Moderate Drought Stress Induces Increased Foliar Dimethylsulphoniopropionate (DMSP) Concentration and Isoprene Emission in Two Contrasting Ecotypes of Arundo donax.

Matthew Haworth,Ezio Riggi,Marco Michelozzi,Mauro Centritto,Francesco Loreto,Giovanni Marino,Salvatore L. Cosentino,Giovanni Avola,Stefano Catola,Cecilia Brunetti

doi:10.3389/fpls.2017.01016

Abstract

The function of dimethylsulphoniopropionate (DMSP) in plants is unclear. It has been proposed as an antioxidant, osmolyte and overflow for excess energy under stress conditions. The formation of DMSP is part of the methionine (MET) pathway that is involved in plant stress responses. We used a new analytical approach to accurately quantify the changes in DMSP concentration that occurred in two ecotypes of the biomass crop Arundo donax subject to moderate drought stress under field conditions. The ecotypes of A. donax were from a hot semi-arid habitat in Morocco and a warm-humid environment in Central Italy. The Moroccan ecotype showed more pronounced reductions in photosynthesis, stomatal conductance and photochemical electron transport than the Italian ecotype. An increase in isoprene emission occurred in both ecotypes alongside enhanced foliar concentrations of DMSP, indicative of a protective function of these two metabolites in the amelioration of the deleterious effects of excess energy and oxidative stress. This is consistent with the modification of carbon within the methyl-erythritol and MET pathways responsible for increased synthesis of isoprene and DMSP under moderate drought. The results of this study indicate that DMSP is an important adaptive component of the stress response regulated via the MET pathway in A. donax. DMSP is likely a multifunctional molecule playing a number of roles in the response of A. donax to reduced water availability.

Highlights

Dimethylsulphoniopropionate (DMSP) is an important part of sulfur metabolism in photosynthetic organisms (Giovanelli, 1987; Stefels, 2000) and the precursor of the volatile organic compound (VOC) dimethyl sulphide (DMS) (Bentley and Chasteen, 2004)
Growth under rain-fed field conditions resulted in a reduced Relative Water Content (RWC) of A. donax leaves, but the difference in comparison with leaves of irrigated plots was not statistically significant (Figure 2)
The A. donax plants examined in this study showed no effect of drought on foliar RWC, and comparatively minor reductions in leaf gas exchange parameters in comparison to other studies (e.g., Cosentino et al, 2016; Haworth et al, 2017b); the drought stress experienced by the plants in this study was considered to be moderate for A. donax

Summary

Introduction

Dimethylsulphoniopropionate (DMSP) is an important part of sulfur metabolism in photosynthetic organisms (Giovanelli, 1987; Stefels, 2000) and the precursor of the volatile organic compound (VOC) dimethyl sulphide (DMS) (Bentley and Chasteen, 2004). Despite the central role played by DMSP in the global sulfur cycle, comparatively little is known about its role in plant growth or potential dynamics in response to plant stress. Previous analyses of DMSP have focused on marine phytoplankton and plants where it is found in higher concentrations. This has led to a hypothesis that DMSP formation competes with the emission of isoprene during stress (Dani and Loreto, 2017). If replicated in vascular plants, this would have major implications for our understanding of the regulation VOC emissions during stress. Analysis of DMSP in higher plants, under drought stress, has been neglected, and as a consequence the role of DMSP is unclear

Methods

Results

Discussion

Conclusion