Modification of Fatty Acid Profile and Oil Contents Using Gene Editing in Oilseed Crops for a Changing Climate

Mutation breeding based on various chemical and physical mutagens induces and disrupts non-target loci. Hence, large populations were required for visual screening, but desired plants were rare and it was a further laborious task to identify desirable mutants. Generated mutant had high defect due to non-targeted mutation, with poor agronomic performance. Mutation techniques were augmented by targeted induced local lesions in genome (TILLING) facilitating the selection of desirable germplasm. On the other hand, gene editing through CRISPR/Cas9 allows knocking down genes for site-directed mutation. This handy technique has been exploited for the modification of fatty acid profile. High oleic acid genetic stocks were obtained in a broad range of crops. Moreover, genes involved in the accumulation of undesirable seed components such as starch, polysaccharide, and flavors were knocked down to enhance seed quality, which helps to improve oil contents and reduces the anti-nutritional component.

Genetic modification of the ant Lasius niger using CRISPR-Cas9 technology

CRISPR-Cas9 has become one of the most prominent gene editing tools available and it has been utilized in various organisms from bacteria to fungi, plants, and animals. In this study, we developed a CRISPR-Cas9 protocol for the black garden ant Lasius niger, a common and easily available study species for lab and field experiments. To create indel mutations using CRISPR-Cas9 in L. niger, we targeted three different locations in a well-studied eye pigmentation gene cinnabar, generating several mutations that disrupt the ommochrome biosynthesis pathway and result in the lack of the pigment and therefore, abnormal eye coloration in adult workers. We also developed a protocol to collect L. niger eggs, inject them with CRISPR-Cas9 construct, and rear the eggs into mature adult workers with the assistance of nursing workers. We demonstrated for the first time in L. niger that CRISPR-Cas9 is an excellent tool to create targeted mutations for this species. Our protocol can be referred to when developing similar studies for other species of ants and eusocial insects.

Gamma irradiation-induced variability in morpho-agronomic and oil quality traits of Mentha piperita L

PURPOSE

To develop elite mutant in Mentha piperita having morphotype and oil content of Mentha arvensis, and oil quality of M. piperita.

MATERIALS AND METHODS

The dormant runner of menthol rich genotype MPK-5 were subjected to different doses of γ- irradiation (10, 20, 30, 50, 70, 90, and 110 Gy) at a dose rate of 55 Gy/min to induce the genetic variability for herb and oil yield as well as oil quality. A wide spectrum of variability for agro-morphological traits, herb yield, and quality profile was observed among the mutants.

RESULTS

The developed and selected superior mutants viz. MPK-5(1) and MPK-5(3) have a mean herb yield potential of 23.923 and 21.503 Kg/9 m²; mean oil yield of 92.953 and 80.047 ml/plot; mean menthol content of 69.012% and 69.160% with mean menthofuran content of 1.554% and 0.531%, respectively.

CONCLUSIONS

Mutational breeding through γ- irradiation is considered complementary to the conventional breeding method, to broaden the spectrum of genetic variability. The developed and selected mutants namely viz. MPK-5(1) and MPK-5(3) identified as promising mutants, based on herb yield, oil yield, and essential oil quality, could be used as a parental line for exploitation in hybridization program/recombinant breeding.

Transcriptome sequencing reveals hotspot mutation regions and dwarfing mechanisms in wheat mutants induced by γ-ray irradiation and EMS

Induced mutation is an important approach for creating novel plant germplasms. The introduction of dwarf or semi-dwarf genes into wheat has led to great advancements in yield improvement. In this study, four elite dwarf wheat mutants, named dm1-dm4, induced from γ-ray irradiation or ethyl methanesulfonate (EMS) mutagenesis, were used to identify transcriptome variations and dwarfing mechanisms. The results showed that the hotspot regions of mutations distributed on the chromosomes were consistent among the four mutant lines and these regions were mainly located around the 50, 360 and 400 Mb positions of chromosome 1A and the distal regions of chromosomes 2A and 2BL. Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses suggested that 'protein processing in endoplasmic reticulum' was the most common significantly enriched pathway based on the differentially expressed genes (DEGs) between wildtype (WT) and the mutants. Notably, 18 out of 20 genes involved in this process encode heat shock proteins (HSPs). The results implied that HSPs might participate in wheat dwarfism response and function in the dwarfism process through protein folding and/or degradation. Moreover, seven genes in dm4 involved in modulating auxin levels were down-regulated and dm4 was more sensitive to auxin treatment compared with WT, indicating the important roles of auxin in regulation of dwarf phenotype in dm4. This study not only identified transcriptome sequence variation induced by physical and chemical mutagenesis but also revealed potential dwarfing mechanisms in the wheat mutant lines.

