Genetic engineering of crops: a ray of hope for enhanced food security

OsRuvBL1a DNA helicase boost salinity and drought tolerance in transgenic indica rice raised by in planta transformation

RuvBL, is a member of SF6 superfamily of helicases and is conserved among the various model systems. Recently, rice (Oryza sativa L.) homolog of RuvBL has been biochemically characterized for its ATPase and DNA helicase activities; however its involvement in stress has not been studied so far. Present investigation reports the detailed functional characterization of OsRuvBL under abiotic stresses through genetic engineering. An efficient Agrobacterium-mediated in planta transformation protocol was developed in indica rice to generate the transgenic lines and study was focused on optimization of factors to achieve maximum transformation efficiency. Overexpressing OsRuvBL1a transgenic lines showed enhanced tolerance under in vivo salinity stress as compared to WT plants. The physiological and biochemical analysis of the OsRuvBL1a transgenic lines showed better performance under salinity and drought stresses. Several stress responsive interacting partners of OsRuvBL1a were identified using Y2H system revealed to its role in stress tolerance. Functional mechanism for boosting stress tolerance by OsRuvBL1a has been proposed in this study. This integration of OsRuvBL1a gene in rice genome using in planta transformation method helped to achieve the abiotic stress resilient smart crop. This study is the first direct evidence to show the novel function of RuvBL in boosting abiotic stress tolerance in plants.

An overview: CRISPR/Cas-based gene editing for viral vaccine development

INTRODUCTION

: Gene-editing technology revolutionized vaccine manufacturing and offers a variety of benefits over traditional vaccinations, such as improved immune response, higher production rate, stability, precise immunogenic activity, and fewer adverse effects. The more recently discovered Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/associated protein 9 (Cas9) system has become the most widely utilized technology based on its efficiency, utility, flexibility, versatility, ease of use, and cheaper compared to other gene-editing techniques. Considering its wider scope for genomic modification, CRISPR/Cas9-based technology's potential is explored for vaccine development.

AREAS COVERED

: In this review, we will address the recent advances in the CRISPR/Cas system for the development of vaccines and viral vectors for delivery. In addition, we will discuss strategies for the development of the vaccine, as well as the limitations and future prospects of the CRISPR/Cas system.

EXPERT OPINION

: Human and animal viruses have been exposed to antiviral CRISPR/Cas9-based engineering to prevent infection, which uses knockout, knock-in, gene activation/deactivation, RNA targeting, and editing cell lines strategies for gene editing of viruses. Because of that CRISPR/Cas system is used to boost the vaccine production yield by removing unwanted genes that cause disease or are required for viral infection.

Establishment of a Novel and Efficient Agrobacterium-Mediated in Planta Transformation System for Passion Fruit (Passiflora edulis)

Passion fruit (Passiflora edulis) is an important fruit crop with high economic value. Genetic engineering plays an important role in crop improvement with desired traits and gene functional studies. The lack of a simple, efficient, and stable transformation system for passion fruit has greatly limited gene functional studies. In this study, a simple and efficient Agrobacterium-mediated in planta transformation system for passion fruit was established, using Agrobacterium virulent strain EHA105 harboring the binary vectors pCAMBIA1301 and pCAMBIA1302 with GUS and GFP reporter genes. The system requires less time and labor costs than conventional transformation systems, and no additional phytohormones and sterile conditions are required. Regeneration efficiency of 86% and transformation efficiency of 29% were achieved, when the wounds were wrapped with Parafilm and the plants were kept in darkness for 15 days. Approximately 75% of the regenerated plants had a single shoot and 26% multiple shoots. The transformation was confirmed at the DNA and RNA levels as well as by GUS staining and GFP fluorescent measurements. The developed protocol will contribute to the genetic improvement of passion fruit breeding.

The apple DNA-binding one zinc-finger protein MdDof54 promotes drought resistance

DNA-binding one zinc-finger (Dof) proteins constitute a family of transcription factors with a highly conserved Dof domain that contains a C2C2 zinc-finger motif. Although several studies have demonstrated that Dof proteins are involved in multiple plant processes, including development and stress resistance, the functions of these proteins in drought stress resistance are largely unknown. Here, we report the identification of the MdDof54 gene from apple and document its positive roles in apple drought resistance. After long-term drought stress, compared with nontransgenic plants, MdDof54 RNAi plants had significantly shorter heights and weaker root systems; the transgenic plants also had lower shoot and root hydraulic conductivity, as well as lower photosynthesis rates. By contrast, compared with nontransgenic plants, MdDof54-overexpressing plants had higher photosynthesis rates and shoot hydraulic conductivity under long-term drought stress. Moreover, compared with nontransgenic plants, MdDof54-overexpressing plants had higher survival percentages under short-term drought stress, whereas MdDof54 RNAi plants had lower survival percentages. MdDof54 RNAi plants showed significant downregulation of 99 genes and significant upregulation of 992 genes in response to drought, and 366 of these genes were responsive to drought. We used DAP-seq and ChIP-seq analyses to demonstrate that MdDof54 recognizes cis-elements that contain an AAAG motif. Taken together, our results provide new information on the functions of MdDof54 in plant drought stress resistance as well as resources for apple breeding aimed at the improvement of drought resistance.

