Roman A. Komakhin

Storage of potato tubers intended for further processing is complicated by their cold-induced sweetening (CIS). Enzymatic hydrolysis of sucrose into glucose and fructose occurs at low temperatures. The resulting high hexose content adversely affects the quality of processed potato products such as chips and fries and promotes the formation of acrylamide, which is a neurotoxin and carcinogen. During CIS, sucrose hydrolysis is catalyzed by vacuolar invertase encoded by the StPain-1 gene. Previous studies have shown that suppression of the enzyme activity confers potato resistance to CIS without reducing the nutritional value of tubers. In this study, CRISPR/Cas9 technology was used to generate Solanum tuberosum L. cv. Fritella plants with a knockout of StPain-1 . Two binary vectors based on pKSE401 were constructed (Vector A and Vector B), each carrying two gRNAs targeting exon 1 (sgRNA-P1.A or sgRNA-P1.B) and exon 3 (sgRNA-P3.A or sgRNA-P3.B). Editing efficiency with each gRNA was evaluated through next-generation sequencing (NGS). Transformation with Vector A produced 48 transformants, 22 of which carried knockouts in all StPain-1 alleles. Transformation with Vector B yielded 26 transformants, including 10 plants with complete StPain-1 knockout. Chips made from tubers of nine edited Fritella plants demonstrated reduced vacuolar invertase activity: chips from StPain -1 knockout lines were lighter compared to the non-edited control sample. Quantitative assessment of glucose, fructose, and sucrose levels, as well as StPain-1 mRNA expression in tubers of four selected transformants (two per vector), confirmed enzyme inactivation. The resulting plants exhibit increased resistance to cold-induced sweetening and can be used as a promising source of nonfunctional StPain-1 alleles for breeding new potato varieties.

Generation of state-of-the-art highly productive cabbage genotypes (Brassica oleracea convar. capitata (L.) Alef.) with improved agronomic traits is attainable using modern biotechnological approaches. However, capitata cabbage is relatively recalcitrant to de novo shoot organogenesis from callus tissue, especially with loss of somatic cell totipotency during genetic transformation. An effective and rapid protocol for in vitro indirect shoot organogenesis from hypocotyl and cotyledon explants derived from 6-day-old aseptic donor seedlings of Russian cabbage genotypes (the DH line as well as cvs. Podarok and Parus) has been developed. In order to obtain standardized donor explants, aseptic cabbage seeds were germinated under dim light conditions (30–40 µmol m⁻² s⁻¹) with a 16 h light/8 h dark photoperiod. Multiple indirect shoot organogenesis (1.47–4.93 shoots per explant) from both cotyledonary leaves and hypocotyl segments with a frequency of 55.2–89.1% was achieved through 45 days of culture on the 0.7% agar-solidified (w/v) Murashige and Skoog (MS) basal medium containing 2 mg/L 6-benzylaminopurine (6-BAP), 0.02 mg/L 1-naphthalene acetic acid (NAA), and 5 mg/L AgNO₃. The regenerants were successfully rooted on an MS basal medium (69.2%) without plant growth regulators (PGRs), as well as supplemented with 0.5 mg/L NAA (86.8%). Subsequently, in vitro rooted cabbage plantlets were adapted to soil conditions with an efficiency of 85%. This rapid protocol, allowing for the performance of a full cycle from in vitro seed germination to growing adapted plantlets under ex vitro conditions over 95 days, can be successfully applied to induce an indirect shoot formation in various cabbage genotypes, and it is recommended to produce transgenic plants with improved quality traits and productivity.

LTR retrotransposons are widespread genomic elements that significantly impact genome structure and function. In Arabidopsis thaliana, the EVD LTR retrotransposon encodes a GAG protein essential for retrotransposon particle assembly. Here, we present a comprehensive analysis of the structural features, intracellular localization, and transcriptomic effects of the EVD GAG (evdGAG) protein. Using AlphaFold3, we identified canonical capsid (CA-NTD and CA-CTD) and nucleocapsid (NC) domains, with predicted disordered regions likely facilitating oligomerization. Transient expression of GFP-tagged evdGAG in protoplasts of A. thaliana and distant plant species (Nicotiana benthamiana and Helianthus annuus) revealed the formation of multiple large cytoplasmic aggregates resembling retrosomes, often localized near the nucleus. Stable overexpression of evdGAG in wild-type and ddm1 mutant backgrounds induced significant transcriptomic changes, including up-regulation of stress response and defense-related genes and downregulation of photosynthesis and chloroplast-associated pathways. Importantly, genes linked to stress granule formation were also up-regulated, suggesting a role for evdGAG in modulating cellular stress responses. Our findings provide novel insights into the cellular and molecular properties of plant retrotransposon GAG proteins and their influence on host gene expression.

