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CRISPR-Cas technologies for precision genome editing in plants: advances, applications, and future perspectives.

Developing climate-smart crops with enhanced crop productivity, nutritional quality, resistance to biological and environmental stressors is vital for global food security. While hybrid breeding forms the cornerstone of modern crop improvement, conventional breeding approaches are limited by genetic barriers and prolonged breeding cycles. CRISPR-Cas based genome editing has revolutionized plant biology by allowing precise, efficient, and multiplex genetic modifications. This review provides a comprehensive synthesis of a recent advances in CRISPR-Cas technologies and their strategic applications in crop genetics and hybrid breeding. We summarize major genome-editing strategies, including gene knock-out, base editing (BE), knock-in, gene replacement, epigenome editing, and transcriptional regulation. Furthermore, we contrast stable, transient, and DNA-free delivery systems, highlighting ribonucleoprotein (RNP)-mediated delivery for minimizing off-target effects and avoiding transgene integration. We showcase how these technologies accelerate hybrid breeding by engineering male sterility systems, fixing heterosis, and generating high-throughput mutant libraries for trait discovery. Finally, we synthesize major bottlenecks in tissue culture-independent transformation and delivery systems, while outlining how emerging paradigms like de novo domestication and synthetic biology will shape the future of climate-resilient agriculture.

CRISPR/Cas

Quantifying Protein-Nucleic Acid Interactions for Engineering Useful CRISPR-Cas9 Genome-Editing Variants.

Numerous high-specificity Cas9 variants have been engineered for precision genome editing. These variants typically harbor multiple mutations designed to alter the Cas9-single guide RNA (sgRNA)-DNA complex interactions for reduced off-target cleavage. By dissecting the contributions of individual mutations, we attempt to derive principles for designing high-specificity Cas9 variants. Here, we computationally modeled the specificity harnessing mutations of the widely used Cas9 isolated from Streptococcus pyogenes (SpCas9) and investigated their individual mutational effects. We quantified the mutational effects in terms of energy and contact changes by comparing the wild-type and mutant structures. We found that these mutations disrupt the protein-protein or protein-DNA contacts within the Cas9-sgRNA-DNA complex. We also identified additional impacted amino acid sites via energy changes that constitute the structural microenvironment encompassing the focal mutation, giving insights into how the mutations contribute to the high-specificity phenotype of SpCas9. Our method outlines a strategy to evaluate mutational effects that can facilitate rational design for Cas9 optimization.

Gene Editing

Genetically Modified and Gene-Edited Organisms-Objectives, Public Perception and Applications.

Genetic modification and genome editing have become important tools in agriculture, animal production, biotechnology, and human medicine, but their safety and societal acceptance remain subjects of debate. This review examines genetically modified (GM) and gene-edited organisms, distinguishing transgenesis from precision genome editing technologies, including CRISPR/Cas9, base editing, and prime editing. Representative applications in crops, livestock, pharmaceutical production, and xenotransplantation are discussed, together with their regulatory framework and public perception. Current scientific assessments indicate that approved GM foods are not inherently more hazardous to human health than their conventional counterparts when evaluated case by case. Potential benefits include improved nutritional quality, biofortification, disease resistance, increased agricultural efficiency, production of therapeutic proteins, and applications in animal health and medicine. Possible concerns include allergenicity, toxicity, unintended genetic or phenotypic effects, altered nutritional composition, environmental consequences, animal welfare issues, and uncertainties associated with long-term or large-scale deployment. Public acceptance varies substantially according to geographical region, application, cultural and ethical considerations, regulatory environment, scientific literacy, and institutional trust. Overall, GM and gene-edited organisms should not be considered a homogeneous category. Their benefits, risks, and societal acceptability depend on the specific organism, genetic modification, intended trait, and context of use, supporting a balanced, evidence-based, and case-specific approach.

acceptance

Development of a highly efficient prime editing platform for cucurbits enables breeding of multi-disease-resistant cucumber.

