Early Zinc Sensing and Signalling Events in Arabidopsis Roots, Upon Zn Starvation and Re-supply - ISRR 2018 10th Symposium for the International Society of Root Research

Borjana Arsova ¹ Sahand Amini ² Maxime Scheepers ² Dominique Baiwir ³ Gabriel Mazzucchelli ⁴ Monique Carnol ⁵ Bernard Bosman ⁵ Edwin de Pauw ⁴ Michelle Watt ¹ Marc Hanikenne ²

¹Root Dynamics Group, IBG-2 – Plant Sciences, Institut für Bio- und Geowissenschaften (IBG), Forschungszentrum Jülich, Germany
²InBioS-PhytoSystems, Dpt of Life Sciences, University of Liège, Belgium
³GIGA proteomics facility, University of Liège, Belgium
⁴Laboratory of Mass Spectrometry, MolSys Research Unit, University of Liège, Belgium
⁵Laboratory of Plant and Microbial Ecology, Department of Biology, Ecology, Evolution, University of Liège, Belgium

Zinc (Zn) is an essential micronutrient for many organisms, including plants and humans. Today 20% of the population suffers from Zn deficiency, a large part of which relies on plants for Zn uptake. Thus understanding plant Zn recognition mechanisms can lead to novel approaches of Zn biofortification in cereals and legumes. The approach presented here aimed to identify novel proteins in Zn sensing and signalling, by kick-starting the Zn signalling cascade on hydroponically grown Zn starved plants with Zn re-supply and profiling root and shoot proteins in a soluble and microsomal (membrane enriched) fraction. Proteomics and phosphoproteomics was performed after tightly controlled time-point sampling with focus on early times post re-supply, aiming to elucidate proteins involved in Zn triggered signalling cascades. In addition, transcript response was quantified by qRT-PCR, while ionomics was used for elemental analysis.

Results showed that in Arabidopsis, more than 2 hours passed from the first recognition of Zn by the root to the beginning of Zn accumulation in the shoot. Notably, in the root, the early signalling events were triggered at the cell membrane and very quickly became visible in proteins with predicted cytosolic and nuclear localization. Additionally preliminary results in protein phosphorylation uncovered finer mechanisms of protein post-translational modifications both in transporter and kinase levels. Significant transcript response was also visible in the first 10 minutes.

The dataset describes a number of previously unknown fluctuations in protein level during the time series, starting from ZIP transporters to newly identified proteins. To confirm the latter, we investigated the response of around 30 genes using 40 T-DNA insertion lines on Zn deficiency or Zn toxicity and quantified the phenotype in planta. This approach is being followed with a confirmation in the cereal model Brachypodium to help identify potential breeding targets in the family Poaceae.