Mutagenesis-based plant breeding approaches and genome engineering: A review focused on tomato

Screening and metabolic analysis of high-efficiency molluscicidal bacteria based on atmospheric and room temperature plasma mutagenesis

Oncomelania hupensis is the only intermediate host of Schistosoma japonicum, highlighting the need for developing low-toxicity, efficient, and economical molluscicides to control schistosomiasis transmission and prevalence. This study screened for effective molluscicides using O. hupensis in an immersion-based biological assay. Bsp dustable powder (DP) emerged as the most effective molluscicide among seven microbial pesticide samples tested. The dominant strain, designated 3-4, was isolated and identified as Bacillus subtilis using 16S rDNA gene sequencing. Following atmospheric and room temperature plasma (ARTP) mutagenesis, a mutant strain library containing 214 strains of bacteria was obtained. Most of the 139 mutant strains showed no significant difference compared with parental strain and 60 strains showed a decrease. Meanwhile, 15 mutant strains with higher molluscicidal effects were obtained. ARTP-129 and ARTP-154, exhibiting the highest positive mutation rates, demonstrated a 64.51 % increase in mortality compared to the parental strain 3-4. Metabolomic analysis revealed that the mutant strains may alter molluscicidal toxicity by regulating the synthesis pathways of metabolites such as l-pyroglutamic acid (PGA). These findings suggest the potential of ARTP mutagenesis for developing novel and effective molluscicides for schistosomiasis control.

Updates on the Regulatory Framework of Edited Organisms in Brazil: A Molecular Revolution in Brazilian Agribusiness

Genome editing technologies have revolutionized the production of microorganisms, plants, and animals with phenotypes of interest to agriculture. Editing previously sequenced genomes allows for the punctual, discreet, precise, and accurate alteration of DNA for genetic analysis, genotyping, and phenotyping, as well as the production of edited organisms for academic and industrial purposes, among many other objectives. In this context, genome editing technologies have been causing a revolution in Brazilian agriculture. Thanks to the publication of Normative Resolution No. 16 (in Portuguese Resolução Normativa No. 16-RN16) in 2018, Brazilian regulatory authorities have adapted to the new genetic manipulation technologies available to the scientific community. This review aims to describe the effects of updates to the regulatory framework for edited organisms in Brazil and to point out their impacts on research and development of emerging technologies in the Brazilian agricultural sector. The implementation of RN16 rationalized the regulatory aspects regarding the production, manipulation, exploration and commercial release of edited organisms and led to the faster, cheaper and safer obtaining of edited technologies, which are more productive and better adapted to different environmental conditions in Brazil.

Multi-omics analysis reveals the mechanism for galactose metabolism in mutant Streptococcus thermophilus IMAU20551Y

Streptococcus thermophilus (S. thermophilus) is a species widely used in the dairy industry to accelerate the acidification rate and improve the texture and flavour characteristics of dairy products. However, most S. thermophilus have galactose-negative (Gal-) phenotypes, which can lead to accumulation of free galactose in fermented dairy products. In a previous study, a mutant of S. thermophilus IMAU20551Y was obtained by N-methyl-N'-nitro-N-nitrosoguanidine (NTG) mutagenesis in which key enzymes related to galactose metabolism were significantly changed compared with the wild type. β-galactosidase and galactokinase activity were higher in the mutant while glucokinase and pyruvate kinase activities were significantly decreased compared with the wild type. In this study, the ability of the mutant to metabolize galactose was verified by high performance liquid chromatography (HPLC), and the mechanism for enhanced galactose metabolism elucidated by multi-omics analysis. HPLC analysis showed that accumulation of galactose in milk fermented by mutant S. thermophilus IMAU20551Y was reduced by 41.4%, compared with the wild type. Although no mutations in gene sequences associated with galactose metabolism were detected by genome sequencing, transcriptomic data showed up-regulation in expression of galM, galK, galT, galE (associated with the Leloir pathway) and LacI family transcriptional regulator GalR, resulting in enhanced galactose metabolism in the mutant. This study provides a reference for genetic engineering modification of galactose-positive (Gal+) S. thermophilus, which is expected to be used as a starter for the production of low galactose fermented dairy products.

A simple, cost-effective, and efficient method for screening CRISPR/Cas9 mutants in plants

The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)-mediated genome editing system is widely used for targeted mutagenesis in a growing number of plant species. To streamline the screening process for mutants, especially those generated from low-efficiency editing events, there is a need for a rapid, cost-effective, and efficient method. Although several screening methods have been developed to process initial samples, these methods often tend to be time-consuming, expensive, or inefficient when dealing with larger sample sizes. Here we describe a simple, rapid, low-cost, and sensitive screening method for screening CRISPR/Cas9 mutants called PCR-Bsl I-associated analysis (PCR-BAA). This method requires only standard PCR and Bsl I restriction enzyme digestion, as well as agarose gel electrophoresis analysis. This method is particularly well suited for the efficient screening of mutants from larger populations of transformants. The simplicity, low cost, and high sensitivity of the PCR-BAA method make it particularly suitable for rapid screening of CRISPR/Cas9-induced mutants, especially those from low-efficiency editing events.