The antimicrobial activity of the alpha-HAIRPININ ANTIMICROBIAL PEPTIDE X (SmAMP-X gene, GenBank acc. No. HG423454.1) from Stellaria media plant has been shown in vitro. Here, we isolated the SmAMP-X gene promoter and found two genomic sequences for the promoter (designated pro-SmAMP-X and pro-SmAMP-X-Ψ2) with 83% identity in their core and proximal regions. We found that the abilities of these promoters to express the uidA reporter and the nptII selectable marker differ according to the structural organization of T-DNA in the binary vector used for plant transformation. Analysis of Agrobacterium-infiltrated Nicotiana benthamiana leaves, transgenic Arabidopsis thaliana lines, and transgenic Solanum tuberosum plants revealed that both promoters in the pCambia1381Z and pCambia2301 binary vectors generate 42–100% of the ß-glucuronidase (GUS) activity generated by the CaMV35S promoter. According to 5’-RACE (rapid amplification of cDNA ends) analysis, both plant promoters are influenced by the CaMV35S enhancer used to express selectable markers in the T-DNA region of pCambia1381Z and pCambia2301. The exclusion of CaMV35S enhancer from the T-DNA region significantly reduces the efficiency of pro-SmAMP-X-Ψ2 promoter for GUS production. Both promoters in the pCambia2300 vector without CaMV35S enhancer in the T-DNA region weakly express the nptII selectable marker in different tissues of transgenic N. tabacum plants and enable selection of transgenic cells in media with a high concentration of kanamycin. Overall, promoter sequences must be functionally validated in binary vectors lacking CaMV35S enhancer.

Transposable element insertions (TEIs) are an important source of genomic innovation by contributing to plant adaptation, speciation, and the production of new varieties. The often large, complex plant genomes make identifying TEIs from short reads difficult and expensive. Moreover, rare somatic insertions that reflect mobilome dynamics are difficult to track using short reads. To address these challenges, we combined Cas9‐targeted Nanopore sequencing (CANS) with the novel pipeline NanoCasTE to trace both genetically inherited and somatic TEIs in plants. We performed CANS of the EVADÉ (EVD) retrotransposon in wild‐type Arabidopsis thaliana and rapidly obtained up to 40× sequence coverage. Analysis of hemizygous T‐DNA insertion sites and genetically inherited insertions of the EVD transposon in the ddm1 (decrease in DNA methylation 1) genome uncovered the crucial role of DNA methylation in shaping EVD insertion preference. We also investigated somatic transposition events of the ONSEN transposon family, finding that genes that are downregulated during heat stress are preferentially targeted by ONSENs. Finally, we detected hypomethylation of novel somatic insertions for two ONSENs. CANS and NanoCasTE are effective tools for detecting TEIs and exploring mobilome organization in plants in response to stress and in different genetic backgrounds, as well as screening T‐DNA insertion mutants and transgenic plants.

Meiotic crossing over is the main mechanism for constructing a new allelic composition of individual chromosomes and is necessary for the proper distribution of homologous chromosomes between gametes. The parameters of meiotic crossing over that have developed in the course of evolution are determined by natural selection and do not fully suit the tasks of selective breeding research. This review summarizes the results of experimental studies aimed at increasing the frequency of crossovers and redistributing their positions along chromosomes using genetic manipulations at different stages of meiotic recombination. The consequences of inactivation and/or overexpression of the SPO11 genes, the products of which generate meiotic double-strand breaks in DNA, for the redistribution of crossover positions in the genome of various organisms are discussed. The results of studies concerning the effect of inactivation or overexpression of genes encoding RecA-like recombinases on meiotic crossing over, including those in cultivated tomato (Solanum lycopersicum L.) and its interspecific hybrids, are summarized. The consequences of inactivation of key genes of the mismatch repair system are discussed. Their suppression made it possible to significantly increase the frequency of meiotic recombination between homeologues in the interspecific hybrid yeast Saccharomyces cerevisiae × S. paradoxus and between homologues in arabidopsis plants (Arabidopsis thaliana L.). Also discussed are attempts to extrapolate these results to other plant species, in which a decrease in reproductive properties and microsatellite instability in the genome have been noted. The most significant results on the meiotic recombination frequency increase upon inactivation of the FANCM, TOP3α, RECQ4, FIGL1 crossover repressor genes and upon overexpression of the HEI10 crossover enhancer gene are separately described. In some experiments, the increase of meiotic recombination frequency by almost an order of magnitude and partial redistribution of the crossover positions along chromosomes were achieved in arabidopsis while fully preserving fecundity. Similar results have been obtained for some crops.

