. The exact nature of the growth that follows depends on the GA concentration, the plant tissue, and the timing.
The Jones group aims to map spatiotemporal hormone patterns at high-resolution in vivo and then reveal how specific hormone dynamics connect upstream cues and signals with downstream programmes relevant to development.