Plant Flavonoids in Mediterranean Species: A Focus on Flavonols as Protective Metabolites under Climate Stress

Flavonoids are specialized metabolites largely widespread in plants where they play numerous roles including defense and signaling under stress conditions. These compounds encompass several chemical subgroups such as flavonols which are one the most represented classes. The most studied flavonols are kaempferol, quercetin and myricetin to which research attributes antioxidative properties and a potential role in UV-defense through UV-screening mechanisms making them critical for plant adaptation to climate change. Despite the great interest in flavonol functions in the last decades, some functional aspects remain under debate. This review summarizes the importance of flavonoids in plant defense against climate stressors and as signal molecules with a focus on flavonols in Mediterranean plant species. The review emphasizes the relationship between flavonol location (at the organ, tissue and cellular scales) and their function as defense metabolites against climate-related stresses. It also provides evidence that biosynthesis of flavonols, or flavonoids as a whole, could be a crucial process allowing plants to adapt to climate change, especially in the Mediterranean area which is considered as one of the most sensitive regions to climate change over the globe.

CRISPR/Cas9 knockout of EPFL10 reduces stomatal density while maintaining photosynthesis and enhancing water conservation in rice

Rice production is of paramount importance for global nutrition and potential yields will be detrimentally affected by climate change. Rice stomatal developmental genetics were explored as a mechanism to improve water use efficiency while maintaining yield under climate stress. Gene-editing of STOMAGEN and its paralog, EPFL10, using CRISPR/Cas9 in rice cv. Nipponbare yielded lines with altered stomatal densities that were functionally characterized. CRISPR/Cas9 mediated knockouts of EPFL10 and STOMAGEN yielded lines with c. 80% and 25% of wild-type stomata, respectively. epfl10 lines with small reductions in stomatal densities are able to conserve water to similar extents as stomagen lines with large stomatal density reductions but do not suffer from any concomitant reductions in stomatal conductance, carbon assimilation, or thermoregulation. The duplicate of STOMAGEN, EPFL10, is a weak positive regulator of stomatal development in rice. epfl10 lines maintained wild-type physiological characteristics while conserving more water. Modest reductions in stomatal densities may be a climate-adaptive approach in rice that can safeguard yield.

Integrated framework for rapid climate stress testing on a monthly timestep

“Bottom-up” methods are increasingly used to assess the vulnerability of water systems to climate change. Central to these methods is the climate “stress test”, where the system is subjected to various climatic changes to test for unacceptable outcomes. We present a framework for climate stress testing on a monthly timestep, suitable for systems whose dominant dynamic is seasonal or longer (eg. water resource systems with carry-over storage). The framework integrates multi-site stochastic climate generation with perturbation methods and in-built rainfall runoff modelling. The stochastic generation includes a low frequency component suitable for representing multi-annual fluctuations. Multiple perturbation options are provided, ranging from simple delta change through to altered seasonality and low frequency dynamics. The framework runs rapidly, supporting comprehensive multi-dimensional stress testing without recourse to supercomputing facilities. We demonstrate the framework on a large water resource system in southern Australia. The Matlab/Octave framework is freely available for download from https://doi.org/10.5281/zenodo.5617008.

Remote sensing reveals multi-decadal losses of tree cover in California driven by increasing fire disturbance and climate stress

Forests provide natural climate solutions for sequestering carbon and mitigating climate change yet are threatened by increasing temperatures and disturbance. Accurate information on vegetation dynamics is lacking in some regions with forest carbon offset programs and dense forests like California. To address this, we combined remote sensing observations with geospatial databases to develop annual maps of vegetation cover (tree, shrub, herbaceous) and disturbance type (fires, harvest, and forest die-off) in California at 30 m resolution from 1985 to 2021. California lost 3783 km2 of its tree cover area (5.5% relative to initial cover). Early gains in tree cover area were more than offset by fire-driven declines, resulting in greater shrub and herbaceous cover area. Fires and tree cover area loss occurred where temperatures were high or increasing, whereas tree cover gain occurred in cooler areas. Disturbance and warming are threatening the integrity of California's forests and its carbon offsets program.

Constraints to using livestock to meet dietary needs in developing countries: role of vaccines.

