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Sugars Will Eventually be Exported Transporters (SWEETs) are the novel sugar transporters widely distributed among living systems. SWEETs play a crucial role in various bio-physiological processes, viz., plant developmental, nectar secretion, pollen development, and regulation of biotic and abiotic stresses, in addition to their prime sugar-transporting activity. Thus, in-depth structural, evolutionary, and functional characterization of maize SWEET transporters was performed for their utility in maize improvement. The mining of SWEET genes in the latest maize genome release (v.5) showed an uneven distribution of 20 ZmSWEETs. The comprehensive structural analyses and docking of ZmSWEETs with four sugars, viz., fructose, galactose, glucose, and sucrose, revealed frequent amino acid residues forming hydrogen (asparagine, valine, serine) and hydrophobic (tryptophan, glycine, and phenylalanine) interactions. Evolutionary analyses of SWEETs showed a mixed lineage with 50-100 % commonality of ortho-groups and -sequences evolved under strong purifying selection (Ka/Ks 0.5). The duplication analysis showed non-functionalization (ZmSWEET18 in B73) and neo- and sub-functionalization (ZmSWEET3, ZmSWEET6, ZmSWEET9, ZmSWEET19, and ZmSWEET20) events in maize. Functional analyses of ZmSWEET genes through co-expression, in silico expression and qRT-PCR assays showed the relevance of ZmSWEETs expression in regulating drought, heat, and waterlogging stress tolerances in maize. The first ever ZmSWEET-regulatory network revealed 286 direct (ZmSWEET-TF: 140 ZmSWEET-miRNA: 146) and 1226 indirect (TF-TF: 597; TF-miRNA: 629) edges. The present investigation has given new insights into the complex transcriptional and post-transcriptional regulation and the regulatory and functional relevance of ZmSWEETs in assigning stress tolerance in maize.

In rice farming, the blast disease caused by Magnaporthe oryzae (T.T. Hebert) M.E. Barr. is one of the primary production constraints worldwide. The current blast management options such as blast-resistant varieties and spraying fungicides are neither durable nor commercially and environmentally compatible. In the present study, we investigated the antifungal and defense elicitor activity of potassium phosphite (Phi) against M. oryzae on elite rice cultivar BPT5204 (popularly known as Samba Mahsuri in India) and its transgenic rice variant (ptxD-OE) over-expressing a phosphite dehydrogenase enzyme. The Phi was evaluated both preventively and curatively on rice genotypes where the preventive spray of Phi outperformed the Phi curative application with significant reductions in both rice blast severity (35.67-60.49%) and incidence (22.27-53.25%). Moreover, the application of Phi increased the levels of photosynthetic pigments (Chlorophyll and Carotenoids) coupled with increased activity of defense enzymes (PAL, SOD, and APx). Besides, Phi application also induced the expression of defense-associated genes (OsCEBiP and OsPDF2.2) in the rice leaf. Furthermore, the Phi application reduced the reactive Malondialdehyde (lipid peroxidation) to minimize the cellular damage incited by Magnaporthe in rice. Overall, the present study showed the potential of Phi for blast suppression on rice as an alternative to the current excessive use of toxic fungicides.

Aluminium (Al) is one of the most abundant metals in earth crust, which becomes toxic to the plants growing in acidic soil. Phytohormones like ethylene, auxin, cytokinin, abscisic acid, jasmonic acid and gibberellic acid are known to play important role in regulating Al toxicity tolerance in plants. Exogenous applications of auxin, cytokinin and abscisic acid have shown significant effect on Al-induced root growth inhibition. Moreover, ethylene and cytokinin act synergistically with auxin in responding against Al toxicity. A number of studies showed that phytohormones play vital roles in controlling root responses to Al toxicity by modulating reactive oxygen species (ROS) signalling, cell wall modifications, organic acid exudation from roots and expression of Al responsive genes and transcription factors. This review provides a summary of recent studies related to involvement of phytohormone signalling and cross-talk with other pathways in regulating response against Al toxicity in plants.

