Abiotic Stress Resilience Research Articles

Metabolic nitrogen and carbohydrate pools as potential quality indicators of supply chains for ornamental young plants

The plasticity and physiological functions of metabolic nitrogen (N) and carbohydrate pools in the tissues of axillary shoot tip cuttings are poorly understood despite their pivotal role in pre-harvest growth, post-harvest abiotic stress resilience, survival and adventitious root (AR) formation in young plant supply chains for ornamental crops. Therefore, we studied the N and carbohydrate pools in response to contrasting experimental environments by both the graduated N supply of stock plants and the different dark storage amounts of the cuttings as well as during multi-seasonal transport of commercial cuttings from low-latitude stock plant facilities.The initial survey of cuttings from the supply chains confirmed species-specific optimal total nitrogen (Nt) levels and indicated further species differences both in Nt allocation to metabolic N pools and in the total carbon (Ct)/Nt ratio in Chrysanthemum (CHRY), Euphorbia (POI), Impatiens (IMP), Osteospermum (OSTEO) and Pelargonium (PEL). For CHRY and PEL, frequency distributions of the Nt content revealed that a significant percentage of commercial cuttings is not optimally supplied. The PEL cuttings responded to experimental dark storage with a gradual increase in mobile organic N pools at the expense of the proportion of Nt of the matrix protein pool, which corresponded to reduced survival and rooting capacity, whereas the Nt and nitrate levels remained unchanged. Analyses of commercial cuttings confirmed regular incidents of shifts in Nt allocation from insoluble protein-N to mobile N pools; these shifts coincided with severe carbohydrate depletions during transport. Therefore, compared with leaf tissues, stem tissues displayed a higher resilience against carbohydrate depletion.In conclusion, monitoring deviation ranges and changes among N pools in addition to carbohydrates and Nt is suggested. This monitoring is appropriate not only during growth before harvest but also throughout postharvest and helps to identify risks of low survival rate and low rooting before cuttings are planted. As a first parameter, a set of indicators for decision support is suggested. In this regard, the potential of near-infrared spectroscopy (NIRS) is discussed as rapid diagnostic tool that can easily be applied at critical points of the supply chains.

Omics Approaches for Engineering Wheat Production under Abiotic Stresses.

Abiotic stresses greatly influenced wheat productivity executed by environmental factors such as drought, salt, water submergence and heavy metals. The effective management at the molecular level is mandatory for a thorough understanding of plant response to abiotic stress. Understanding the molecular mechanism of stress tolerance is complex and requires information at the omic level. In the areas of genomics, transcriptomics and proteomics enormous progress has been made in the omics field. The rising field of ionomics is also being utilized for examining abiotic stress resilience in wheat. Omic approaches produce a huge amount of data and sufficient developments in computational tools have been accomplished for efficient analysis. However, the integration of omic-scale information to address complex genetics and physiological questions is still a challenge. Though, the incorporation of omic-scale data to address complex genetic qualities and physiological inquiries is as yet a challenge. In this review, we have reported advances in omic tools in the perspective of conventional and present day approaches being utilized to dismember abiotic stress tolerance in wheat. Attention was given to methodologies, for example, quantitative trait loci (QTL), genome-wide association studies (GWAS) and genomic selection (GS). Comparative genomics and candidate genes methodologies are additionally talked about considering the identification of potential genomic loci, genes and biochemical pathways engaged with stress resilience in wheat. This review additionally gives an extensive list of accessible online omic assets for wheat and its effective use. We have additionally addressed the significance of genomics in the integrated approach and perceived high-throughput multi-dimensional phenotyping as a significant restricting component for the enhancement of abiotic stress resistance in wheat.

Functional Diversity of Diterpene Synthases in the Biofuel Crop Switchgrass.