Long-read data is a great tool to discover new active transposable elements (TEs). However, no ready-to-use tools were available to gather this information from low coverage ONT datasets. Here, we developed a novel pipeline, nanotei, that allows detection of TE-contained structural variants, including individual TE transpositions. We exploited this pipeline to identify TE insertion in the Arabidopsis thaliana genome. Using nanotei, we identified tens of TE copies, including ones for the well-characterized ONSEN retrotransposon family that were hidden in genome assembly gaps. The results demonstrate that some TEs are inaccessible for analysis with the current A. thaliana (TAIR10.1) genome assembly. We further explored the mobilome of the ddm1 mutant with elevated TE activity. Nanotei captured all TEs previously known to be active in ddm1 and also identified transposition of non-autonomous TEs. Of them, one non-autonomous TE derived from (AT5TE33540) belongs to TR-GAG retrotransposons with a single open reading frame (ORF) encoding the GAG protein. These results provide the first direct evidence that TR-GAGs and other non-autonomous LTR retrotransposons can transpose in the plant genome, albeit in the absence of most of the encoded proteins. In summary, nanotei is a useful tool to detect active TEs and their insertions in plant genomes using low-coverage data from Nanopore genome sequencing.

The production of mesophilic protoplasts of potato (Solanum tuberosum L.) for transient gene expression is a required technological stage in the testing of the efficiency of the new genetic constructs, including CRISPR/Cas genome editing. In this study, the leaves of potato plants of nine Russian cultivars were used to isolate protoplasts. These plants were cultivated in vitro for 6–7 weeks in vessels with foil caps to prevent gas exchange with the environment. We demonstrated for the first time that 2.4 × 10⁶ to 4.6 × 10⁶ viable protoplasts can be obtained from 1 g of aseptic plant leaves depending on the used potato cultivar. We found that the level of protoplast transfection with the pHBT-sGFP-NosT genetic construct ranged from 10 to 49% depending on the cultivar, which is sufficient for a successful subsequent analysis of the efficiency of genetic constructs and editing of the potato genome.

In plant breeding, the ability to manipulate meiotic recombination aids in the efficient construction of new allelic compositions of chromosomes and facilitates gene transfer from wild relatives of crop plants. The DNA mismatch repair system antagonizes meiotic recombination. In this research, a trial was conducted to evaluate transgenic tomato plants carrying an RNA interference (RNAi) construct designed to inhibit the expression of the mismatch repair MSH2 gene. To drive the RNAi construct, we used either a pro-SmAMP2 promoter from Stellaria media ANTIMICROBIAL PEPTIDE2 or a Cauliflower mosaic virus 35S promoter (CaMV35S). The results of real-time PCR showed that, with a 16 h light/8 h dark photoperiod, MSH2-RNAi tomato transgenic plants exhibited MSH2 gene transcript contents ranging from 0% to 3% in the leaves, relative to untransformed controls. However, with this lighting mode, the MSH2-RNAi transgenic plants grew slowly, flowered poorly, and did not form seed sets. During cultivation with a 12 h light/12 h dark photoperiod, MSH2-RNAi transgenic plants exhibited MSH2 gene transcript contents ranging from 3% to 42%, relative to untransformed controls. Under these conditions, F₁ hybrid seed sets formed for most of the MSH2-RNAi transgenic plants with the RNAi construct driven by the CaMV35S promoter, and for one transformant with the RNAi construct driven by the pro-SmAMP2 promoter. Under conditions of a 12 h light/12 h dark photoperiod, most of the F₁ transgenic hybrids showed MSH2 gene transcript contents ranging from 3% to 34% and formed F₂ offspring sets, which made it possible to assess the meiotic recombination frequency. We showed that the effective inhibition of MSH2 in MSH2-RNAi tomato transgenic plants is not associated with an increase in meiotic recombination compared to the control, but it stimulates the sterility of plants. It was established that the expression of the MSH2 gene in tomato plants is about 50 times higher with a 12 h light/12 h dark than with a 16 h light/8 h dark photoperiod. It is discussed that, in Solanum lycopersicum tomato plants, which are not sensitive to the day length for flowering, changing the lighting time may be a means of controlling the meiotic recombination frequency within certain limits.

LTR retrotransposons (RTEs) play a crucial role in plant genome evolution and adaptation. Although RTEs are generally silenced in somatic plant tissues under non-stressed conditions, some expressed RTEs (exRTEs) escape genome defense mechanisms. As our understanding of exRTE organization in plants is rudimentary, we systematically surveyed the genomic and transcriptomic organization and mobilome (transposition) activity of sunflower (Helianthus annuus L.) exRTEs. We identified 44 transcribed RTEs in the sunflower genome and demonstrated their distinct genomic features: more recent insertion time, longer open reading frame (ORF) length, and smaller distance to neighboring genes. We showed that GAG-encoding ORFs are present at significantly higher frequencies in exRTEs, compared with non-expressed RTEs. Most exRTEs exhibit variation in copy number among sunflower cultivars and one exRTE Gagarin produces extrachromosomal circular DNA in seedling, demonstrating recent and ongoing transposition activity. Nanopore direct RNA sequencing of full-length RTE RNA revealed complex patterns of alternative splicing in RTE RNAs, resulting in isoforms that carry ORFs for distinct RTE proteins. Together, our study demonstrates that tens of expressed sunflower RTEs with specific genomic organization shape the hidden layer of the transcriptome, pointing to the evolution of specific strategies that circumvent existing genome defense mechanisms.