Nutrient transporter genes could be a potential candidate for improving crop plants, with enhanced nutrient uptake leading to increased crop yield by providing tolerance against different biotic and abiotic stresses. The world's food supply is nearing a crisis in meeting the demands of an ever-growing global population, and an increase in both yield and nutrient value of major crops is vitally necessary to meet the increased population demand. Nutrients play an important role in plant metabolism as well as growth and development, and nutrient deficiency results in retarded plant growth and leads to reduced crop yield. A variety of cellular processes govern crop plant nutrient absorption from the soil. Among these, nutrient membrane transporters play an important role in the acquisition of nutrients from soil and transport of these nutrients to their target sites. In addition, as excess nutrient delivery has toxic effects on plant growth, these membrane transporters also play a significant role in the removal of excess nutrients in the crop plant. The key function provided by membrane transporters is the ability to supply the crop plant with an adequate level of tolerance against environmental stresses, such as soil acidity, alkalinity, salinity, drought, and pathogen attack. Membrane transporter genes have been utilized for the improvement of crop plants, with enhanced nutrient uptake leading to increased crop yield by providing tolerance against different biotic and abiotic stresses. Further understanding of the basic mechanisms of nutrient transport in crop plants could facilitate the advanced design of engineered plant crops to achieve increased yield and improve nutrient quality through the use of genetic technologies as well as molecular breeding. This review is focused on nutrient toxicity and tolerance mechanisms in crop plants to aid in understanding and addressing the anticipated global food demand.

In the present scenario, the two global issues are food security and climate change. These issues are due to a lethal combination of various factors, such as increasing world population, shrinking agricultural land, dwindling agricultural resources, and erratic weather patterns. All these factors are an indication of the looming food crisis, which will worsen due to global warming. Environmental changes, such as extremes of temperature, and erratic precipitation patterns negatively alter the plant physiology, metabolism, biochemistry, soil characteristics, and microbe abundance. As a result, a considerable burden is inflicted on each farmer’s spine as well as the field’s productivity. Therefore, to improve the food and nutritional security, the plant biologist and researchers are compelled to aim for quick, sustainable, and eco-friendly technologies that enhance “climate-resiliency” in crops under current agriculture practices. In this aspect, many biology-revolutionizing genome-editing approaches have come into existence since the year 2005. It includes multiple platforms such as clustered regularly interspaced short palindromic repeats (CRISPR/Cas9 and CRISPR/Cpf1), zinc finger nucleases (ZFNs), and transcription activator-like effector nucleases (TALENs). Because of the simplicity, high efficiency enabled precise modifications at any genomic loci-of-interest (native endogenous gene or cis/trans-gene insertion), ability to discover novel traits, and accelerate trait development, the plant scientists have created multiple “climate change-resilient crops” especially cereals within their labs. These edited plants have been modified in such a way that they can withstand a broad spectrum of abiotic stresses such as heat, cold, salinity, drought, flood/submergence, pollutants, as well as biotic pests, pathogens, and weeds. As a result, in this chapter, the focus is on enlisting all the successful reports related to the use of genome-editing tools in reshaping the cereals’ climate-resiliency.

With the exponential increase in the world’s human population, improving agricultural productivity is among the top of the researchers’ agendas till the 2050 deadline. One of the potential solutions to this global issue is genome editing because of the precision, fastness, and probably low cost involved compared to other traditional methods. It is in the spotlight especially from the last decade due to the discovery of sequence-specific-based nuclease technology including CRISPR/Cas9 tool. Initially, this tool was applied only in protoplasts and calli. However, due to the modifications in vectors, Cas9 variants, cassettes, cloning systems, multiplexing, and delivery methods, this platform has revolutionized the plant science field. It has been exploited in such a manner that about 16 crop plants have been already edited in the last few years. Out of all crops, most of the editing has been done in the case of rice (Oryza sativa L., Family: Poaceae), a cereal staple food. Therefore, in the current chapter, we have highlighted about the CRISPR/Cas9-edited rice for agronomic traits, stress tolerance/resistance, and biofortification. Additionally, we have presented an overview of various tools, databases, and commercial service providers devoted solely to CRISPR/Cas9 genome-editing technology.

Weeds, pests, and pathogens are among the pre-harvest constraints in rice farming across rice-growing countries. For weed management, manual weeding and herbicides are widely practiced. Among the herbicides, glyphosate [N-(phosphonomethyl) glycine] is a broad-spectrum systemic chemical extensively used in agriculture. Being a competitive structural analog to phosphoenolpyruvate, it selectively inhibits the conserved 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) enzyme required for the biosynthesis of aromatic amino acids and essential metabolites in eukaryotes and prokaryotes. In the present study, we investigated the antifungal and defense elicitor activity of glyphosate against Magnaporthe oryzae on transgenic-rice overexpressing a glyphosate-resistance OsEPSPS gene (T173I + P177S; TIPS OsmEPSPS) for blast disease management. The glyphosate foliar spray on OsmEPSPS transgenic rice lines showed both prophylactic and curative suppression of blast disease comparable to a blasticide, tricyclazole. The glyphosate displayed direct antifungal activity on Magnaporthe oryzae as well as enhanced the levels of antioxidant enzymes and photosynthetic pigments in rice. However, the genes associated with phytohormones-mediated defense (OsPAD4, OsNPR1.3, and OsFMO) and innate immunity pathway (OsCEBiP and OsCERK1) were found repressed upon glyphosate spray. Altogether, the current study is the first report highlighting the overexpression of a crop-specific TIPS mutation in conjugation with glyphosate application showing potential for blast disease management in rice cultivation.

