In this paper, a new species of the genus Rosa from China, Rosa tomurensis L. Luo, C. Yu & Q. X. Zhang, is described and illustrated. In the past, R. tomurensis was considered as a variety of Rosa laxa. After years of field investigation, introduction and cultivation, comparison and measurement of plant specimens, our research team found that R. tomurensis has stable characters, and its morphological characteristics, sporopollen, chromosome karyotype and genome are obviously different from R. laxa. Therefore, it is confirmed that R. tomurensis is an independent species in Rosa.
Rose is one of the most important ornamental and economic plants in the world. Modern rose cultivars are primarily tetraploid, and during meiosis, they may exhibit double reduction or preferential chromosome pairing. Therefore, the construction of a high density genetic map of tetraploid rose is both challenging and instructive. In this study, a tetraploid rose population was used to conduct a genetic analysis using genome sequencing. A total of 17 382 single nucleotide polymorphism (SNP) markers were selected from 2 308 042 detected SNPs. Combined with 440 previously developed simple sequence repeats (SSR) and amplified fragment length polymorphism (AFLP) markers, a marker dosage of 6 885 high quality markers was successfully assigned by GATK software in the tetraploid model. These markers were used in the construction of a high density genetic map, containing the expected seven linkage groups with 6 842 markers, a total map length of 1 158.9 cM, and an average inter-marker distance of 0.18 cM. Quantitative trait locus (QTL) analysis was subsequently performed to characterize the genetic architecture of petal number and flower diameter. One major QTL (qpnum-3-1) was detected for petal number in three consecutive years, which explained 20.18–22.11% of the variation in petal number. Four QTLs were detected for flower diameter; the main locus, qfdia-2-2, was identified in two consecutive years. Our results will benefit the molecular marker-assisted breeding of modern rose cultivars. In addition, this study provides a guide for the genetic and QTL analysis of autotetraploid plants using sequencing-based genotyping methods.
As an alternative for economic biodiesel production, the microbial production of extracellular fatty acid from renewable resources is receiving more concerns recently, since the separation of fatty acid from microorganism cells is normally involved in a series of energy-intensive steps. Many attempts have been made to construct fatty acid producing strains by targeting genes in the fatty acid biosynthetic pathway, while few studies focused on the cultivation process and the mass transfer kinetics.In this study, both strain improvements and cultivation process strategies were applied to increase extracellular fatty acid production by engineered Escherichia coli. Our results showed overexpressing 'TesA and the deletion of fadL in E. coli BL21 (DE3) improved extracellular fatty acid production, while deletion of fadD didn't strengthen the extracellular fatty acid production for an undetermined mechanism. Moreover, the cultivation process controls contributed greatly to extracellular fatty acid production with respect to titer, cell growth and productivity by adjusting the temperature, adding ampicillin and employing on-line extraction. Under optimal conditions, the E. coli strain (pACY-'tesA-ΔfadL) produced 4.8 g L⁻¹ extracellular fatty acid, with the specific productivity of 0.02 g h⁻¹ g⁻¹ dry cell mass, and the yield of 4.4% on glucose, while the ratios of cell-associated fatty acid versus extracellular fatty acid were kept below 0.5 after 15 h of cultivation. The fatty acids included C12:1, C12:0, C14:1, C14:0, C16:1, C16:0, C18:1, C18:0. The composition was dominated by C14 and C16 saturated and unsaturated fatty acids. Using the strain pACY-'tesA, similar results appeared under the same culture conditions and the titer was also much higher than that ever reported previously, which suggested that the supposedly superior strain did not necessarily perform best for the efficient production of desired product. The strain pACY-'tesA could also be chosen as the original strain for the next genetic manipulations.The general strategy of metabolic engineering for the extracellular fatty acid production should be the cyclic optimization between cultivation performance and strain improvements. On the basis of our cultivation process optimization, strain improvements should be further carried out for the effective and cost-effective production process.
Rose hips are rich in various nutrients and have long been used for food and medicinal purposes. Owing to the high phenolic content, rose hips can be used as natural antioxidants. In this study, ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to conduct a widely targeted metabolomics analysis on the polyphenolic components of Rosa xanthina f. spontanea in three ripening stages: unripe, half-ripe and fully ripe fruit. A total of 531 polyphenol metabolites were detected, including 220 phenolic acids, 219 flavonoids, 50 tannins and 42 lignans and coumarins. There were 160 differential metabolites between unripe and half-ripe rose hips (61 downregulated and 99 upregulated) and 157 differential metabolites between half-ripe and fully ripe rose hips (107 downregulated and 50 upregulated). The results of our study not only greatly enrich the chemical composition database of rose hips but also provide metabolomics information on the changes in polyphenolic metabolism during fruit development for the first time, which will help select the optimal harvest time of rose hips to achieve better quality.
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