Animal agriculture and animal-source foods (ASF) play a critical role in food security, childhood nutrient sufficiency, and economic development in sub-Saharan Africa. Here, we consider constraints to production of ASF in Africa with a focus on infectious animal diseases and climate stress and their control, by vaccines and selective breeding, respectively. This is not a meta-analysis but rather is meant to act as an overview or primer for discussing the value of livestock in developing countries, constraints to this, possible solutions, and finally some roadblocks to accomplishing this. The material provided is based on our own knowledge gained through careers in this field as well as discussions with colleagues.

The past, present, and future of multiple wheat and maize breadbasket shocks

Simultaneous yield shocks in multiple breadbaskets pose a potential threat to global food security, yet the historical risks and causes of such shocks are poorly understood. Here, we compile a dataset of subnational maize and wheat yield anomalies in 25 countries dating back to 1900 to better characterize the past, present, and future risk of multiple breadbasket shocks. We find that years in which at least half of all maize or wheat breadbaskets fall 10% (5%) below expected yields has occurred in ~2-3% (~14-16%) of years over the last century. Importantly, multiple breadbasket shocks have been decreasing in frequency from 1930 to 2017. The El Niño Southern Oscillation (ENSO) most strongly affects the probability of multiple maize breadbasket shocks, while the North Atlantic Oscillation (NAO) most strongly affects the probability of multiple wheat breadbasket shocks, each influencing the probability by up to 40%. The effect of climate change on climate stress in maize and wheat breadbaskets is mixed; extreme heat will increase uniformly, agricultural soil moisture stress will remain constant or increase, but hydrological stress (as measured by runoff) will remain constant or decrease in breadbasket regions.

Assessing the Contribution of Climate-smart Agriculture Practices on the Resilience of Maize Farmers in Bungoma County, Kenya

Climate variability threatens farmers’ livelihoods. Efforts to address climate stress recognise climate-smart agriculture (CSA) as a promising approach to minimising the damage caused by increasing weather variability. However, the effect of CSA practices on the resilience of maize farmers in the face of climate variability is not well understood. This study assesses the effects of CSA practices on the resilience of maize farmers. Using primary data from 250 randomly sampled maize farmers in Kenya, a resilience index was generated and then analysed using a structural equation model. The results show that CSA practices increase the resilience of farmers, suggesting enhanced resilience to climate variability. CSA practices improve farmers’ food security and welfare, and their adoption should be promoted.

Phyllosphere Community Assembly and Response to Drought Stresson Common Tropical and Temperate Forage Grasses

Grasslands represent a critical ecosystem important for global food production, soil carbon storage, and water regulation. Current intensification and expansion practices add to the degradation of grasslands and dramatically increase greenhouse gas emissions and pollution. Thus, new ways to sustain and improve their productivity are needed. Research efforts focus on the plant-leaf microbiome, or phyllosphere, because its microbial members impact ecosystem function by influencing pathogen resistance, plant hormone production, and nutrient availability through processes including nitrogen fixation. However, little is known about grassland phyllospheres and their response to environmental stress. In this study, globally dominant temperate and tropical forage grass species were grown in a greenhouse under current climate conditions and drought conditions that mimic future climate predictions to understand if (i) plant host taxa influence microbial community assembly, (ii) microbial communities respond to drought stress, and (iii) phyllosphere community changes correlate to changes in plant host traits and stress-response strategies. Community analysis using high resolution sequencing revealed Gammaproteobacteria as the dominant bacterial class, which increased under severe drought stress on both temperate and tropical grasses while overall bacterial community diversity declined. Bacterial community diversity, structure, and response to drought were significantly different between grass species. This community dependence on plant host species correlated with differences in grass species traits, which became more defined under drought stress conditions, suggesting symbiotic evolutionary relationships between plant hosts and their associated microbial community. Further understanding these strategies and the functions microbes provide to plants will help us utilize microbes to promote agricultural and ecosystem productivity in the future. IMPORTANCE Globally important grassland ecosystems are at risk of degradation due to poor management practices compounded by predicted increases in severity and duration of drought over the next century. Finding new ways to support grassland productivity is critical to maintaining their ecological and agricultural benefits. Discerning how grassland microbial communities change in response to climate stress will help us understand how plant-microbe relationships may be useful to sustainably support grasslands in the future. In this study, phyllosphere community diversity and composition was significantly altered under drought conditions. The significance of our research is demonstrating how severe climate stress reduces bacterial community diversity, which previously was directly associated with decreased plant productivity. These findings guide future questions about functional plant-microbe interactions under stress conditions, greatly enhancing our understanding of how bacteria can increase food security by promoting grassland growth and resilience.