Plants face a continuous threat of abiotic stresses under the changing environment. Because of climate change, water scarcity has been shown to be a significant environmental constraint on plant productivity. Droughts in particular have been shown to affect plant growth and development, lead to alteration in quality and quantity of crop production, and result in global food insecurity. Phytohormones are known to play critical roles in regulating diverse processes of plant adaption to a drought environment. They regulate cellular functions at molecular levels via various cell signaling. Among various phytohormones, abscisic acid (ABA) is known for its role in drought-stress tolerance in plants. Other phytohormones such as auxins, brassinosteroids (BRs), cytokinins (CK), ethylene (ET), gibberellins (GA), jasmonic acid (JA), and salicylic acid (SA) are also crucial in plant drought tolerance. Several plant growth-promoting microbes have been reported to enhance the phytohormone levels in plants to mitigate the negative effect of drought. However, the transgenic approach appears to be a boon to engineering the genes responsible for regulating phytohormones to develop a drought-tolerant trait. Expression analyses have revealed that genes encoding transcription factors such as bZIP11, DREB2, MYB14, MYB48, WRKY2, WRKY56, WRKY108715, and RD22 play a very crucial role in phytohormone mediated drought response. Furthermore, exogenous applications of phytohormones are shown to enhance endogenous phytohormones. This review highlights the most recent advancements in phytohormone-mediated drought tolerance in major crop plants.

Crop plants encounter a complex set of abiotic and biotic stresses very frequently. Abiotic stresses, being unavoidable, have major negative impact on crop production worldwide. These stresses such as inadequate and inconsistent rainfall, alkalinity, salinity, extreme temperature, and some other factors aren’t only limiting crop yield but also seem to be inevitably worsening. Considering present situation, it is imperative to switch to some more sophisticated techniques that shall combat abiotic environmental challenges and improve crop yield efficiently. Among these, seed priming is a commonly utilized technology for enhancing seed vigor and stress tolerance. Seed priming involves the attainment of a specific physiological state by synthetic or natural compounds. Crop plants raised from primed seeds exhibit instant cellular response against abiotic stresses. Primed seed acquire resistance through various cellular and metabolic pathways which involves cascades of signaling networks. Studies, till date, have confirmed that primed seeds have several advantages over traditionally used methods which include uniform germination, reduction in germination and emergence time, and broad range of tolerance against disease and environmental stresses. Seed priming methods are widely used as an emerging technology to produce tolerant crop varieties against abiotic stresses.

Asparagine is formed by two structurally distinct asparagine synthetases in prokaryotes. One is the ammonia-utilizing asparagine synthetase A (AsnA), and the other is asparagine synthetase B (AsnB) that uses glutamine or ammonia as a nitrogen source. In a previous investigation using sequence-based analysis, we had shown that Leishmania spp. possess asparagine-tRNA synthetase paralog asparagine synthetase A (LdASNA) that is ammonia-dependent. Here, we report the cloning, expression, and kinetic analysis of ASNA from Leishmania donovani. Interestingly, LdASNA was both ammonia- and glutamine-dependent. To study the physiological role of ASNA in Leishmania, gene deletion mutations were attempted via targeted gene replacement. Gene deletion of LdASNA showed a growth delay in mutants. However, chromosomal null mutants of LdASNA could not be obtained as the double transfectant mutants showed aneuploidy. These data suggest that LdASNA is essential for survival of the Leishmania parasite. LdASNA enzyme was recalcitrant toward crystallization so we instead crystallized and solved the atomic structure of its close homolog from Trypanosoma brucei (TbASNA) at 2.2 Å. A very significant conservation in active site residues is observed between TbASNA and Escherichia coli AsnA. It is evident that the absence of an LdASNA homolog from humans and its essentiality for the parasites make LdASNA a novel drug target.