The prime editing (PE) system is a precise genome editing technology that works efficiently in monocots; however, its application is limited by low editing efficiency in dicots, particularly Cucurbitaceae and Solanaceae plants. Here, we first significantly improved the transformation efficiency by introducing spectinomycin in cucurbits, then used the tomato elongation factor 1-alpha (SlEF1α) promoter to enhance PE protein expression, and incorporated the Csy4 ribonuclease to process pegRNAs, collectively addressing multiple constraints limiting PE efficiency in cucurbits. The optimized PE systems, particularly Csy4-PE6d, achieved an average desired editing frequency of 80.83% at targeted loci in cucumber via stable genetic transformation, with frequencies reaching up to 100% at certain sites. Moreover, Csy4-PE6d generated homozygous edits in 36.43% of transgenic lines and demonstrated robust editing activity in melon, pumpkin, and potato. Using the Csy4-PE6d tool, we generated heritable edited cucumber lines with dual resistance to bacterial angular leaf spot and downy mildew by targeting the CsSGR gene. Collectively, this optimized system substantially enhances PE efficiency in Cucurbit crops, providing an effective solution to common challenges such as low editing efficiency and limited heritability in these species.

Disease Resistance

Computational modeling of human genetic variants in mice.

Mouse models represent a powerful platform to study genes and variants associated with human diseases. While genome editing technologies have increased the rate and precision of model development, predicting and installing specific types of mutations in mice that mimic the native human genetic context is complicated. Computational tools can identify and align orthologous wild-type genetic sequences from different species; however, predictive modeling and engineering of equivalent mouse variants that mirror the nucleotide and/or polypeptide change effects of human variants remains challenging. Here, we present H2M (human-to-mouse), a computational pipeline to analyze human genetic variation data to systematically model and predict the functional consequences of equivalent mouse variants. We show that H2M can integrate mouse-to-human and paralog-to-paralog variant mapping analyses with precision genome editing pipelines to devise strategies tailored to model specific variants in mice. We leveraged these analyses to establish a database containing > 3 million human-mouse equivalent mutation pairs, as well as in silico-designed base and prime editing libraries to engineer 4,944 recurrent variant pairs. Using H2M, we also found that predicted pathogenicity and immunogenicity scores were highly correlated between human-mouse variant pairs, suggesting that variants with similar sequence change effects may also exhibit broad interspecies functional conservation. Overall, H2M fills a gap in the field by establishing a robust and versatile computational framework to identify and model homologous variants across species while providing key experimental resources to augment functional genetics and precision medicine applications. The H2M database (including software package and documentation) can be accessed at https://human2mouse.com.

Journal Article

Enhancing CRISPR-Cas12a base editing in plants with LbCas12a variants and introns.

Cytosine base editors (CBEs) and adenine base editors (ABEs) are powerful tools for precise genome editing in plants. Conventionally, such base editors are built upon the CRISPR-Cas9 systems where Cas9 nickases are used. To expand the base editing scope and minimize off-target effects, base editors derived from the CRISPR-Cas12a systems are desired. However, the use of deactivated Cas12a (dCas12a) in such base editors constrains the editing activity, preventing the wide use of Cas12a base editors for plant research and trait development. In this study, we demonstrate the use of an ABE based on the efficient LbCas12a-RRV variant to introduce herbicide-resistant mutations in OsACCase in rice. To improve Cas12a CBEs and ABEs, we inserted introns into the coding sequence of dLbCas12a-RRV. This intron-containing Cas12a-CBE shows substantial improvement in editing efficiency in rice, compared to the intron-less counterparts. By contrast, the improvement of ABE with the intron-containing dLbCas12a-RRV is very limited, partly due to the already high baseline editing efficiency of the intron-less dLbCas12a-RRV ABE. Testing of these base editors in poplar shows elevated C-to-T base editing by dLbCas12a-RRV-intron-CBE. For A-to-G editing, ABEs built upon dLbCas12a-RV and dLbCas12a-RRV variants showed significant improvement over ABEs derived from wild-type LbCas12a and the ttLbCas12a variant. The addition of introns to dLbCas12a-RRV does not further improve the base editing efficiency. With whole genome sequencing in rice, we evaluated genome editing specificities with these improved Cas12a base editors. Our analyses show that both intron-containing Cas12a CBE and ABE barely introduce guide RNA-dependent off-target mutations. However, they can generate guide RNA-independent off-target mutations, which are likely attributed to the high enzymatic activities of the deaminases. Collectively, our study demonstrates the successful use of a Cas12a base editor for trait development and reports improved Cas12a CBEs and ABEs for precise base editing in plants.

Oryza

RNA-DNA hybrid binding domain broadens the editing window of base editors.

