Phaeophyceaean (Brown Algal) Extracts Activate Plant Defense Systems in Arabidopsis thaliana Challenged With Phytophthora cinnamomi

Abstract

Seaweed extracts are important sources of plant biostimulants that boost agricultural productivity to meet current world demand. The ability of seaweed extracts based on either of the Phaeophyceaean species Ascophyllum nodosum or Durvillaea potatorum to enhance plant growth or suppress plant disease have recently been shown. However, very limited information is available on the mechanisms of suppression of plant disease by such extracts. In addition, there is no information on the ability of a combination of extracts from A. nodosum and D. potatorum to suppress a plant pathogen or to induce plant defense. The present study has explored the transcriptome, using RNAseq, of Arabidopsis thaliana following treatment with extracts from the two species, or a mixture of both, prior to inoculation with the root pathogen Phytophthora cinnamomi. Following inoculation, five time points (0−24 h post-inoculation) that represented early stages in the interaction of the pathogen with its host were assessed for each treatment and compared with their respective water controls. Wide scale transcriptome reprogramming occurred predominantly related to phytohormone biosynthesis and signaling, changes in metabolic processes and cell wall biosynthesis, there was a broad induction of proteolysis pathways, a respiratory burst and numerous defense-related responses were induced. The induction by each seaweed extract of defense-related genes coincident with the time of inoculation showed that the plants were primed for defense prior to infection. Each seaweed extract acted differently in inducing plant defense-related genes. However, major systemic acquired resistance (SAR)-related genes as well as salicylic acid-regulated marker genes (PR1, PR5, and NPR1) and auxin associated genes were found to be commonly up-regulated compared with the controls following treatment with each seaweed extract. Moreover, each seaweed extract suppressed P. cinnamomi growth within the roots of inoculated A. thaliana by the early induction of defense pathways and likely through ROS-based signaling pathways

The effect of seaweed extract on tomato plant growth, productivity and soil

“…Santaniello et al (2017) used another SWE to report the effects on photosynthetic performance in Arabidopsis. Islam et al (2020) reported SWE increased root growth in Arabidopsis. Given the effects of SWE reported across many different farming and growth environments using different crops, this implies their mode of action is conserved with an inherent plasticity when used as a foliar spray or soil application.…”

“…Studies using Arabidopsis, soybean and tomato plants have demonstrated that the application of SWE can improve plant tolerance to abiotic stresses such as drought, freezing and salt (Nair et al 2012;Martynenko et al 2016;Santaniello et al 2017;Goni et al 2018;Jithesh et al 2019). At a molecular level, laboratory studies have demonstrated that certain SWE have an intriguing capacity to activate plant defence response systems including the Systemic Acquired Resistance mechanism (Goni et al 2016;Islam et al 2020;Omidbakhshfard et al 2020). In addition, soil-applied SWE provide a wide range of nutrients for soil microbiota utilisation.…”

“…We hypothesise that the soil application of a SWE made from two brown seaweeds (Ascophyllum nodosum and Durvillaea potatorum) would enhance plant growth and soil biology and would influence the plant-soil ecosystem. We chose an extract made from two seaweeds because transcriptomics research has shown an expanded set of plant gene responses compared with the extracts made from single-origin seaweeds (Islam et al 2020). For new insights, we investigated tomato plant growth and soil biology parameters concurrently.…”

Seaweed-Based Compounds and Products for Sustainable Protection against Plant Pathogens

“…The treatment of the broccoli with the seaweed extract reduced the number of the plasmodia formed in the roots [ 144 ]. Islam et al [ 134 ] studied the protective effects of Seasol ® , ANE and an alkaline extract of Duvillaea potatorum on A. thaliana , before and after inoculation with the root pathogen Phytophthora cinnamomi, using a transcriptomics approach. Global transcriptomics analysis revealed that Seasol Commercial ® reduced the progression of P. cinnamomi by regulating proteolytic pathways, respiratory burst, and various defense-related responses.…”

“…Global transcriptomics analysis revealed that Seasol Commercial ® reduced the progression of P. cinnamomi by regulating proteolytic pathways, respiratory burst, and various defense-related responses. Overall, each seaweed extract acted differently, but all were successful in inducing plant defense-related genes [ 134 ]. The root drench treatment of 0.5% Dalgin ® (Sustainable Agro Solutions, Lleida, Spain), is another commercial extract prepared from A. nodosum that can significantly reduce the severity of a P. capsici infection of tomatoes by inducing the expression of several defense-related genes and also the activity of many oxidative enzymes [ 142 ].…”