Priming with a Seaweed Extract Strongly Improves Drought Tolerance in Arabidopsis

Abstract

Drought represents a major threat to plants in natural ecosystems and agricultural settings. The biostimulant Super Fifty (SF), produced from the brown alga Ascophyllum nodosum, enables ecologically friendly stress mitigation. We investigated the physiological and whole-genome transcriptome responses of Arabidopsis thaliana to drought stress after a treatment with SF. SF strongly decreased drought-induced damage. Accumulation of reactive oxygen species (ROS), which typically stifle plant growth during drought, was reduced in SF-primed plants. Relative water content remained high in SF-treated plants, whilst ion leakage, a measure of cell damage, was reduced compared to controls. Plant growth requires a functional shoot apical meristem (SAM). Expression of a stress-responsive negative growth regulator, RESPONSIVE TO DESICCATION 26 (RD26), was repressed by SF treatment at the SAM, consistent with the model that SF priming maintains the function of the SAM during drought stress. Accordingly, expression of the cell cycle marker gene HISTONE H4 (HIS4) was maintained at the SAMs of SF-primed plants, revealing active cell cycle progression after SF priming during drought. In accordance with this, CYCP2;1, which promotes meristem cell division, was repressed by drought but enhanced by SF. SF also positively affected stomatal behavior to support the tolerance to drought stress. Collectively, our data show that SF priming mitigates multiple cellular processes that otherwise impair plant growth under drought stress, thereby providing a knowledge basis for future research on crops.

Recent Advances in the Molecular Effects of Biostimulants in Plants: An Overview

“…Priming and foliar application with SuperFifty led to a better tolerance against drought stress in Arabidopsis thaliana, with primed plants showing better development than control plants. Moreover, electrolyte leakage was observed to decrease in treated plants, and the reduction in relative water content (RWC) and ROS accumulation due to drought were shown to be diminished [137]. More interestingly, plants primed with this SWE displayed a substantial amount of differently expressed genes, suppressing those with negative effects such as ROS accumulation and upregulating those with positive effects such as ROS scavengers.…”

“…It has been suggested that non-growth hormone components in seaweed, such as polysaccharides, may be responsible for growth enhancing effects induced by SWE [132,133]. Polysaccharides are major components of brown seaweeds [134], and recent studies show that a particular commercial Ascophyllum nodosum (Super Fifty) extract high in polysaccharides modulates a range of processes at the transcriptomic, metabolic and lipid levels [135][136][137]. The authors demonstrate that these changes involve multiple pathways and culminate in significant changes at the phenotypic level, including: tolerance to oxidative stress and abiotic stresses; reductions in Reactive Oxygen Species (ROS); reductions in electrolyte leakage and increases in plant growth.…”

“…More interestingly, plants primed with this SWE displayed a substantial amount of differently expressed genes, suppressing those with negative effects such as ROS accumulation and upregulating those with positive effects such as ROS scavengers. Stress responsive negative regulator of growth, RESPONSIVE TO DESICCATION 26 (RD 26) was repressed and cell cycle genes were activated in shoot apical meristems of SWE primed plants, revealing an active cell division and growth taking place in these plants during drought [137]. Priming with A. nodosum extracts (SuperFifty and Rygex) also induced pre-adaptive physiological responses, improved yield and reallocated the biomass towards the fruits in tomato plants during salt stress [154].…”

A Seaweed Extract-Based Biostimulant Mitigates Drought Stress in Sugarcane

“…The decreases in glucose, fructose, and fiber levels resulted in higher total recoverable sugar (TRS). Other studies have also reported a strong influence of polysaccharides that are abundant in various seaweed extracts, including those from A. nodosum , on vegetative parameters ( Craigie, 2010 ; Omidbakhshfard et al, 2020 ; Baltazar et al, 2021 ; Rasul et al, 2021 ). These non-growth hormone compounds modulate metabolic, lipid, and transcription pathways to promote phenotypic changes in plants that facilitate growth, such as improved resistance to stress, reduced ROS levels, and decreased electrolyte loss due to cell damage ( Craigie, 2010 ; Omidbakhshfard et al, 2020 ; Baltazar et al, 2021 ; Rasul et al, 2021 ).…”

“…Other studies have also reported a strong influence of polysaccharides that are abundant in various seaweed extracts, including those from A. nodosum , on vegetative parameters ( Craigie, 2010 ; Omidbakhshfard et al, 2020 ; Baltazar et al, 2021 ; Rasul et al, 2021 ). These non-growth hormone compounds modulate metabolic, lipid, and transcription pathways to promote phenotypic changes in plants that facilitate growth, such as improved resistance to stress, reduced ROS levels, and decreased electrolyte loss due to cell damage ( Craigie, 2010 ; Omidbakhshfard et al, 2020 ; Baltazar et al, 2021 ; Rasul et al, 2021 ). These phytotonic effects of SWE arise from the complex composition of metabolites, which are rich in macro- and micronutrients, carbohydrates, amino acids, and plant hormones, such as auxins and cytokinin ( De Abreu et al, 2008 ; Tan et al, 2021 ).…”