Adenine base editors (ABEs) and cytosine base editors (CBEs) are prominent tools for precise genome editing but are hindered by limited editing activity at positions proximal to the protospacer adjacent motif (PAM). This study investigates the potential of enhancing base editors editing activity by fusing them with RNA-DNA hybrid binding domains (RHBDs). Specifically, fusing ABE8e with the RHBD of Homo sapiens RNaseH1 (RHBD1) significantly increased A-to-G editing efficiency in the PAM-proximal region (A9-A15) by up to 3.5-fold, while reducing off-target cytosine editing. Additionally, RHBD1 is compatible with ABEmax, BE4max, and dual base editor (eA&C-BEmax), enhancing their editing activity at the PAM-proximal bases. Notably, RHBD1-fused BE4max led to a 3.1-fold improvement in C-to-T editing efficiency at PAM-proximal region (C9-C12). Furthermore, we demonstrated that RHBD1-fused ABE8e could effectively edit disease-related single nucleotide variations (SNVs) in human cells and validated its efficacy in adult mouse liver. These findings highlight the significance of the RHBD in expanding editing window and the applicability of base editors for gene therapy and disease modeling.

Gene Editing

Engineering recombination machinery facilitates the construction of yeast cell factories.

Advances in genome editing have been promoted by programmable nucleases like CRISPR-Cas9, which triggers endogenous DNA repair mechanisms by inducing double-strand break (DSB). Cellular responses to DSBs are governed by competing repair pathways: error-prone non-homologous end joining (NHEJ) and high-fidelity homologous recombination (HR). This review systematically compares the molecular mechanisms and key regulators of NHEJ and HR, with a focus on recent breakthroughs in recombination engineering in non-conventional yeasts. These advances address challenges in precise genome editing, enabling robust metabolic engineering of yeast cell factories for sustainable bioproduction.

Metabolic Engineering

Molecular Bases and Genetic Design of Rice Disease Resistance for Optimized Yield and Sustainable Agriculture.

Rice diseases continue to undermine yield stability and threaten the sustainability of rice production. The central challenge is therefore not simply to maximize immune activation, but to identify genetic interventions that remain effective across diverse pathogen races and environmental conditions without imposing excessive penalties on growth or yield. Here, we synthesize the molecular basis of rice immunity from a design-oriented perspective. We first examine cell-surface pattern-recognition receptors and intracellular nucleotide-binding leucine-rich repeat receptors, and then assess the shared signaling hubs and defence outputs that connect pathogen perception to antimicrobial responses. Rather than treating these components as equivalent breeding targets, we compare their translational potential according to resistance spectrum, anticipated durability, tunability, pleiotropic risk, and the strength of field evidence. We further discuss breeding strategies based on receptor engineering, editing of susceptibility genes and cis-regulatory elements, post-translational motif engineering, pathogen-inducible and upstream open reading frame-mediated regulation, resistance-gene stacking and artificial intelligence-assisted prediction. We argue that rational resistance design in rice should move beyond constitutive immune activation toward allele-specific, quantitative, spatially restricted and infection-responsive regulation. Integrating mechanistic insights with precision genome editing, accelerated breeding and responsible deployment offers a practical route to durable, yield-compatible disease resistance while reducing dependence on chemical control.

breeding strategy

Minimizing Off-Target Effects of CRISPR-Cas9 With Optimized sgRNA: Evaluation of Efficiency and Specificity in the Tumor Protein 53 (TP53) Region.

CRISPR-Cas9 is a widely used genetic tool with therapeutic potential in molecular biology. CRISPR-Cas9 enables precise genome editing by its ability to target specific DNA sequence. After off-target and on-target regions are identified, CRISPR-Cas9 is applied to these regions based on the match between the guide RNA (gRNA) and target DNA sequence. This study points to the off-target impact of mismatches between the gRNA and target DNA on exon regions of the TP53 gene, which are involved in regulating multiple genes and cellular functions. Off-target positions are typically evaluated using scoring methods. In this study, we have used latent class analysis to reveal subclasses of off-target positions. Thus, we have created the levels of off-target positions and evaluated the effects of mismatching positions within these classes using machine learning classifiers. The results revealed that mismatching positions could be categorized into three levels: low, middle, and high off-target positions. We have improved a computational framework to minimize off-target effects and to identify the PAM sequences in the gRNA design. Thus, carefully designed gRNAs will ensure that desired genetic edits are performed and target variants are achieved. This work will avail the future research aimed at optimizing genome editing by customizing CRISPR-Cas9 to target specific protospacer DNA through gRNA.

CRISPR-Cas Systems

Preparation of high-purity RNPs of CRISPR-based DNA base editors.

