Ascophyllum nodosum Seaweed Extract Alleviates Drought Stress in Arabidopsis by Affecting Photosynthetic Performance and Related Gene Expression.

Antonietta Santaniello,Pierdomenico Perata,Donatella Di Tommaso,Alessandro Biasone,Francesco Gresta,Elena Loreti,Andrea Scartazza,Alberto Piaggesi

doi:10.3389/fpls.2017.01362

Abstract

Drought represents one of the most relevant abiotic stress affecting growth and yield of crop plants. In order to improve the agricultural productivity within the limited water and land resources, it is mandatory to increase crop yields in presence of unfavorable environmental stresses. The use of biostimulants, often containing seaweed extracts, represents one of the options for farmers willing to alleviate abiotic stress consequences on crops. In this work, we investigated the responses of Arabidopsis plants treated with an extract from the brown alga Ascophyllum nodosum (ANE), under drought stress conditions, demonstrating that ANE positively influences Arabidopsis survival. Pre-treatment with ANE induced a partial stomatal closure, associated with changes in the expression levels of genes involved in ABA-responsive and antioxidant system pathways. The pre-activation of these pathways results in a stronger ability of ANE-treated plants to maintain a better photosynthetic performance compared to untreated plants throughout the dehydration period, combined with a higher capacity to dissipate the excess of energy as heat in the reaction centers of photosystem II. Our results suggest that drought stressed plants treated with ANE are able to maintain a strong stomatal control and relatively higher values of both water use efficiency (WUE) and mesophyll conductance during the last phase of dehydration. Simultaneously, the activation of a pre-induced antioxidant defense system, in combination with a more efficient energy dissipation mechanism, prevents irreversible damages to the photosynthetic apparatus. In conclusion, pre-treatment with ANE is effective to acclimate plants to the incoming stress, promoting an increased WUE and dehydration tolerance.

Highlights

The consumption of water by human is mainly driven by the activities aimed at food production, since irrigated agriculture is extremely important for global food provision
We tested the effects of a pre-treatment with Ascophyllum nodosum extract (ANE) on Arabidopsis tolerance to drought stress (Figure 1A)
Plants treated for 5 days with ANE did not show phenotypical differences compared to untreated ones, but they were significantly different in terms of drought tolerance

Summary

Introduction

The consumption of water by human is mainly driven by the activities aimed at food production, since irrigated agriculture is extremely important for global food provision. Drought is defined as one of the most limiting factors for plant growth and yield, which causes changes at molecular and physiological level These changes vary from morphology to the expression of genes and include stomatal response, metabolic adjustments and changes in photosynthesis rate (Chaves, 1991; Chaves et al, 2009). High levels of ROS in the cell result in extensive damage to DNA, proteins and lipids, causing a metabolic dysfunction which leads to plant death (Gill and Tuteja, 2010; Anjum, 2015) To prevent these permanent damages to the photosynthetic apparatus, plants evolved efficient and complex protective mechanisms, for triggering adaptive responses. Non-enzymatic antioxidant mechanisms involve low molecular weight compounds, such as ascorbic acid, reduced glutathione, flavonoids, and carotenoids (Foyer and Noctor, 2005; Gill and Tuteja, 2010)

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