Control of Bacterial Diseases of Banana Using CRISPR/Cas-Based Gene Editing

Twenty-eight years of GM Food and feed without harm: why not accept them?

Since the first genetically engineered or modified crops or organisms (GMO) were approved for commercial production in 1995, no new GMO has been proven to be a hazard or cause harm to human consumers. These modifications have improved crop efficiency, reduced losses to insect pests, reduced losses to viral and microbial plant pathogens and improved drought tolerance. A few have focused on nutritional improvements producing beta carotene in Golden Rice. Regulators in the United States and countries signing the CODEX Alimentarius and Cartagena Biosafety agreements have evaluated human and animal food safety considering potential risks of allergenicity, toxicity, nutritional and anti-nutritional risks. They consider risks for non-target organisms and the environment. There are no cases where post-market surveillance has uncovered harm to consumers or the environment including potential transfer of DNA from the GMO to non-target organisms. In fact, many GMOs have helped improve production, yield and reduced risks from chemical insecticides or fungicides. Yet there are generic calls to label foods containing any genetic modification as a GMO and refusing to allow GM events to be labeled as organic. Many African countries have accepted the Cartagena Protocol as a tool to keep GM events out of their countries while facing food insecurity. The rationale for those restrictions are not rational. Other issues related to genetic diversity, seed production and environmental safety must be addressed. What can be done to increase acceptance of safe and nutritious foods as the population increases, land for cultivation is reduced and energy costs soar?

Application of CRISPR/Cas-based gene-editing for developing better banana

Banana (Musa spp.), including plantain, is one of the major staple food and cash crops grown in over 140 countries in the subtropics and tropics, with around 153 million tons annual global production, feeding about 400 million people. Despite its widespread cultivation and adaptability to diverse environments, banana production faces significant challenges from pathogens and pests that often coexist within agricultural landscapes. Recent advancements in CRISPR/Cas-based gene editing offer transformative solutions to enhance banana resilience and productivity. Researchers at IITA, Kenya, have successfully employed gene editing to confer resistance to diseases such as banana Xanthomonas wilt (BXW) by targeting susceptibility genes and banana streak virus (BSV) by disrupting viral sequences. Other breakthroughs include the development of semi-dwarf plants, and increased β-carotene content. Additionally, non-browning banana have been developed to reduce food waste, with regulatory approval in the Philippines. The future prospects of gene editing in banana looks promising with CRISPR-based gene activation (CRISPRa) and inhibition (CRISPRi) techniques offering potential for improved disease resistance. The Cas-CLOVER system provides a precise alternative to CRISPR/Cas9, demonstrating success in generating gene-edited banana mutants. Integration of precision genetics with traditional breeding, and adopting transgene-free editing strategies, will be pivotal in harnessing the full potential of gene-edited banana. The future of crop gene editing holds exciting prospects for producing banana that thrives across diverse agroecological zones and offers superior nutritional value, ultimately benefiting farmers and consumers. This article highlights the pivotal role of CRISPR/Cas technology in advancing banana resilience, yield and nutritional quality, with significant implications for global food security.

Precision genetics tools for genetic improvement of banana

Banana is an important food security crop for millions of people in the tropics but it faces challenges from diseases and pests. Traditional breeding methods have limitations, prompting the exploration of precision genetic tools like genetic modification and genome editing. Extensive efforts using transgenic approaches have been made to develop improved banana varieties with resistance to banana Xanthomonas wilt, Fusarium wilt, and nematodes. However, these efforts should be extended for other pests, diseases, and abiotic stresses. The commercialization of transgenic crops still faces continuous challenges with regulatory and public acceptance. Genome editing, particularly CRISPR/Cas, offers precise modifications to the banana genome and has been successfully applied in the improvement of banana. Targeting specific genes can contribute to the development of improved banana varieties with enhanced resistance to various biotic and abiotic constraints. This review discusses recent advances in banana improvement achieved through genetic modification and genome editing.

Secondary Metabolites and Antioxidant Activity against Moko Disease as a Defense Mechanism of Musa spp. from the Ecuadorian Coast Area

The Musa spp. represents the most commonly produced, transitioned, and consumed fruit around the globe, with several important applications in the biotechnology, pharmaceutical, and food industries. Moko disease is produced by Ralstonia solanacearum-a factor with a high impact on all crops in Ecuador, representing one of the biggest phytosanitary problems. Four of the most common varieties of Musa spp. were tested to identify the metabolic reaction of plants facing Moko disease. The phenolic and flavonoid content has been evaluated as a defense system, and the α-diphenyl-α-picrylhydrazyl free-radical-scavenging method (DPPH), free-radical-scavenging activity (ABTS), ferric-reducing antioxidant power (FRAP) assays, and liquid chromatography and mass spectrometry (LC-MS) have been adapted to analyze the active compounds with the antioxidant capacity necessary to counteract the pathogenic attack. Our results indicate that all the studied varieties of Musa spp. react in the same way, such that the diseased samples showed a higher accumulation of secondary metabolites with antioxidant capacity compared with the healthy ones, with high active compound synthesis identified during the appearance of Moko disease symptoms. More than 40 compounds and their derivatives (from kaempferol and quercetin glycosides) with protective roles demonstrate the implication of the Musa spp. defense system against R. solanacearum infection.

