CRISPR/Cas9-mediated homology donor repair base editing system to confer herbicide resistance in maize (Zea mays L.).

Weed infestation is a significant concern to crop yield loss, globally. The potent broad-spectrum glyphosate (N-phosphomethyl-glycine) has a widely utilized herbicide, acting on the shikimic acid pathway within chloroplast by inhibiting 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). This crucial enzyme plays a vital role in aromatic amino acid synthesis. Repurposing of CRISPR/Cas9-mediated gene-editing was the inflection point for generating novel crop germplasm with diverse genetic variations in essential agronomic traits, achieved through the introduction of nucleotide substitutions at target sites within the native genes, and subsequent induction of indels through error-prone non-homologous end-joining DNA repair mechanisms. Here, we describe the development of efficient herbicide-resistant maize lines by using CRISPR/Cas9 mediated site-specific native ZmEPSPS gene fragment replacement via knock-out of conserved region followed by knock-in of desired homologous donor repair (HDR-GATIPS-mZmEPSPS) with triple amino acid substitution. The novel triple substitution conferred high herbicide tolerance in edited maize plants. Transgene-free progeny harbouring the triple amino acid substitutions revealed agronomic performances similar to that of wild-type plants, suggesting that the GATIPS-mZmEPSPS allele substitutions are crucial for developing elite maize varieties with significantly enhanced glyphosate resistance. Furthermore, the aromatic amino acid contents in edited maize lines were significantly higher than in wild-type plants. The present study describing the introduction of site-specific CRISPR/Cas9- GATIPS mutations in the ZmEPSPS gene via genome editing has immense potential for higher tolerance to glyphosate with no yield penalty in maize.

Functional characterization of novel mutations in the conserved region of EPSPS for herbicide resistance in pigeonpea: structure-based coherent design.

Prospectively, agroecosystems for the growth of crops provide the potential fertile, productive, and tropical environment which attracts infestation by weedy plant species that compete with the primary crop plants. Infestation by weed is a major biotic stress factor faced by pigeonpea that hampers the productivity of the crop. In the modern era with the development of chemicals the problem of weed infestation is dealt with armours called herbicides. The most widely utilized, post-emergent, broad-spectrum herbicide has an essential active ingredient called glyphosate. Glyphosate mechanistically inhibits a chloroplastic enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) by competitively interacting with the PEP binding site which hinders the shikimate pathway and the production of essential aromatic amino acids (Phe, Tyr, Trp) and other secondary metabolites in plants. Moreover, herbicide spray for weed management is lethal to both the primary crop and the weeds. Therefore, it is critical to develop herbicide-resistant crops for field purposes to reduce the associated yield and economic losses. In this study, the in-silico analysis drove the selection and validation of the point mutations in the conserved region of the EPSPS gene, which confers efficient herbicide resistance to mutated-CcEPSPS enzyme along with the retention of the normal enzyme function. An optimized in-silico validation of the target mutation before the development of the genome-edited resistant plant lines is a prerequisite for testing their efficacy as a proof of concept. We validated the combination of GATIPS mutation for its no-cost effect at the enzyme level via molecular dynamic (MD) simulation.Communicated by Ramaswamy H. Sarma.

HIGHLIGHTSWeed infestation is a major biotic stress factor and a consistent problem in agriculture.Development of glyphosate-resistant mutation is crucial to minimize the yield loss in agriculturally or nutritionally important crops for field application.Present in-silico approach is a proof-of-concept for validation of the selected glyphosate-resistant mutations.The current study has validated the combination of GATIPS mutation for its glyphosate-resistant phenotype and no negative cost effect at the enzyme simulation level.

CRISPR/Cas9-mediated homology donor repair base editing confers glyphosate resistance to rice (Oryza sativa L.).

Globally, CRISPR-Cas9-based genome editing has ushered in a novel era of crop advancements. Weeds pose serious a threat to rice crop productivity. Among the numerous herbicides, glyphosate [N-(phosphonomethyl)-glycine] has been employed as a post-emergent, broad-spectrum herbicide that represses the shikimate pathway via inhibition of EPSPS (5'-enolpyruvylshikimate-3-phosphate synthase) enzyme in chloroplasts. Here, we describe the development of glyphosate-resistant rice lines by site-specific amino acid substitutions (G172A, T173I, and P177S: GATIPS-mOsEPSPS) and modification of phosphoenolpyruvate-binding site in the native OsEPSPS gene employing fragment knockout and knock-in of homology donor repair (HDR) template harboring desired mutations through CRISPR-Cas9-based genome editing. The indigenously designed two-sgRNA OsEPSPS-NICTK-1_pCRISPR-Cas9 construct harboring rice codon-optimized SpCas9 along with OsEPSPS-HDR template was transformed into rice. Stable homozygous T2 edited rice lines revealed significantly high degree of glyphosate-resistance both in vitro (4 mM/L) and field conditions (6 ml/L; Roundup Ready) in contrast to wild type (WT). Edited T2 rice lines (ER1-6) with enhanced glyphosate resistance revealed lower levels of endogenous shikimate (14.5-fold) in contrast to treated WT but quite similar to WT. ER1-6 lines exhibited increased aromatic amino acid contents (Phe, two-fold; Trp, 2.5-fold; and Tyr, two-fold) than WT. Interestingly, glyphosate-resistant Cas9-free EL1-6 rice lines displayed a significant increment in grain yield (20%-22%) in comparison to WT. Together, results highlighted that the efficacy of GATIPS mutations in OsEPSPS has tremendously contributed in glyphosate resistance (foliar spray of 6 ml/L), enhanced aromatic amino acids, and improved grain yields in rice. These results ensure a novel strategy for weed management without yield penalties, with a higher probability of commercial release.