Diterpenoids constitute a diverse class of metabolites with critical functions in plant development, defense, and ecological adaptation. Major monocot crops, such as maize (Zea mays) and rice (Oryza sativa), deploy diverse blends of specialized diterpenoids as core components of biotic and abiotic stress resilience. Here, we describe the genome-wide identification and functional characterization of stress-related diterpene synthases (diTPSs) in the dedicated bioenergy crop switchgrass (Panicum virgatum). Mining of the allotetraploid switchgrass genome identified an expansive diTPS family of 31 members, and biochemical analysis of 11 diTPSs revealed a modular metabolic network producing a diverse array of diterpenoid metabolites. In addition to ent-copalyl diphosphate (CPP) and ent-kaurene synthases predictably involved in gibberellin biosynthesis, we identified syn-CPP and ent-labda-13-en-8-ol diphosphate (LPP) synthases as well as two diTPSs forming (+)-labda-8,13E-dienyl diphosphate (8,13-CPP) and ent-neo-cis-trans-clerodienyl diphosphate (CT-CLPP) scaffolds not observed previously in plants. Structure-guided mutagenesis of the (+)-8,13-CPP and ent-neo-CT-CLPP synthases revealed residue substitutions in the active sites that altered product outcome, representing potential neofunctionalization events that occurred during diversification of the switchgrass diTPS family. The conversion of ent-CPP, ent-LPP, syn-CPP, and ent-neo-CT-CLPP by promiscuous diTPSs further yielded distinct labdane-type diterpene olefins and alcohols. Of these metabolites, the formation of 9β-hydroxy-syn-pimar-15-ene and the expression of the corresponding genes were induced in roots and leaves in response to oxidative stress and ultraviolet irradiation, indicating their possible roles in abiotic stress adaptation. Together, these findings expand the known chemical space of diterpenoid metabolism in monocot crops toward systematically investigating and ultimately improving stress resilience traits in crop species.

Strigolactones: multi-level regulation of biosynthesis and diverse responses in plant abiotic stresses

Strigolactones (SLs) are a small class of diverse metabolites derived from the carotenoid pathway. These active biomolecules are a recent inclusion to the list of non-traditional phytohormones or plant growth regulators. Previous reports and articles have discussed their pro-regulatory roles in plant growth, development, signaling and delay of senescence. However, the multi-level control of SL biosynthesis is less known. The anabolic genes are strictly regulated through synchronized co-operation between crucial phytohormones. Epigenetic and microRNA-mediated post-transcriptional regulation fine tunes the cellular accumulation of these putative phytohormones. The question now arises that why such multi-level intricate regulation at all is required for SLs, which were originally detected as under-rated germination and rhizosphere stimulants. This review answers the question in the backdrop of the positive roles of SLs in promoting abiotic stress resilience across diverse plant species. SLs reportedly accumulate in the plant tissues in response to environmental sub-optimal conditions like drought, salinity, temperature, nutrient deprivation and oxidative stresses. Fluctuations in the light quality and intensity also trigger variable accumulation of SLs, indicating their potential in regulating light stress as well. Though the exact roles of SLs have not yet been characterized, it is predicted that they possibly induce the expression of downstream osmolytes to maintain metabolic homeostasis in the stressed cells. Thus, exogenous treatments or transgenic approaches for higher SL bioaccumulation can be potential strategies for developing multiple abiotic stress tolerance in crops and plants.

Improved Salinity Resilience in Black Bean by Seed Elicitation Using Organic Compounds