SlHyPRP1 and DEA1, the multiple stress responsive eight-cysteine motif family genes of tomato (Solanum lycopersicum L.) are expressed tissue specifically, localize and interact at cytoplasm and plasma membrane in vivo

Owing to rapid global climate change, the occurrence of multiple abiotic stresses is known to influence the outburst of biotic stress factors which affects crop productivity. Therefore, it is essential to understand the molecular and cell biology of key genes associated with multiple stress responses in crop plants. SlHyPRP1 and DEA1, the members of eight-cysteine motif (8CM) family genes have been recently identified as putative regulators of multiple stress responses in tomato (Solanum lycopersicum L.). In order to gain deeper insight into cell and molecular biology of SlHyPRP1 and DEA1, we performed their expression analysis in three tomato cultivars and in vivo cell biological analysis. The semi-quantitative PCR and qRT-PCR results showed the higher expression of SlHyPRP1 and DEA1 in leaf, stem, flower and root tissues as compared to fruit and seed tissues in all three cultivars. The expression levels of SlHyPRP1 and DEA1 were found to be relatively higher in a wilt susceptible tomato cultivar (Arka Vikas) than a multiple disease resistant cultivar (Arka Abhed). In vivo cell biological analysis through Gateway cloning and Bi-FC assay revealed the predominant sub-cellular localization and strong protein-protein interaction of SlHyPRP1 and DEA1 at the cytoplasm and plasma membrane. Moreover, SlHyPRP1 showed in vivo interaction with stress responsive proteins WRKY3 and MST1. Our findings suggest that SlHyPRP1 with DEA1 are co-expressed with tissue specificity and might function together by association with WRKY3 and MST1 in plasma membrane for regulating multiple stress responses in the tomato plant.

The role of C2H2 zinc finger proteins in plant responses to abiotic stresses

Abiotic stresses are important factors affecting plant growth and development and limiting agricultural production worldwide. Plants have evolved complex regulatory mechanisms to respond and adapt to constantly changing environmental conditions. C2H2 zinc finger proteins form a relatively large family of transcriptional regulators in plants. Recent studies have revealed that C2H2 zinc finger proteins function as key transcriptional regulators in plant responses to a wide spectrum of stress conditions, including extreme temperatures, salinity, drought, oxidative stress, excessive light and silique shattering. Here, we summarize recent functional analysis on C2H2 zinc finger proteins in plant responses to abiotic stresses and discuss their roles as part of a large regulatory network in the perception and responses by plants to different environmental stimuli.

CRISPR/Cas approach: A new way of looking at plant-abiotic interactions

It is not the most grounded of the species that survive, nor the most shrewd, however one most receptive to change. Crop plants being sessile are subjected to various abiotic stresses resulting significant yield losses about an average of more than 50 percent, thus greatly threatening the global crop production. In this regard, plant breeding innovations and genetic engineering approaches have been used in the past for generating stress tolerant crop genotypes, but due to complex inheritance of abiotic stress tolerance these approaches are not enough to bring significant trait improvement and to guarantee world's future sustenance security. Although, RNA interference (RNAi) technology has been utilized amid the most recent decades to produce plants tolerant to environmental stress. But this technique ordinarily prompts to down-regulate as opposed to complete inhibition of target genes. Therefore, scientist/researchers were looking for techniques that should be efficient, precise and reliable as well as have potential to solve the issues experienced by previous approaches, and hence the CRISPR/Cas system came into spotlight. Although, only few studies using CRISPR/Cas approach for targeting abiotic stress tolerance related genes have been reported, but suggested its effective role for future applications in molecular breeding to improve abiotic stress tolerance. Hence, genome engineering via CRISPR-Cas system for targeted mutagenesis promise its immense potential in generating elite cultivars of crop plants with enhanced and durable climate resilience. Lastly, CRISPR-Cas will be future of crop breeding as well as to target minor gene variation of complex quantitative traits, and thus will be the key approach to release global hunger and maintain food security.

CRISPR/Cas9-Advancing Orthopoxvirus Genome Editing for Vaccine and Vector Development