Targeted knockout of early nodulin-like 3 (MusaENODL3) gene in banana reveals its function in resistance to Xanthomonas wilt disease

Nodulins and nodulin-like proteins play an essential role in the symbiotic associations between legumes and Rhizobium bacteria. Their role extends beyond the leguminous species, as numerous nodulin-like proteins, including early nodulin-like proteins (ENODL), have been identified in various non-leguminous plants, implying their involvement in functions beyond nodulation, such as nutrient transport and growth modulation. Some ENODL proteins have been associated with plant defense against pathogens, as evident in banana infected with Xanthomonas campestris pv. musacearum (Xcm) causing banana Xanthomonas wilt (BXW) disease. Nonetheless, the specific role of ENODL in plant defense remains to be fully elucidated. The MusaENODL3 gene was found to be repressed in BXW-resistant banana progenitor 'Musa balbisiana' and 20-fold upregulated in BXW-susceptible cultivar 'Gonja Manjaya' upon early infection with Xcm. To further unravel the role of the ENODL gene in disease resistance, the CRISPR/Cas9 system was employed to disrupt the MusaENODL3 gene in 'Gonja Manjaya' precisely. Analysis of the enodl3 edited events confirmed the accurate manipulation of the MusaENODL3 gene. Disease resistance and gene expression analysis demonstrated that editing the MusaENODL3 gene resulted in resistance to BXW disease, with 50% of the edited plants remaining asymptomatic. The identification and manipulation of the MusaENODL3 gene highlight its potential as a critical player in plant-pathogen interactions, offering new opportunities for enhancing disease resistance in crops like banana, an important staple food crop and source of income for resource-poor farmers in the tropics. This study provides the first evidence of the direct role of the ENODL3 gene in developing disease-resistant plants.

The crosstalk between SUMOylation and immune system in host-pathogen interactions

Pathogens can not only cause infectious diseases, immune system diseases, and chronic diseases, but also serve as potential triggers or initiators for certain tumors. They directly or indirectly damage human health and are one of the leading causes of global deaths. Small ubiquitin-like modifier (SUMO) modification, a type of protein post-translational modification (PTM) that occurs when SUMO groups bond covalently to particular lysine residues on substrate proteins, plays a crucial role in both innate and adaptive immunologic responses, as well as pathogen-host immune system crosstalk. SUMOylation participates in the host's defense against pathogens by regulating immune responses, while numerically vast and taxonomically diverse pathogens have evolved to exploit the cellular SUMO modification system to break through innate defenses. Here, we describe the characteristics and multiple functions of SUMOylation as a pivotal PTM mechanism, the tactics employed by various pathogens to counteract the immune system through targeting host SUMOylation, and the character of the SUMOylation system in the fight between pathogens and the host immune system. We have also included a summary of the potential anti-pathogen SUMO enzyme inhibitors. This review serves as a reference for basic research and clinical practice in the diagnosis, prognosis, and treatment of pathogenic microorganism-caused disorders.

CRISPR-Cas technology secures sustainability through its applications: a review in green biotechnology

The CRISPR-Cas system's applications in biotechnology offer a promising avenue for addressing pressing global challenges, such as climate change, environmental pollution, the energy crisis, and the food crisis, thereby advancing sustainability. The ever-growing demand for food due to the projected population of around 9.6 billion by 2050 requires innovation in agriculture. CRISPR-Cas technology emerges as a powerful solution, enhancing crop varieties, optimizing yields, and improving resilience to stressors. It offers multiple gene editing, base editing, and prime editing, surpassing conventional methods. CRISPR-Cas introduces disease and herbicide resistance, high-yielding, drought-tolerant, and water-efficient crops to address rising water utilization and to improve the efficiency of agricultural practices which promise food sustainability and revolutionize agriculture for the benefit of future generations. The application of CRISPR-Cas technology extends beyond agriculture to address environmental challenges. With the adverse impacts of climate change and pollution endangering ecosystems, there is a growing need for sustainable solutions. The technology's potential in carbon capture and reduction through bio-sequestration is a pivotal strategy for combating climate change. Genomic advancements allow for the development of genetically modified organisms, optimizing biofuel and biomaterial production, and contributing to a renewable and sustainable energy future. This study reviews the multifaceted applications of CRISPR-Cas technology in the agricultural and environmental fields and emphasizes its potential to secure a sustainable future.