Core Ideas Black bean cultivars were extremely susceptible to high salinity stress. Seed elicitation improved salinity stress resilience. Chitosan oligosaccharide and marine peptide were used for seed elicitation. Adaptive response to salinity stress varied among black bean cultivars. Seed elicitation induced phenolic‐linked antioxidant enzyme responses. The adaptive responses of plants to abiotic stress include stimulation of secondary metabolites and endogenous antioxidant enzymes through up‐regulation of the pentose phosphate pathway (PPP). Therefore improving abiotic stress resilience in food crops through upregulation of critical redox‐linked anabolic PPP and enhancement of phenolic‐linked antioxidant enzyme responses has merit. This study evaluated the effects of seed elicitor treatments (chitosan oligosaccharide [COS] Kong Poong Bio, Jeju, Korea, and marine hydrolysate [GroPro], Icelandic Bioenhancer, Harrison, NY) to improve salinity stress resilience through up‐regulation of PPP in black bean (Phaseolus vulgaris L.) cultivars. Eclipse and Zenith cultivars were subjected to elicitor treatments (1%) and then 1 wk after germination were transplanted into three soil salinity treatments (no salt, 2–3, and 5–6 dS m−1) in greenhouse. Elicitation resulted in enhanced survival at medium salt stress (2–3 dS m−1), however none survived more than 55 to 60 d post germination under high salt stress (5–6 dS m−1). Stimulation of phenolic biosynthesis through up‐regulation of PPP was confirmed in Eclipse, while Zenith exhibited higher reliance by stimulation of endogenous antioxidant enzyme responses to counter salinity stress. GroPro induced elicitation improved total soluble phenolic content (60 d) and higher glucose‐6‐phosphate dehydrogenase (G6PDH) activity (45 d) in Eclipse. In Zenith, GroPro stimulated antioxidant enzyme responses (superoxide dismutase [SOD] and guaiacol peroxidase [GPX]) during later growth stages, while COS elicitation improved antioxidant response in early stages. Therefore seed elicitation can be a selective strategy to improve salinity stress resilience in black bean.

Strigolactones Biosynthesis and Their Role in Abiotic Stress Resilience in Plants: A Critical Review.

Strigolactones (SLs), being a new class of plant hormones, play regulatory roles against abiotic stresses in plants. There are multiple hormonal response pathways, which are adapted by the plants to overcome these stressful environmental constraints to reduce the negative impact on overall crop plant productivity. Genetic modulation of the SLs could also be applied as a potential approach in this regard. However, endogenous plant hormones play central roles in adaptation to changing environmental conditions, by mediating growth, development, nutrient allocation, and source/sink transitions. In addition, the hormonal interactions can fine-tune the plant response and determine plant architecture in response to environmental stimuli such as nutrient deprivation and canopy shade. Considerable advancements and new insights into SLs biosynthesis, signaling and transport has been unleashed since the initial discovery. In this review we present basic overview of SL biosynthesis and perception with a detailed discussion on our present understanding of SLs and their critical role to tolerate environmental constraints. The SLs and abscisic acid interplay during the abiotic stresses is particularly highlighted.Main Conclusion: More than shoot branching Strigolactones have uttermost capacity to harmonize stress resilience.

The effects of climate change associated abiotic stresses on maize phytochemical defenses

Reliable large-scale maize production is an essential component of global food security; however, sustained efforts are needed to ensure optimized resilience under diverse crop stress conditions. Climate changes are expected to increase the frequency and intensity of both abiotic and biotic stress. Protective phytochemicals play an important role in both abiotic stress resilience and resistance to biotic challenges, yet the concentration and composition of these phytochemicals are also dependent on climate variables. We review the research on the effects of climate change associated abiotic stresses on three classes of maize defense metabolites, including benzoxazinoids, volatile organic compounds, and terpenoid phytoalexins. Despite significant knowledge gaps that still exist, it is evident that climate change will influence maize phytochemicals associated with resilient productivity. While broad generalizations are not yet possible, climate induced changes in phytochemicals are context specific and dependent upon developmental stage and tissue type. Under conditions of drought, maize modulates different classes of defense phytochemicals to protect the above-and belowground tissues. Aboveground the benzoxazinoid defenses are stimulated, but belowground terpenoid phytoalexins are predominantly deployed. Changes in the allocation or distribution of the different classes of defense metabolites or signaling molecules have the potential to further shape the biodiversity and abundance of pests within the maize agroecosystem. A better understanding of the underlying genetics, biosynthetic pathways, regulation and precise biological roles of maize phytochemicals modulated by arrays of climatic conditions will be required to ensure optimal plant resilience and productivity in the face of combined biotic and abiotic stresses.