The clustered regularly interspaced short palindromic repeat (CRISPR)/associated protein 9 (Cas9) technology is revolutionizing genome editing approaches. Its high efficiency, specificity, versatility, flexibility, simplicity and low cost have made the CRISPR/Cas9 system preferable to other guided site-specific nuclease-based systems such as TALENs (Transcription Activator-like Effector Nucleases) and ZFNs (Zinc Finger Nucleases) in genome editing of viruses. CRISPR/Cas9 is presently being applied in constructing viral mutants, preventing virus infections, eradicating proviral DNA, and inhibiting viral replication in infected cells. The successful adaptation of CRISPR/Cas9 to editing the genome of Vaccinia virus paves the way for its application in editing other vaccine/vector-relevant orthopoxvirus (OPXV) strains. Thus, CRISPR/Cas9 can be used to resolve some of the major hindrances to the development of OPXV-based recombinant vaccines and vectors, including sub-optimal immunogenicity; transgene and genome instability; reversion of attenuation; potential of spread of transgenes to wildtype strains and close contacts, which are important biosafety and risk assessment considerations. In this article, we review the published literature on the application of CRISPR/Cas9 in virus genome editing and discuss the potentials of CRISPR/Cas9 in advancing OPXV-based recombinant vaccines and vectors. We also discuss the application of CRISPR/Cas9 in combating viruses of clinical relevance, the limitations of CRISPR/Cas9 and the current strategies to overcome them.

Simultaneous Expression of PDH45 with EPSPS Gene Improves Salinity and Herbicide Tolerance in Transgenic Tobacco Plants

To cope with the problem of salinity- and weed-induced crop losses, a multi-stress tolerant trait is need of the hour but a combinatorial view of such traits is not yet explored. The overexpression of PDH45 (pea DNA helicase 45) and EPSPS (5-enoylpruvyl shikimate-3-phosphate synthase) genes have been reported to impart salinity and herbicide tolerance. Further, the understanding of mechanism and pathways utilized by PDH45 and EPSPS for salinity and herbicide tolerance will help to improve the crops of economical importance. In the present study, we have performed a comparative analysis of salinity and herbicide tolerance to check the biochemical parameters and antioxidant status of tobacco transgenic plants. Collectively, the results showed that PDH45 overexpressing transgenic lines display efficient tolerance to salinity stress, while PDH45+EPSPS transgenics showed tolerance to both the salinity and herbicide as compared to the control [wild type (WT) and vector control (VC)] plants. The activities of the components of enzymatic antioxidant machinery were observed to be higher in the transgenic plants indicating the presence of an efficient antioxidant defense system which helps to cope with the stress-induced oxidative-damages. Photosynthetic parameters also showed significant increase in PDH45 and PDH45+EPSPS overexpressing transgenic plants in comparison to WT, VC and EPSPS transgenic plants under salinity stress. Furthermore, PDH45 and PDH45+EPSPS synergistically modulate the jasmonic acid and salicylic acid mediated signaling pathways for combating salinity stress. The findings of our study suggest that pyramiding of the PDH45 gene with EPSPS gene renders host plants tolerant to salinity and herbicide by enhancing the antioxidant machinery thus photosynthesis.

Use of Reporter Genes in the Generation of Vaccinia Virus-Derived Vectors

Vaccinia virus (VACV) is one of the most extensively-studied viruses of the Poxviridae family. It is easy to genetically modify, so it has become a key tool for many applications. In this context, reporter genes facilitate the study of the role of foreign genes introduced into the genome of VACV. In this review, we describe the type of reporter genes that have been used to generate reporter-expressing VACV and the applications of the recombinant viruses obtained. Reporter-expressing VACV are currently employed in basic and immunology research, in the development of vaccines and cancer treatment.

Emerging Importance of Helicases in Plant Stress Tolerance: Characterization of Oryza sativa Repair Helicase XPB2 Promoter and Its Functional Validation in Tobacco under Multiple Stresses

Genetic material always remains at the risk of spontaneous or induced damage which challenges the normal functioning of DNA molecule, thus, DNA repair is vital to protect the organisms against genetic damage. Helicases, the unique molecular motors, are emerged as prospective molecules to engineer stress tolerance in plants and are involved in nucleic acid metabolism including DNA repair. The repair helicase, XPB is an evolutionary conserved protein present in different organisms, including plants. Availability of few efficient promoters for gene expression in plants provoked us to study the promoter of XPB for better understanding of gene regulation under stress conditions. Here, we report the in silico analysis of novel stress inducible promoter of Oryza sativa XPB2 (OsXPB2). The in vivo validation of functionality/activity of OsXPB2 promoter under abiotic and hormonal stress conditions was performed by Agrobacterium-mediated transient assay in tobacco leaves using OsXPB2::GUS chimeric construct. The present research revealed that OsXPB2 promoter contains cis-elements accounting for various abiotic stresses (salt, dehydration, or cold) and hormone (Auxin, ABA, or MeJA) induced GUS expression/activity in the promoter-reporter assay. The promoter region of OsXPB2 contains CACG, GTAACG, CACGTG, CGTCA CCGCCGCGCT cis acting-elements which are reported to be salt, dehydration, cold, MeJA, or ABA responsive, respectively. Functional analysis was done by Agrobacterium-mediated transient assay using agroinfiltration in tobacco leaves, followed by GUS staining and fluorescence quantitative analyses. The results revealed high induction of GUS activity under multiple abiotic stresses as compared to mock treated control. The present findings suggest that OsXPB2 promoter is a multi-stress inducible promoter and has potential applications in sustainable crop production under abiotic stresses by regulating desirable pattern of gene expression.