CRISPR-Cas9: Unraveling Genetic Secrets to Enhance Floral and Fruit Traits in Tomato

Tomato, a globally consumed vegetable, possesses vast genetic diversity, making it suitable for genetic manipulation using various genetic improvement techniques. Tomatoes are grown extensively for their market value and health benefits, primarily contributed by enhanced yield and nutritional value respectively, influenced by floral and fruit traits. Floral morphology is maintained by genes involved in meristem size control, regulation of inflorescence transition, and pollen development. SP (SELF-PRUNING) and SP5G (SELF-PRUNING 5G) determine growth habit and flowering time. RIN (RIPENING INHIBITOR) and PG (POLYGALACTURONASE) are responsible for the shelf life of fruits. In addition to this, nutrition-enriched tomatoes have been developed in recent times. In this review, we comprehensively discuss the major genes influencing floral morphology, flowering time, fruit size, fruit shape, shelf life, and nutritional value, ultimately resulting in enhanced yield. Additionally, we address the advances in CRISPR/Cas9 applied for the genetic improvement of tomatoes along with prospects of areas in which research development in terms of tomato genetic improvement has to be advanced.

Development and Characterization of a New TILLING Population for Forward and Reverse Genetics in Barley (Hordeum vulgare L.)

Mutagenesis is an important tool in crop improvement and free of the regulatory restrictions imposed on genetically modified organisms. Barley (Hordeum vulgare L.) is a diploid species with a genome smaller than those of other members of the Triticeae crops, making it an attractive model for genetic studies in Triticeae crops. In this study, we report an ethyl methane sulfonate (EMS)-mutagenized population in the Chinese barley landrace TX9425, which is tolerant to both abiotic and biotic stress. A TILLING (Targeting Induced Locus Lesion in Genomes) population consisting of 2000 M2 lines was also constructed based on the CEL I enzyme with subsequent polyacrylamide electrophoresis, which decreased the cost and labor investment. The mutant phenotypes of the M2 and M3 generations were scored and revealed the presence of a wide spectrum of morphological diversity. The population was evaluated by screening for induced mutations in five genes of interest. A detailed analysis was performed for the HvGLR3.5 gene and three mutations were identified by screening in 2000 M2 lines. Two of three mutations displayed tuft and yellow striped leaves compared to the wild type. Altogether, our study shows the efficiency of screening and the great potential of the new TILLING population for genetic studies in the barley crop model system.

Induced genetic diversity through mutagenesis in wheat gene pool and significant use of SCoT markers to underpin key agronomic traits

BACKGROUND

This research explores the efficacy of mutagenesis, specifically using sodium azide (SA) and hydrazine hydrate (HZ) treatments, to introduce genetic diversity and enhance traits in three wheat (Triticum aestivum L.) genotypes. The experiment entails subjecting the seeds to different doses of SA and HZ and cultivating them in the field for two consecutive generations: M1 (first generation) and M2 (second generation). We then employed selective breeding techniques with Start Codon Targeted (SCoT) markers to select traits within the wheat gene pool. Also, the correlation between SCoT markers and specific agronomic traits provides insights into the genetic mechanisms underlying mutagenesis-induced changes in wheat.

RESULTS

In the study, eleven genotypes were derived from parent varieties Sids1, Sids12, and Giza 168, and eight mutant genotypes were selected from the M1 generation and further cultivated to establish the M2 generation. The results revealed that various morphological and agronomical characteristics, such as plant height, spikes per plant, spike length, spikelet per spike, grains per spikelet, and 100-grain weight, showed increases in different genotypes from M1 to M2. SCoT markers were employed to assess genetic diversity among the eleven genotypes. The bioinformatics analysis identified a correlation between SCoT markers and the transcription factors ABSCISIC ACID INSENSITIVE3 (ABI3) and VIVIPAROUS1 (VP1), crucial for plant development, growth, and stress adaptation. A comprehensive examination of genetic distance and the function identification of gene-associated SCoT markers may provide valuable insights into the mechanisms by which SA and HZ act as mutagens, enhancing wheat agronomic qualities.

CONCLUSIONS

This study demonstrates the effective use of SA and HZ treatments to induce gene diversity through mutagenesis in the wheat gene pool, resulting in the enhancement of agronomic traits, as revealed by SCoT markers. The significant improvements in morphological and agronomical characteristics highlight the potential of mutagenesis techniques for crop improvement. These findings offer valuable information for breeders to develop effective breeding programs to enhance wheat quality and resilience through increased genetic diversity.

Gene-Based Developments in Improving Quality of Tomato: Focus on Firmness, Shelf Life, and Pre- and Post-Harvest Stress Adaptations

Tomato (Solanum lycopersicum) is a widely consumed vegetable crop with significant economic and nutritional importance. This review paper discusses the recent advancements in gene-based approaches to enhance the quality of tomatoes, particularly focusing on firmness, shelf life, and adaptations to pre- and post-harvest stresses. Utilizing genetic engineering techniques, such as Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated proteins 9 (CRISPR/Cas9) and Transcription Activator-like Effector Nucleases (TALENs), researchers have made remarkable progress in developing tomatoes with improved traits that address key challenges faced during cultivation, storage, and transportation. We further highlighted the potential of genetic modifications in enhancing tomato firmness, thereby reducing post-harvest losses and improving consumer satisfaction. Furthermore, strategies to extend tomato shelf life through genetic interventions are discussed, emphasizing the importance of maintaining quality and freshness for sustainable food supply chains. Furthermore, the review delves into the ways in which gene-based adaptations can bolster tomatoes against environmental stresses, pests, and diseases, thereby enhancing crop resilience and ensuring stable yields. Emphasizing these crucial facets, this review highlights the essential contribution of genetic advancements in transforming tomato production, elevating quality standards, and promoting the sustainability of tomato cultivation practices.