Ancestral QTL alleles from wild emmer wheat improve grain yield, biomass and photosynthesis across enviroinments in modern wheat

Wild emmer wheat (Triticum turgidum ssp. dicoccoides) is considered a promising source for improving drought resistance in domesticated wheat. Nevertheless, wild germplasm has not been widely used in wheat breeding for abiotic stress resilience. In the current study, a near isogenic line NIL-7A-B-2, introgressed with a drought-related QTL from wild emmer wheat on chromosome 7A, and its recurrent parent, bread wheat cv. BarNir, were investigated under four environments across 2 years—water-limited and well-watered conditions in a rain-protected screen-house (Year 1) and two commercial open field plots under ample precipitation (Year 2). NIL-7A-B-2 exhibited an advantage over BarNir in grain yield and biomass production under most environments. Further physiological analyses suggested that enhanced photosynthetic capacity and photochemistry combined with higher flag leaf area are among the factors underlying the improved productivity of NIL-7A-B-2. These were coupled with improved sink capacity in NIL-7A-B-2, manifested by greater yield components than its parental line. This study provides further support for our previous findings that introgression of wild emmer QTL alleles, using marker assisted selection, can enhance grain yield and biomass production across environments in domesticated wheat, thereby enriching the modern gene pool with essential diversity for the improvement of yield and drought resistance.

Cytokinin production by Pseudomonas fluorescens G20-18 determines biocontrol activity against Pseudomonas syringae in Arabidopsis.

Plant beneficial microbes mediate biocontrol of diseases by interfering with pathogens or via strengthening the host. Although phytohormones, including cytokinins, are known to regulate plant development and physiology as well as plant immunity, their production by microorganisms has not been considered as a biocontrol mechanism. Here we identify the ability of Pseudomonas fluorescens G20-18 to efficiently control P. syringae infection in Arabidopsis, allowing maintenance of tissue integrity and ultimately biomass yield. Microbial cytokinin production was identified as a key determinant for this biocontrol effect on the hemibiotrophic bacterial pathogen. While cytokinin-deficient loss-of-function mutants of G20-18 exhibit impaired biocontrol, functional complementation with cytokinin biosynthetic genes restores cytokinin-mediated biocontrol, which is correlated with differential cytokinin levels in planta. Arabidopsis mutant analyses revealed the necessity of functional plant cytokinin perception and salicylic acid-dependent defence signalling for this biocontrol mechanism. These results demonstrate microbial cytokinin production as a novel microbe-based, hormone-mediated concept of biocontrol. This mechanism provides a basis to potentially develop novel, integrated plant protection strategies combining promotion of growth, a favourable physiological status and activation of fine-tuned direct defence and abiotic stress resilience.

Genetic diversity and association mapping of iron and zinc concentrations in chickpea (Cicer arietinum L.).

Chickpea (Cicer arietinum L.) is the world's second most important pulse crop after common bean. Chickpea has historically been an important daily staple in the diet of millions of people, especially in the developing countries. Current chickpea breeding programs have mainly been directed toward high yield, biotic and abiotic stress resilience that has increased global production, but less attention has been directed toward improving micronutrient concentrations in seeds. In an effort to develop micronutrient-dense chickpea lines, a study to examine the variability and to identify SNP alleles associated with seed iron and zinc concentrations was conducted using 94 diverse accessions of chickpea. The results indicated that there is substantial variability present in chickpea germplasm for seed iron and zinc concentrations. In the current set of germplasm, zinc is negatively correlated with grain yield across all locations and years; whereas the negative correlation between iron and grain yield was only significant at the Elrose locality. Eight SNP loci associated with iron and (or) zinc concentrations in chickpea seeds were identified. One SNP located on chromosome 1 (chr1) is associated with both iron and zinc concentrations. On chr4, three SNPs associated with zinc concentration and two SNPs for iron concentration were identified. Two additional SNP loci, one on chr6 and the other on chr7, were also found to be associated with iron and zinc concentrations, respectively. The results show potential opportunity for molecular breeding for improvement of seed iron and zinc concentrations in chickpea.