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Drought stress severely affects crop productivity and threatens food security. As current trends of global warming are predicted to exacerbate droughts, developing drought-resilient crops becomes urgent. Here, we used the drought-tolerant (BW35695) and drought-sensitive (BW4074) wheat varieties to investigate the physiological, biochemical, and leaf proteome responses underpinning drought tolerance. In response to drought, the tolerant variety had higher osmolyte accumulation and maintained higher leaf water content than the sensitive variety. BW35695 also had an enhanced antioxidant enzyme capacity and reduced reactive oxygen species (ROS), resulting in diminished membrane lipid damage, as reflected by malondialdehyde content. Proteomic analysis revealed that drought-induced differential expression of proteins involved in diverse biological processes in both wheat varieties, including primary and secondary metabolism, protein synthesis/folding/degradation, defense/ROS detoxification, energy, transcription, and cell structure. Notably, photosynthesis emerged as the most enriched biochemical process targeted for suppression in the drought-tolerant BW35695 wheat, but not in drought-sensitive BW4074, possibly as a survival strategy for averting cell damage inflicted by photosynthesis-derived ROS. Additionally, protein synthesis-related proteins were highly upregulated in BW35695, presumably to drive cell-wide stress-adaptive responses. The protein network identified here will be useful in further studies to understand the molecular basis for divergent drought response phenotypes in crops.

Plants reprogramme their proteome to alter cellular metabolism for effective stress adaptation. Intracellular proteomic responses have been extensively studied, and the extracellular matrix stands as a key hub where peptide signals are generated/processed to trigger critical adaptive signal transduction cascades inaugurated at the cell surface. Therefore, it is important to study the plant extracellular proteome to understand its role in plant development and stress response. This study examined changes in the soluble extracellular sub-proteome of sorghum cell cultures exposed to a combination of sorbitol-induced osmotic stress and heat at 40 °C. The combined stress significantly reduced metabolic activity and altered protein secretion. While cells treated with osmotic stress alone had elevated proline content, the osmoprotectant in the combined treatment remained unchanged, confirming that sorghum cells exposed to combined stress utilise adaptive processes distinct from those invoked by the single stresses applied separately. Reactive oxygen species (ROS)-metabolising proteins and proteases dominated differentially expressed proteins identified in cells subjected to combined stress. ROS-generating peroxidases were suppressed, while ROS-degrading proteins were upregulated for protection from oxidative damage. Overall, our study provides protein candidates that could be used to develop crops better suited for an increasingly hot and dry climate.

Drought stress adversely affects plant growth, often leading to total crop failure. Upon sensing soil water deficits, plants switch on biosynthesis of abscisic acid (ABA), a stress hormone for drought adaptation. Here, we used exogenous ABA application to dark-grown sorghum cell suspension cultures as an experimental system to understand how a drought-tolerant crop responds to ABA. We evaluated intracellular and secreted proteins using isobaric tags for relative and absolute quantification. While the abundance of only ~ 7% (46 proteins) intracellular proteins changed in response to ABA, ~32% (82 proteins) of secreted proteins identified in this study were ABA responsive. This shows that the extracellular matrix is disproportionately targeted and suggests it plays a vital role in sorghum adaptation to drought. Extracellular proteins responsive to ABA were predominantly defense/detoxification and cell wall-modifying enzymes. We confirmed that sorghum plants exposed to drought stress activate genes encoding the same proteins identified in the in vitro cell culture system with ABA. Our results suggest that ABA activates defense and cell wall remodeling systems during stress response. This could underpin the success of sorghum adaptation to drought stress.

Abstract Introduction Soil degradation coupled with poor access to organic nutrient resources remains a major constraint in increased crop productivity in sub‐Saharan Africa, thus hindering the continent's efforts in achieving the United Nations' Sustainable Development Goals, particularly goals 1 (end poverty), 2 (zero hunger) and 3 (improve human health). Water treatment residual (WTR), a by‐product of clean water treatment, has been identified as an alternative organic nutrient resource for crop production. However, there are some inconsistences in soil phosphorus (P) dynamics following aluminium WTR (Al‐WTR) application. Materials & Methods A laboratory experiment was conducted to evaluate the P sorption of a sandy soil amended with 10% Al‐WTR, 10% compost (C) as a quasi‐control, 10% C + 10% Al‐WTR (10% coamendment) and 5% C + 5% Al‐WTR (5% coamendment) under varying levels of pH, particle size and P concentration. We calculated crop P fertilizer requirements under different amendments. Results The results demonstrated that all amendments exceeded the minimum of 0.2 mg P L−1 needed in soil solution at equilibrium to maintain plant growth. However, the maximum P sorption capacity was higher for 10% Al‐WTR single amendment, ranging from 770 to 1000 mg P Kg−1, and from 714 to 1000 mg P Kg−1 and 555 to 909 mg P Kg−1 for 10% and 5% coamendments, respectively, across a range of pH and soil particle size fractions. The coamendments showed a reduction in crop P fertilizer requirements by ranges of 30–60% and 60–70% for the 10% and 5% coamendment levels, respectively, across different pH and particle sizes, relative to 10% Al‐WTR. Conclusion Results show that the use of 5% coamendment in sandy soils increases P availability sufficiently to improve crop yields. The results provide scope for using Al‐WTR coamendments to rebuild soil health in sandy soils in urban agriculture and increase macronutrient provision in crops to support human health.