Efficacy and safety of 250 mg versus 500 mg oral terbinafine in the treatment of tinea corporis and cruris: A randomised, assessor-blinded comparative study.

Background Though higher doses of terbinafine are often prescribed to treat dermatophyte infections, it is unknown if such doses are more effective than the conventional dose because comparative data are unavailable. Aim To compare the efficacy and safety of a once-daily dose of oral terbinafine 250 mg with 500 mg along with topical clotrimazole in the treatment of tinea infections. Methods A randomised, assessor-blinded, comparative study was carried out. Each group of subjects were administered either 250 mg or 500 mg oral terbinafine once daily for four weeks, along with topical clotrimazole. Clinical improvement was assessed after two weeks and again after four weeks from treatment initiation. Result A total of 60 patients with tinea corporis and cruris were randomised into two groups receiving either 250 mg (group A) or 500 mg (group B) oral terbinafine, along with clotrimazole cream in both groups. Baseline clinical parameters such as lesional activity (papules, vesicles and pustules), degree of erythema, scaling and severity of itching were comparable between both treatment arms. At the first and second follow-ups, no significant differences were found in the clinical parameters between the two groups. At the end of two weeks 13.8% of group A and 14.3% of group B and after 4 weeks 25.9% of group A and 33.3% of group B participants became KOH negative (P = 1.00 and 0.76, respectively). No significant difference in culture negativity was reported at the end of therapy (four weeks) between the two treatment arms (P = 0.78). Overall cure rates were 20% and 33.3% in the two treatment arms respectively at the end of the study (P = 0.82). Conclusion Oral terbinafine 250 mg daily yielded a poor cure rate in tinea cruris and corporis after 4 weeks of treatment and an increased dose of 500 mg did not have any additional benefit.

De novo genome assembly of rice bean (Vigna umbellata) - A nominated nutritionally rich future crop reveals novel insights into flowering potential, habit, and palatability centric - traits for efficient domestication.

Rice bean is a less-known underutilized legume crop with a high nutritional value among members of the Vigna family. As an initiative to compose rice bean (Vigna umbellata) genomic resource, the size of 414 mega-base pairs with an estimated identification of 31,276 high confidence index genes via 15,521 scaffolds generated from Illumina and PacBio platform 30X coverage data has achieved 96.08% functional coverage data from Illumina and PacBio platform. Rice bean genome assembly was found to be exquisitely close to Vigna angularis (experimental control/outgroup), Vigna radiata, and Vigna unguiculata, however, Vigna angularis being the closest. The assembled genome was further aligned with 31 leguminous plants (13 complete genomes and 18 partial genomes), by collinearity block mapping. Further, we predicted similar discriminant results by complete coding sequence (CDS) alignment. In contrast, 17 medically influential genomes from the National Institute of General Medical Sciences-National Institutes of Health NIGMS-NIH, when compared to rice bean assembly for LCB clusters, led to the identification of more than 18,000 genes from the entire selected medicinal genomes. Empirical construction of all genome comparisons revealed symplesiomorphic character in turn uncovering the lineage of genetic and functional features of rice beans. Significantly, we found deserving late-flowering genes, palatably indexed uncommon genes that regulate various metabolite pathways, related to abiotic and biotic stress pathways and those that are specific to photoperiod and disease resistance and so on. Therefore, the findings from this report address the genomic value of rice bean to be escalated via breeding by allied and applied approaches.

Fine-tuning the transcriptional regulatory model of adaptation response to phosphate stress in maize (Zea mays L.).