Evolution of the WRKY66 Gene Family and Its Mutations Generated by the CRISPR/Cas9 System Increase the Sensitivity to Salt Stress in Arabidopsis

Group Ⅲ WRKY transcription factors (TFs) play pivotal roles in responding to the diverse abiotic stress and secondary metabolism of plants. However, the evolution and function of WRKY66 remains unclear. Here, WRKY66 homologs were traced back to the origin of terrestrial plants and found to have been subjected to both motifs' gain and loss, and purifying selection. A phylogenetic analysis showed that 145 WRKY66 genes could be divided into three main clades (Clade A-C). The substitution rate tests indicated that the WRKY66 lineage was significantly different from others. A sequence analysis displayed that the WRKY66 homologs had conserved WRKY and C2HC motifs with higher proportions of crucial amino acid residues in the average abundance. The AtWRKY66 is a nuclear protein, salt- and ABA- inducible transcription activator. Simultaneously, under salt stress and ABA treatments, the superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities, as well as the seed germination rates of Atwrky66-knockdown plants generated by the clustered, regularly interspaced, short palindromic repeats/CRISPR-associated 9 (CRISPR/Cas9) system, were all lower than those of wild type (WT) plants, but the relative electrolyte leakage (REL) was higher, indicating the increased sensitivities of the knockdown plants to the salt stress and ABA treatments. Moreover, RNA-seq and qRT-PCR analyses revealed that several regulatory genes in the ABA-mediated signaling pathway involved in stress response of the knockdown plants were significantly regulated, being evidenced by the more moderate expressions of the genes. Therefore, the AtWRKY66 likely acts as a positive regulator in the salt stress response, which may be involved in an ABA-mediated signaling pathway.

A Perspective Review on Understanding Drought Stress Tolerance in Wild Banana Genetic Resources of Northeast India

The enormous perennial monocotyledonous herb banana (Musa spp.), which includes dessert and cooking varieties, is found in more than 120 countries and is a member of the order Zingiberales and family Musaceae. The production of bananas requires a certain amount of precipitation throughout the year, and its scarcity reduces productivity in rain-fed banana-growing areas due to drought stress. To increase the tolerance of banana crops to drought stress, it is necessary to explore crop wild relatives (CWRs) of banana. Although molecular genetic pathways involved in drought stress tolerance of cultivated banana have been uncovered and understood with the introduction of high-throughput DNA sequencing technology, next-generation sequencing (NGS) techniques, and numerous "omics" tools, unfortunately, such approaches have not been thoroughly implemented to utilize the huge potential of wild genetic resources of banana. In India, the northeastern region has been reported to have the highest diversity and distribution of Musaceae, with more than 30 taxa, 19 of which are unique to the area, accounting for around 81% of all wild species. As a result, the area is regarded as one of the main locations of origin for the Musaceae family. The understanding of the response of the banana genotypes of northeastern India belonging to different genome groups to water deficit stress at the molecular level will be useful for developing and improving drought tolerance in commercial banana cultivars not only in India but also worldwide. Hence, in the present review, we discuss the studies conducted to observe the effect of drought stress on different banana species. Moreover, the article highlights the tools and techniques that have been used or that can be used for exploring and understanding the molecular basis of differentially regulated genes and their networks in different drought stress-tolerant banana genotypes of northeast India, especially wild types, for unraveling their potential novel traits and genes.

Exploring C-to-G and A-to-Y Base Editing in Rice by Using New Vector Tools

CRISPR/Cas9-based cytosine base editors (CBEs) and adenine base editors (ABEs) can efficiently mediate C-to-T/G-to-A and A-to-G/T-to-C substitutions, respectively; however, achieving base transversions (C-to-G/C-to-A and A-to-T/A-to-C) is challenging and has been rarely studied in plants. Here, we constructed new plant C-to-G base editors (CGBEs) and new A-to-Y (T/C) base editors and explored their base editing characteristics in rice. First, we fused the highly active cytidine deaminase evoFENRY and the PAM-relaxed Cas9-nickase variant Cas9n-NG with rice and human uracil DNA N-glycosylase (rUNG and hUNG), respectively, to construct CGBE-rUNG and CGBE-hUNG vector tools. The analysis of five NG-PAM target sites showed that these CGBEs achieved C-to-G conversions with monoallelic editing efficiencies of up to 27.3% in T₀ rice, with major byproducts being insertion/deletion mutations. Moreover, for the A-to-Y (C or T) editing test, we fused the highly active adenosine deaminase TadA8e and the Cas9-nickase variant SpGn (with NG-PAM) with Escherichia coli endonuclease V (EndoV) and human alkyladenine DNA glycosylase (hAAG), respectively, to generate ABE8e-EndoV and ABE8e-hAAG vectors. An assessment of five NG-PAM target sites showed that these two vectors could efficiently produce A-to-G substitutions in a narrow editing window; however, no A-to-Y editing was detected. Interestingly, the ABE8e-EndoV also generated precise small fragment deletions in the editing window from the 5′-deaminated A base to the SpGn cleavage site, suggesting its potential value in producing predictable small-fragment deletion mutations. Overall, we objectively evaluated the editing performance of CGBEs in rice, explored the possibility of A-to-Y editing, and developed a new ABE8e-EndoV tool, thus providing a valuable reference for improving and enriching base editing tools in plants.