Plant Responses Underlying Timely Specialized Metabolites Induction of Brassica Crops

Abstract

A large subset of plant stress-signaling pathways, including those related with chemical defense production, exhibit diurnal or circadian oscillations. However the extent to which diurnal or circadian time influences the stress mediated accumulation of plant specialized metabolites remains largely unknown. Because plant responses to physical stress (e.g., wounding) is considered a common component of mounting a response against a broad range of environmental stresses, including herbivory, we have utilized mechanical wounding as the stress stimulus to determine the direct contribution of time of day on the induced defenses of Brassica crops. We analyzed glucosinolates (GSLs) from leaves of broccoli (Brassica oleracea) and turnip greens (Brassica rapa) following exposure to mechanical wounding at dawn (ZT0), mid-day (ZT4), and dusk (ZT8). Several GSLs differentially accumulated and their changes depended upon the time of day at wounding was performed. This response varied considerably between species. In a parallel experiment, we investigated whether diurnal activation of Brassica phytochemicals in response to wounding might prime plants against herbivore attack. Results showed that maximal response of plant chemical defense against larvae of the generalist pest Mamestra brassicae occurred at ZT0 in broccoli and ZT8 in turnip greens. Metabolome analysis for global trends of time dependent compounds showed that sulfur-containing phytochemicals, GSL hydrolysis products, auxin-signaling components, and other metabolites activators of plant disease resistance (nicotinamide and pipecolate) had important contributions to the responses of M. brassicae feeding behavior in broccoli at morning. Overall, the findings in this study highlight a significant role for time of day in the wound stress responsive metabolome, which can in turn affect plant-herbivore interactions.

Time of day of leaf wounding determines plant biomass and affects the interplay between growth and defence in Brassica crops

“…As expected, the most induced compounds after wounding were indole GSLs, but with high variation in timing of injury among genotypes. Previous studies have also shown that induction of specialized metabolites after wounding or herbivory varies across species and genotypes in terms of their circadian or diurnal response (Arimura et al 2008;Kim et al 2011;Baldwin & Meldau 2013;Doghri et al 2022). Notably, several aliphatic GSL and phenolic compounds were lower after morning and evening wounding than in controls, while midday treatment induced several such compounds (Fig.…”

“…Consistent with such oscillations, specialized metabolites that mediate plant defence are synchronized with Lepidoptera, aphid and pathogen circadian behaviour in Arabidopsis thaliana and related Brassica crops (Goodspeed et al 2012(Goodspeed et al , 2013Lei et al 2019;Rupp et al 2020). More recently, Doghri et al (2022) revealed that induction of glucosinolates (GSL), major plant defence metabolites in the Brassicaceae, depends on the time during the day at which the stress event (attack) takes place. However, the internal reshaping of plant growth under daily stress sensing, the circadian and photoperiodic gating of plant responses, and their metabolic coordination remain to be investigated.…”

A changing world: the role of phenotypic plasticity in host-parasitoid interactions facing extreme temperatures

“…Temperature records from the Veenkampen 3 , Wageningen, The Netherlands, weather station indicate daily maximal and minimal temperatures fluctuating between 11-33 ℃ and 0.1-20.5℃, respectively, with an average daily temperature variation (i.e., maximal -minimal temperature) of 11.6 ℃. Although the effects of thermal variation were not analysed in this dataset, effects of temperature and herbivore species diversity on plant phytochemical profiles have been reported in other studies, suggesting that both factors are likely to interact to mediate community dynamics (Doghri et al, 2021;Kask et al, 2016;Mikkelsen et al, 2015;Truong et al, 2014). Ecosystems dynamics are marked by seasonality and the composition of the previous species assemblage influences the composition of the subsequent assemblage (Heinen et al, 2022;Stam et al, 2019).…”

“…Plant phytochemistry fluctuates over time (e.g. year, season, day), allowing plants to optimise their metabolic activity to match their environmental conditions (Doghri et al, 2021;Gols et al, 2007). Mechanical wounding of Lima bean (Phaseolus lunatus L.; Fabaceae) leaves as a mimic of herbivore damage during the photo-or scotophase resulted in differential emission of herbivore induced plant volatiles (HIPVs) (Arimura et al, 2008).…”

“…Similarly, plant metabolite composition varies across time, differentially affecting the fitness of hosts and parasitoids (Liebelt et al, 2019). The composition of secondary metabolites in Brassicaceae crops in response to herbivory by Mamestra brassicae L. (Lepidoptera: Noctuidae) peaked at dawn or dusk compared to mid-day, suggesting that plants may anticipate potential threats to match their defences with the timing of a likely attack (Doghri et al, 2021). Recent studies indicate that plants having coevolved with multiple herbivore species may use circadian and seasonal rhythms to anticipate and adapt their defence strategies (Mertens et al, 2021b;Philbin et al, 2021).…”