Since their introduction, CRISPR-based DNA base editors (BEs) have become essential in the field of precision genome editing, revolutionizing the correction of pathogenic SNPs for both basic research and therapeutic applications. As this technology advances, more laboratories are implementing these tools into their workflow. The delivery of BEs as BE-guide RNA complexes (RNPs), rather than as mRNA or plasmids, has been shown to exhibit lower off-target effects, establishing it as the preferred method of delivery. However, there are no protocols describing in detail how to obtain high-purity and highly active BE RNPs. Here, we offer a comprehensive guide for the expression, purification, RNP reconstitution, and in vitro activity assessment of TadA-based BEs. The protocol includes guidance on performing activity assays using commercial denaturing gels, which is convenient and uses standard molecular biology equipment. This allows for rapid quality control testing of reconstituted BE RNPs prior to more expensive and time-consuming in vivo genome editing experiments. Overall, this protocol aims to empower more laboratories to generate tailored BE RNPs for diverse in vitro and in vivo applications.

Gene Editing

Charting the development and engineering of CRISPR base editors: lessons and inspirations.

CRISPR base editors (BEs) have introduced a new chapter in precise genome editing. The brief but fruitful history of BE development documents many case studies that not only lay the foundation of base-editing technology but are also instrumental to future protein engineering efforts. In this review, we summarize the development and engineering of various BEs with a focus on recent progress. These include traditional cytosine and adenine base editors (CBEs and ABEs), novel TadA-derived CBEs, transversion BEs, dual BEs, and CRISPR-free BEs. We discuss each aspect of the workflow and highlight the successes and challenges encountered in the engineering process.

Gene Editing

CRISPGen: A deep generative framework for multi-objective CRISPR/Cas9 guide RNA design via Conditional Latent Diffusion and Dual-Critic Reinforcement Learning.

MOTIVATION: The CRISPR-Cas9 system offers transformative potential for precision genome editing, yet its clinical translation remains constrained by the risk of unintended off-target double-strand breaks. While current discriminative models excel at evaluating pre-specified candidate guides, resolving the fundamental antagonism between on-target cleavage efficiency and off-target specificity within a fixed sequence search space remains a major challenge. RESULTS: We present CRISPGen, a unified deep generative framework that reframes sgRNA design as a multi-objective constrained sequence synthesis problem. It integrates (i) DNABERT-2 genomic-language embeddings, (ii) a conditional latent diffusion generator conditioned on a user-specified on-target efficiency target, and (iii) a dual-critic reinforcement-learning (RL) stage that couples a frozen on-target efficiency critic with a cross-attention off-target discriminator (validation Pearson R=0.8157) trained on a unified corpus of experimental off-target events from six detection platforms. Across 1000 generated sgRNAs, CRISPGen reduces the mean off-target discriminator score by 99.7% relative to the pre-RL baseline and, under an exhaustive whole-genome screen of all 302,631,056 NGG PAM sites in GRCh38, yields zero perfect-match and only 55 one-mismatch genomic hits. We further show, transparently, that the internal on-target critic saturates under RL optimization - an instance of Goodhart's Law - and therefore assess on-target viability using an independent external CRISPRon screen (mean 47.10/100). Repeating the RL fine-tuning stage under three random seeds (with the diffusion generator, DNABERT-2 embeddings, and off-target discriminator held fixed) yields a stable operating point across seeds. Full diversity, per-mismatch, and reproducibility statistics are reported in the Results. AVAILABILITY: Source code is available at https://github.com/malekpouri/CRISPGen; the pre-trained checkpoints and the 3,000,000-sequence library are hosted on Hugging Face (https://huggingface.co/malekpouri/CRISPGen-Checkpoints) and archived on Zenodo under DOI 10.5281/zenodo.21428641.

CRISPR-Cas9

Interfering with DNA repair pathways to enhance CRISPR-Cas9-mediated homology-directed repair in a chelicerate genetic model.

The two-spotted spider mite, Tetranychus urticae, is a major pest and an emerging genetic model. Recent CRISPR-Cas9 advances, especially the SYNCAS method for maternal delivery of Cas9 ribonucleoproteins, have enabled precise genome editing in this and other difficult-to-transform arthropods. Yet SYNCAS-mediated knockins vary in efficiency, possibly due to competition between DNA repair pathways, whose mechanisms in T. urticae and other chelicerates remain unknown. Here, we provide the first functional analysis of double-strand break repair in a chelicerate. Loss of DNA polymerase theta (Polθ) redirects repair almost entirely toward homology-directed repair, whereas absence of Ligase IV has no detectable impact. Using a reporter assay targeting phytoene desaturase, we demonstrate that Polθ-deficient strains enhance incorporation of repair templates, even when mutations are distant from the cut site. Also, insertion of larger fragments is improved. Finally, disrupting Polθ imposes only a modest fitness cost, highlighting its value for future genome engineering in this species.