Heritable Genomic Fragment Deletions and Small Indels in the Putative ENGase Gene Induced by CRISPR/Cas9 in Barley

Targeted genome editing with the CRISPR/Cas9 system has been used extensively for the selective mutation of plant genes. Here we used CRISPR/Cas9 to disrupt the putative barley (Hordeum vulgare cv. "Golden Promise") endo-N-acetyl-β-D-glucosaminidase (ENGase) gene. Five single guide RNAs (sgRNAs) were designed for different target sites in the upstream part of the ENGase coding region. Targeted fragment deletions were induced by co-bombarding selected combinations of sgRNA with wild-type cas9 using separate plasmids, or by co-infection with separate Agrobacterium tumefaciens cultures. Genotype screening was carried out in the primary transformants (T0) and their T1 progeny to confirm the presence of site-specific small insertions and deletions (indels) and genomic fragment deletions between pairs of targets. Cas9-induced mutations were observed in 78% of the plants, a higher efficiency than previously reported in barley. Notably, there were differences in performance among the five sgRNAs. The induced indels and fragment deletions were transmitted to the T1 generation, and transgene free (sgRNA:cas9 negative) genome-edited homozygous ENGase knock outs were identified among the T1 progeny. We have therefore demonstrated that mutant barley lines with a disrupted endogenous ENGase and defined fragment deletions can be produced efficiently using the CRISPR/Cas9 system even when this requires co-transformation with multiple plasmids by bombardment or Agrobacterium-mediated transformation. We confirm the specificity and heritability of the mutations and the ability to efficiently generate homozygous mutant T1 plants.

Chemical Mutagenesis of Seed and Vegetatively Propagated Plants Using EMS

Chemical mutagenesis provides an inexpensive and straightforward way to generate a high density of novel nucleotide diversity in the genomes of plants and animals. Mutagenesis therefore can be used for functional genomic studies and also for plant breeding. The most commonly used chemical mutagen in plants is ethyl methanesulfonate (EMS). EMS has been shown to induce primarily single base point mutations. Hundreds to thousands of heritable mutations can be induced in a single plant line. A relatively small number of plants, therefore, are needed to produce populations harboring deleterious alleles in most genes. EMS mutagenized plant populations can be screened phenotypically (forward-genetics), or mutations in genes can be identified in advance of phenotypic characterization (reverse-genetics). Reverse-genetics using chemically induced mutations is known as Targeting Induced Local Lesions IN Genomes (TILLING). This unit gives information on EMS treatment of seed and vegetative propagules. © 2016 by John Wiley & Sons, Inc.

Mutagenic effects induced by the attack of NO2 radical to the guanine-cytosine base pair

We investigate the attack of the nitrogen dioxide radical (NO^•₂) to the guanine—cytosine (GC) base pair and the subsequent tautomeric reactions able to induce mutations, by means of density functional theory (DFT) calculations. The conducted simulations allow us to identify the most reactive sites of the GC base pair. Indeed, the computed relative energies demonstrate that the addition of the NO^•₂ radical to the C8 position of the guanine base forms to the most stable adduct. Although the initial adducts might evolve to non-canonical structures via inter-base hydrogen bonds rearrangements, the probability for the proton exchange to occur lies in the same range as that observed for undamaged DNA. As a result, tautomeric errors in NO₂-attacked DNA arises at the same rate as in canonical DNA, with no macroscopic impact on the overall stability of DNA. The potential mutagenic effects of the GC–NO^•₂ radical adducts likely involve side reactions, e.g., the GC deprotonation to the solvent, rather than proton exchange between guanine and cytosine basis.