In vivo gibberellin gradients visualized in rapidly elongating tissues

Abstract

The phytohormone gibberellin (GA) is a key regulator of plant growth and development. Although the upstream regulation and downstream responses to GA vary across cells and tissues, developmental stages and environmental conditions, the spatiotemporal distribution of GA in vivo remains unclear. Using a combinatorial screen in yeast, we engineered an optogenetic biosensor, GIBBERELLIN PERCEPTION SENSOR 1 (GPS1), that senses nanomolar levels of bioactive GAs. Arabidopsis thaliana plants expressing a nuclear localized GPS1 report on GAs at the cellular level. GA gradients were correlated with gradients of cell length in rapidly elongating roots and dark-grown hypocotyls. In roots, accumulation of exogenously applied GA also correlated with cell length, intimating that a root GA gradient can be established independently of GA biosynthesis. In hypocotyls, GA levels were reduced in a phytochrome interacting factor (pif) quadruple mutant in the dark and increased in a phytochrome double mutant in the light, indicating that PIFs elevate GA in the dark and that phytochrome inhibition of PIFs could lower GA in the light. As GA signalling directs hypocotyl elongation largely through promoting PIF activity, PIF promotion of GA accumulation represents a positive feedback loop within the molecular framework driving rapid hypocotyl growth.

Mitochondrial Energy Signaling and Its Role in the Low-Oxygen Stress Response of Plants

“…Multiplexing approaches will resolve the order of events and help to dissect cause from coincidence as well as the interconnectivity of the physiological network that feeds into the signaling network through specific messengers. Recent in vivo sensing approaches have unearthed first links between membrane potential, pH, Ca 2+ , ABA, and GA, although more than two or three parameters have rarely been assessed at a time (Schwarzländer et al, 2012b;Rizza et al, 2017;Waadt et al, 2017). Breaking those limitations and driving sensor multiplexing toward the omics scale of small molecular signal candidates would enable us to get direct and specific fingerprints of any transition, may it be a stress stimulus or the effect of a specific inhibitor.…”

A Sizer model for cell differentiation in Arabidopsis thaliana root growth

“…Such a molecular mechanism could fit with a Sizer mechanism, since the level of gibberellin signaling is thus dependent on the length of the cell. However, the recent visualization of gibberellins suggests another type of gradient (Rizza et al , ). Third, across natural variation, the length of the mature cell in the root exhibits a correlation with the length of the meristem (Meijón et al , ), suggesting a possible dependence of these elements and a Ruler type of mechanism to set the EZ.…”

Seeing is better than believing: visualization of membrane transport in plants

“…Both sensors have proven to be useful in demonstrating kinetics of ABA transport and dynamics upon application of external ABA, [30,32,59 ]. The nuclear localized GA sensor, GIBBERELLIN PER-CEPTION SENSOR 1 (GPS1), allowed sensing of nanomolar concentrations in Arabidopsis [61].…”