TREE CAPACITANCE

Insights into the ecophysiological and molecular significance of xylem hydraulic capacitance in Populus under drought stress

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 Obiettivo del progetto (Objective)

'Global change is expected to amplify the frequency and the severity of heatwaves and drought events especially in Western Europe. These droughts jeopardize tree health and integrity of European temperate forests and tied ecosystems. There is a need to identify the processes that may allow trees to overcome severe water scarcities. Tolerance to xylem embolism is an intrinsic and operational trait related to tree drought resistance. Moreover, ecophysiological studies have pointed to the existence of hydraulic capacitance connected to embolism as a preventive way out against moderate desiccation avoidances and buffering water potential fluctuations. This capacitance influence is expected to be ensured by living xylem elements (capacitors). However, capacitance is paradoxically a rare physiological event underlined, as the physical and genetic basis of capacitance remain totally unresolved. Here the aim of the project is to define the “hydraulic capacity” of xylem capacitor elements under quantified changes in xylem water tension state, and to identify a class of genes placed alongside physiological and biochemical measurements that will highlight the functioning of these capacitors. To achieve this task, our strategy will be first to identify the key ecophysiological features of xylem capacitance and secondly, we will undertake a molecular study to correlate the potential involvement of genes (WAK and MIP) coding for this process. Lastly, we will perform the functional validation of related proteins of interest by biochemical and bioinformatic approaches. This tree hydraulic capacitance project fits perfectly into the framework of Marie Curie Actions, spanning the “Environmental and Geo-Sciences” and “Life Sciences” themes. As the underlying nature involving drought adaptive responses using cell water capacitance may be common to all living organisms, this project can expect to contribute to this growing pool of knowledge and skilled researchers in the ERA.'

Introduzione (Teaser)

New research has revealed specific genes and proteins that help trees protect themselves against drought stress.

Descrizione progetto (Article)

Forests in western Europe are particularly vulnerable to drought events and heat waves, which are becoming more frequent and severe. Trees can, however, defend against extreme water scarcities using hydraulic capacitance within xylem (vessels that transport water from the roots through the rest of the plant).

The precise physical and genetic mechanisms of this hydraulic capacitance process have remained unclear, but the EU-funded TREE CAPACITANCE project gained new insights. Using several hybrid and control poplars, researchers were able to unravel the physical mechanisms of capacitance during water deprivation and normal conditions.

They also determined that two genes, aquaporins (AQPs) and wall-associated kinases (WAKs), are differentially regulated under changing plant water status. AQPs code for water channel proteins, while WAKs code for proteins that are bound to the cell wall and to the plasma membrane.

These findings support the hypothesis that WAKs can sense dehydration and then regulate the activity of aquaporins accordingly.

TREE CAPACITANCE researchers thus shed new light on how the hydraulic capacity of xylem water reservoirs buffers the effects of drought stress in trees. This research will support European forest production and environmental protection efforts in the face of climate change.