Crop growth and yield are affected by salinity, which causes oxidative damage to plant cells. Plants respond to salinity by maintaining cellular osmotic balance, regulating ion transport, and enhancing the expression of stress-responsive genes, thereby inducing tolerance. As a byproduct of heme oxygenase (HO)-mediated degradation of heme, carbon monoxide (CO) regulates plant responses to salinity. This study investigated a CO-mediated salt stress tolerance mechanism in sorghum seedlings during germination. Sorghum seeds were germinated in the presence of 250 mM NaCl only, or in combination with a CO donor (1 and 1.5 μM hematin), HO inhibitor (5 and 10 μM zinc protoporphyrin IX; ZnPPIX), and hemoglobin (0.1 g/L Hb). Salt stress decreased the germination index (47.73%) and root length (74.31%), while hydrogen peroxide (H2O2) (193.5%), and proline (475%) contents increased. This increase correlated with induced HO (137.68%) activity and transcripts of ion-exchanger and antioxidant genes. Salt stress modified vascular bundle structure, increased metaxylem pit size (42.2%) and the Na+/K+ ratio (2.06) and altered primary and secondary metabolites. However, exogenous CO (1 μM hematin) increased the germination index (63.01%) and root length (150.59%), while H2O2 (21.94%) content decreased under salt stress. Carbon monoxide further increased proline (147.62%), restored the vascular bundle structure, decreased the metaxylem pit size (31.2%) and Na+/K+ ratio (1.46), and attenuated changes observed on primary and secondary metabolites under salt stress. Carbon monoxide increased HO activity (30.49%), protein content, and antioxidant gene transcripts. The alleviatory role of CO was abolished by Hb, whereas HO activity was slightly inhibited by ZnPPIX under salt stress. These results suggest that CO elicited salt stress tolerance by reducing oxidative damage through osmotic adjustment and by regulating the expression of HO1 and the ion exchanger and antioxidant transcripts.

Soil health underpins ecosystem services like food security and therefore underpins human health. Poor soil health is a global problem which is hindering attempts to deliver the UN’s Sustainable Development Goals. We focus on goals 3 (human health), 13 (climate change) which are intimately linked to goal 15 (soil health). Soil health is arguably most fragile in regions such as sub-Saharan Africa (SSA) where aged soils are characterised by poor nutrient and water holding capacity, and are largely deficient in micronutrients such as Zinc. Poor soil health coupled with the largely cereal-based diets can mean that micronutrient malnutrition is high in the region. In sub-Saharan Africa, where much of the population is too poor to purchase mineral supplements, poor soil health (SDG15) can therefore negatively impact on human health (SDG3). We surveyed 3661 school children aged 13–15 in three African countries, Ghana, South Africa and Zimbabwe, for their ‘Attitudes, Behaviours and Competencies’ of soil, which we termed ‘ABC’. The ‘ABC’ survey results showed significant soil illiteracy. The survey showed that although students were generally equipped with a good attitude to (overall 52% positive) and behaviour towards soil (overall 60% engagement), they had little competency as to how to improve soil health (overall 23% knowledge). For example, less than 35% of respondents across all countries know that soil is living. Less than 13% of students are aware of the important role of soil in climate change mitigation. We believe that these two knowledge gaps must be addressed for Generation Z to understand the important linkages between climate change, soil and human health. We propose a hands-on ‘ethics of care’ approach to engage society with soil, piggybacking on existing climate change educational resources by building terrariums with living soil can empower children to learn about soil, plant, human and planetary health. The future of food security depends on Generation Z having soil literacy. Our survey clearly shows that students who think farming is a good way to make money have significantly higher levels of overall soil literacy. We propose that the future of human health depends on soil literacy.

Nations can build and rebuild degraded soils to help address climate change and potentially improve the nutritional content of food if we change policies that allow the addition of safe mineral and organic wastes to soil. We present a framework that facilitates the transition from intensive conventional to more regenerative farming practices by considering soil's natural cycle. Our paper is presented in three parts. Firstly, we consider that 'soil is living'; just like humans, the soil biome needs a balanced diet of macro and micronutrients as well as a nurturing environment. We simplify the soil science and take a systems approach which focuses on restoring soil's natural cycle to benefit both health (by increasing micronutrients in soil) and wealth (through climate change adaptation and mitigation). Secondly, we consider the scale of the problem of soil degradation and the timescales involved in rebuilding soils and barriers to implementation. Thirdly, we propose a potential framework which enables communities to identify what might be missing from soil's natural cycle. This framework helps communities consider how they might change soil texture by addition and manipulation of both minerals and organic matter. We present an educational tool, ‘soil in a jar’ based on a narrative of nurturing soil which is designed to engage and inspire society to get their hands dirty. Communities can use the framework to produce locally specific solutions to restore their soil's natural cycle and rebuild their local and national economies.