Low impact of polyploidization on the transcriptome of synthetic allohexaploid wheat

In vitro synthetic polyploidization and enhancement of anticancer compounds in Catharanthus Roseus (L.) G. Don important cultivars

Catharanthus roseus (L.) G. Don is a plant belonging to the Apocynaceae family, which is native to Madagascar. The important alkaloids isolated from C. roseus are vinblastine and vincristine, both of which are important early indole-based anticancer drugs. Induction of polyploidy using mutagenic agents serves as an efficient method to improve the genetic potential of cells to synthesize secondary metabolites in medicinal plants. The variety of traits that occur through polyploidy induction, depends on the plant's species and genotypes. In this study, in vitro seedlings of 'Red Really' and 'Polka Dot' cultivars of C. roseus (for the first time) in the cotyledonary stage, were treated with various concentrations of colchicine (0, 0.05, 0.1, 0.2 and 0.5%) at three exposure time (24, 48 and 72 h). To distinguish the ploidy level of seedlings, morphological changes as well as, microscopic examinations, flow cytometry and chromosome counting were performed. In our experiment, the concentration and exposure time of colchicine and their interaction affected the tetraploidy percentage. Karyotype analysis suggested that the number of chromosomes in the diploid species was 2n = 2x = 16 and tetraploid plants contained 2n = 4x = 32. The maximum tetraploidy frequency was observed at 0.2% colchicine for 48 h in 'Red Really' and 0.1% colchicine for 48 h in 'Polka Dot'. The polyploid seedlings produced visible changes in plant height, leaf length and width, plant fresh and dry weight, stem and flower diameter compared to the control. Artificial ploidy manipulation caused significant changes in the chlorophyll and carotenoid content in polyploid seedlings compared to diploids. Also, vincristine, vinblastine, catharanthine and vindoline content increased 82.2, 80.9, 44.3 and 71.2% in Red Really as well as 64.7, 31, 48.2 and 95.3% in Polka Dot, respectively, compared to diploid plants. Increasing the ploidy level as an effective breeding strategy is noticeable for commercially producing these valuable medicinal compounds. The resulting polyploid lines have the potential to be used in breeding programs to develop C. roseus cultivars.

Chromosome-level assembly of basil genome unveils the genetic variation driving Genovese and Thai aroma types

Basil, Ocimum basilicum L., is a widely cultivated aromatic herb, prized for its culinary and medicinal uses, predominantly owing to its unique aroma, primarily determined by eugenol for Genovese cultivars or methyl chavicol for Thai cultivars. To date, a comprehensive basil reference genome has been lacking, with only a fragmented draft available. To fill this gap, we employed PacBio HiFi and Hi-C sequencing to construct a homeolog-phased chromosome-level genome for basil. The tetraploid basil genome was assembled into 26 pseudomolecules and further categorized into subgenomes. High levels of synteny were observed between the two basil subgenomes but comparisons to Salvia rosmarinus show collinearity quickly breaks down in near relatives. We utilized a bi-parental population derived from a Genovese × Thai cross to map quantitative trait loci (QTL) for the aroma chemotype. We discovered a single QTL governing the eugenol/methyl chavicol ratio, which encompassed a genomic region with 95 genes, including 15 genes encoding a shikimate O-hydroxycinnamoyltransferase (HCT/CST) enzyme. Of them, only ObHCT1 exhibited significantly higher expression in the Genovese cultivar and showed a trichome-specific expression. ObHCT1 was functionally confirmed as a genuine HCT enzyme using an in vitro assay. The high-quality, contiguous basil reference genome is now publicly accessible at BasilBase, a valuable resource for the scientific community. Combined with insights into cell-type-specific gene expression, it promises to elucidate specialized metabolite biosynthesis pathways at the cellular level.

The Genomic Shock Hypothesis: Genetic and Epigenetic Alterations of Transposable Elements after Interspecific Hybridization in Plants

Transposable elements (TEs) are major components of plant genomes with the ability to change their position in the genome or to create new copies of themselves in other positions in the genome. These can cause gene disruption and large-scale genomic alterations, including inversions, deletions, and duplications. Host organisms have evolved a set of mechanisms to suppress TE activity and counter the threat that they pose to genome integrity. These includes the epigenetic silencing of TEs mediated by a process of RNA-directed DNA methylation (RdDM). In most cases, the silencing machinery is very efficient for the vast majority of TEs. However, there are specific circumstances in which TEs can evade such silencing mechanisms, for example, a variety of biotic and abiotic stresses or in vitro culture. Hybridization is also proposed as an inductor of TE proliferation. In fact, the discoverer of the transposons, Barbara McClintock, first hypothesized that interspecific hybridization provides a "genomic shock" that inhibits the TE control mechanisms leading to the mobilization of TEs. However, the studies carried out on this topic have yielded diverse results, showing in some cases a total absence of mobilization or being limited to only some TE families. Here, we review the current knowledge about the impact of interspecific hybridization on TEs in plants and the possible implications of changes in the epigenetic mechanisms.

Investigating the dynamic responses of Aegilops tauschii Coss. to salinity, drought, and nitrogen stress: a comprehensive study of competitive growth and biochemical and molecular pathways

Aegilops tauschii (Coss.) is a highly deleterious, rapidly proliferating weed within the wheat, and its DD genome composition exhibits adaptability toward diverse abiotic stresses and demonstrates heightened efficacy in nutrient utilization. Current study investigated different variegated impacts of distinct nitrogen concentrations with varied plant densities, scrutinizing the behavior of Ae. tauschii under various salinity and drought stress levels through multiple physiological, biochemical, and molecular pathways. Different physiological parameters attaining high growth with different plant density and different nitrogen availability levels increased Ae. tauschii dominancy. Conversely, under the duress of salinity and drought, Ae. tauschii showcased an enhanced performance through a comprehensive array of physiological and biochemical parameters, including catalase, peroxidase, malondialdehyde, and proline content. Notably, salinity-associated traits such as sodium, potassium, and the sodium-potassium ratio exhibited significant variations and demonstrated remarkable tolerance capabilities. In the domain of molecular pathways, the HKT and DREB genes have displayed a remarkable upregulation, showcasing a comparatively elevated expression profile in reaction to different levels of salinity and drought-induced stress. Without a doubt, this information will make a substantial contribution to the understanding of the fundamental behavioral tendencies and the efficiency of nutrient utilization in Ae. tauschii. Moreover, it will offer innovative viewpoints for integrated management, thereby enabling the enhancement of strategies for adept control and alleviation.