Acari

Cellular function of the GndA microprotein during heat shock.

Over the past 15 years, hundreds of previously undiscovered bacterial small open reading frames (sORFs) encoding microproteins of fewer than fifty amino acids have been identified. Biological functions have been ascribed to an increasing number of microproteins from intergenic regions and small RNAs, and many play integral roles in bacterial stress responses. However, despite numbering in the dozens in Escherichia coli, and hundreds in humans, same-strand frameshifted sORFs that internally overlap protein coding sequences remain understudied. To provide insight into nested genes, we characterized GndA, a frameshifted 36-amino acid microprotein nested within the 6-phosphogluconate dehydrogenase (6PGD) coding sequence. Using precise genome editing, we demonstrate independent contributions of GndA and 6PGD to cell growth at high temperature. GndA associates with membrane-associated complexes associated with electron transport and ATP generation, and supports ATP homeostasis during heat shock. Functional characterization of GndA thus adds to the catalog of bacterial microproteins that function in stress responses, while providing clear genetic evidence for the importance of an overlapping gene to cellular fitness.

6PGD

Plant cis-regulatory grammar: Decoding the multidimensional code of transcriptional regulation for programmable crop engineering.

Cis-regulatory elements (CREs) orchestrate the spatiotemporal precision of gene expression that underlies plant development, adaptation, and domestication. Decoding the cis-regulatory grammar of plant genomes remains a central challenge in modern biology, with profound implications for programmable crop engineering. Here, recent conceptual and technological advances are synthesized to reshape our understanding of plant CREs. This review first argues that CRE function is not only an intrinsic property of DNA sequence alone but also emerges from a multidimensional context, including chromatin accessibility, histone modifications, three-dimensional genome topology, and cell type-specific regulatory landscapes. Furthermore, the convergence of single-cell epigenomics, high-throughput functional assays, and CRISPR-based dissection has begun to unravel this contextual grammar, revealing the computational principles governing transcriptional regulation. Critically, we propose that artificial intelligence (AI) platforms are catalyzing an ongoing transition from descriptive discovery to predictive engineering, wherein these platforms outperform natural evolution in designing synthetic CREs. Finally, a roadmap is outlined toward a plant regulatory grammar foundation model, which will enable truly predictive engineering of gene expression when fine-tuned for specific tasks. Collectively, the integration of single-cell resolution maps, precise genome editing, AI-driven design, and regulatory-compliant delivery systems promises to transform our ability to reprogram plant gene regulation for next-generation agriculture, bridging the gap between foundational regulatory biology and tangible crop improvement.

artificial intelligence

Pleiotropic mutation in a tendril TCP gene underlies the yield-enhancing multiple-flowering trait in summer squash (Cucurbita pepo).

Crop yield is a focal point in plant breeding. Regulation of lateral budding through apical dominance was a central target of crop domestication, directly affecting crop production. The young fruits of Cucurbita pepo, summer squash, are produced on plants characterized by apical dominance and differentiation of a single flower bud per leaf axil. A single recessive mutation, mf, results in differentiation of more than one flower per leaf axil, thereby directly increasing production because of the continual day-to-day harvest of the summer squash crop. Positional cloning of the Cucurbita pepo mf (Cpmf) gene denoted a frameshift mutation in a TCP transcription factor, Cp4.1LG13g07780, as causative for the increase in axillary flowering. Cpmf is an ortholog of a tendril-development TCP gene in other cucurbits, and likewise, the recessive allele of Cpmf is associated with distorted tendril development. Gene function is context dependent, and we propose that multiple flowering is a unique pleiotropic attribute of mutation in a tendril-development gene of C. pepo. Characterization of a C. pepo collection confirmed a significant association of the Cpmf mutation with multiple flowering and showed that the mutant allele is absent in ancestral C. pepo and one of its two cultivated subspecies. The beneficial mutation occurred and was selected after the domestication of the other subspecies, during its cultivation for young fruit production. We demonstrate the discovery of a causative yield-increasing sequence variant and its practical utilization in breeding. Our findings provide a molecular target for creation of high-yielding, multiple-flowering summer squash cultivars through marker-assisted breeding or precise genome editing.

Cucurbita