The post green revolution agriculture is based on generous application of fertilizers and high-yielding genotypes that are suited for such high input regimes. Cereals, like maize (Zea mays L.) are capable of utilizing less than 20% of the applied inorganic phosphate (Pi) - a non-renewable fertilizer resource. A greater understanding of the molecular mechanisms underlying the acquisition, transportation and utilization of Pi may lead to engineering genotypes with high phosphorus use efficiency. In this study, we carried out functional domain similarity analysis, promoter analysis and comparative transcriptional expression profiling of 12 selected Pi responsive genes in the Pi stress tolerant maize inbred line HKI-163 under sufficient and deficient Pi conditions. Pi starvation led to significant increase in root length; marked proliferation of root hairs and lesser number of crown roots. Eleven genes were significantly up or down regulated in Pi deficient condition. The putative acid phosphatase, ZmACP5 expression was up regulated by 162.81 and 74.40 fold in root and leaf tissues, respectively. The RNase, ZmRNS1 showed 115 fold up regulation in roots under Pi deprivation. Among the two putative high affinity Pi transporters ZmPht1;4 was found specific to root, whereas ZmPht2 was found to be up regulated in both root and leaf tissues. The genes involved in Pi homeostasis pathway (ZmSIZ1, SPX1 and Pho2) were up regulated in root and leaf. In light of the expression profiling of selected regulatory genes, an updated model of transcriptional regulation under Pi starvation in maize has been presented. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-022-01155-x.

Phylogenetic and modelling analysis of purple acid phosphatase 18 (SiPAP18) from Setaria italica.

Purple acid phosphatases belong to metallo-phosphatase family. Intracellular phosphatases are crucial for phosphorus (P) distribution in the cell and are highly induced in phosphorus-deprived conditions in the soil. Disparate PAP isoforms exist within discrete subcellular compartments in Setaria italica and their expression in P deprived conditions fosters phosphorus amelioration. We isolated the SiPAP18 gene and developed the homology SiPAP18 protein model based on the crystal structure of the Kidney bean PvPAP (PDB ID: 2QFP) as template (sequence similarity 42.7%) using Modeller 9.12 with adequate validation. Structure model analysis shows the significance of five conserved signatures with seven metal-paired amino acid residues during P-deprivation induced phosphorus amelioration.

Revisiting CRISPR/Cas-mediated crop improvement: Special focus on nutrition.

Genome editing (GE) technology has emerged as a multifaceted strategy that instantaneously popularised the mechanism to modify the genetic constitution of an organism. The clustered regularly interspaced short palindromic repeat (CRISPR) and CRISPR-associated (Cas) protein-based genome editing (CRISPR/Cas) approach has huge potential for efficacious editing of genomes of numerous organisms. This framework has demonstrated to be more economical in contrast to mega-nucleases, zinc-finger nucleases (ZFNs), and transcription activator-like effector nucleases (TALENs) for its flexibility, versatility, and potency. The advent of sequence-specific nucleases (SSNs) allowed the precise induction of double-strand breaks (DSBs) into the genome, ensuring desired alterations through non-homologous end-joining (NHEJ) or homology-directed repair (HDR) pathways. Researchers have utilized CRISPR/Cas-mediated genome alterations across crop varieties to generate desirable characteristics for yield enhancement, enriched nutritional quality, and stressresistance. Here, we highlighted the recent progress in the area of nutritional improvement of crops via the CRISPR/Cas-based tools for fundamental plant research and crop genetic advancements. Application of this genome editing aids in unraveling the basic biology facts in plants supplemented by the incorporation of genome-wide association studies, artificial intelligence, and various bioinformatic frameworks, thereby providing futuristic model studies and their affirmations. Strategies for reducing the 'off-target' effects and the societal approval of genome-modified crops developed via this modern biotechnological approach have been reviewed.

Data Mining by Pluralistic Approach on CRISPR Gene Editing in Plants.

Genome engineering by site-specific nucleases enables reverse genetics and targeted editing of genomes in an efficacious manner. Contemporary revolutionized progress in targeted-genome engineering technologies based on Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-related RNA-guided endonucleases facilitate coherent interrogation of crop genome function. Evolved as an innate component of the adaptive immune response in bacterial and archaeal systems, CRISPR/Cas system is now identified as a versatile molecular tool that ensures specific and targeted genome modification in plants. Applications of this genome redaction tool-kit include somatic genome editing, rectification of genetic disorders or gene therapy, treatment of infectious diseases, generation of animal models, and crop improvement. We review the utilization of these synthetic nucleases as precision, targeted-genome editing platforms with the inherent potential to accentuate basic science "strengths and shortcomings" of gene function, complement plant breeding techniques for crop improvement, and charter a knowledge base for effective use of editing technology for ever-increasing agricultural demands. Furthermore, the emerging importance of Cpf1, Cas9 nickase, C2c2, as well as other innovative candidates that may prove more effective in driving novel applications in crops are also discussed. The mined data has been prepared as a library and opened for public use at www.lipre.org.