Quercetin alleviates seed germination and growth inhibition in Apocynum venetum and Apocynum pictum under mannitol-induced osmotic stress.

Quercetin is one of the main flavonoids in the human diet and mainly found in different plant tissues, including seeds, flowers, leaves, stems, and roots. However, its biological function in plant tissues, especially in seeds, is unknown. In this study, the seed germination and subsequent seedling growth of Apocynum pictum and A. venetum under osmotic stress (400 mmol L-1 mannitol) supplemented with 5 µmol L-1 quercetin were evaluated after 7, 14, and 21 days of germination. Results showed that quercetin improved the germination percentage and seed vigor, as indicated by the higher germination energy, shoot length, root length, dry weight, fresh weight, and chlorophyll content in A. pictum and A. venetum seedlings under the mannitol compared with those under the mannitol alone. Quercetin decreased H2O2 and O2- production and cell membrane damage, and mostly increased the gene expression of superoxide dismutase, peroxidase, catalase, chalcone synthase and flavonol synthase in A. pictum and A. venetum seedlings under the mannitol compared with those under the mannitol alone. In addition, the germination energy of A. pictum was 21.57% higher than that of A. venetum, and the gene expression of key enzymes in quercetin biosynthesis in A. pictum was mostly higher than that in A. venetum after 1 and 7 days of germination. These results indicated that quercetin was an effective anti-osmotic agent that alleviated the adverse effect of mannitol-induced osmotic stress on seed germination and seed vigor, and A. pictum seeds were more osmotic resistant than A. venetum seeds.

Dataset of full-length transcriptome assembly and annotation of apocynum venetum using pacbio sequel II.

Apocynum venetum, which belongs to Apocynaceae, is widely distributed throughout salt-barren zones, desert steppes, and alluvial flats of the Mediterranean area and Northwestern China. Apocynum venetum has long been used in traditional Chinese medicine because of its anti-inflammation, anti-oxidative, anti-hypertensive, anti-cancer, and bactericidal effects. However, the absence of genetic information on Apocynum venetum is an obstacle to understanding its stress resistance or medicinal function. This work was aimed at generating a full-length transcriptome of Apocynum venetum using Pacific Bioscience (PacBio) Single Molecule Real-Time (SMRT) sequencing technology. A total of 18,524 unigenes were obtained, and 18,136 unigenes were successfully annotated. The raw data were uploaded to SRA database, and the BioProject ID is PRJNA650225. The above data will provide the basis for further exploration and understanding of the molecular mechanism in stress resistance or medicinal function of Apocynum venetum.

[Phyllosphere bacterial community structure of Osmanthus fragrans and Nerium indicum in different habitats.] / ä¸åŒç”Ÿå¢ƒä¸­æ¡‚èŠ±å’Œå¤¹ç«¹æ¡ƒå¶é™ ç»†èŒçš„ç¾¤è½ç»“æž„.

The diversity of phyllosphere bacteria is one of the hotspots in the research area of plant-microbial relationship. There are still a lot of controversies in the main factors influencing community structure of phyllosphere bacteria. In this study, the phyllosphere bacterial community structure of Osmanthus fragrans and Nerium indicum grown in three habitats was investigated based on high-throughput sequencing and the main driving factors were examined. The results showed that there was no significant difference in phyllosphere bacterial diversity between the two plant species grown in three habitats. For phyllosphere bacterial community of two plant species from three habitats, the dominant phyla were Actinobacteria, Bacteroidetes, Chlamydiae, Cyanobacteria, Firmicutes and Proteobacteria, and the dominant genera included Methylobacterium, Sphingomonas, Hymenobacter, Polaromonas and Spirosoma. The structure of phyllosphere bacterial community was influenced by habitats, host species identity and species-habitat interaction, among which habitat showed the strongest effect.

Distribution and expression characteristics of triterpenoids and OSC genes in white birch (Betula platyphylla suk.).

Betulin and oleanolic acids (pentacyclic triterpenoid secondary metabolites) have broad pharmacological activities and can be potentially used for the development of anti-cancer and anti-AIDS drugs. In this study, we detected the accumulation and the distribution characteristics of betulin and oleanolic acid in various organs of white birch at different ages. We also determined the expression of 4 OSC genes (LUS, ß-AS, CAS1 and CAS2) involved in the triterpenoid synthesis pathways by real time RT-PCR. The result showed that the 1-year old birch can synthesize betulin and oleanolic acid. In addition, betulin and oleanolic acids were mainly distributed in the bark, while the content in the root skin and leaf was very low. The content of betulin and oleanolic acid in birch varied in different seasons. The content of betulin and oleanolic acid and their corresponding LUS and ß-AS gene expression were very low in 1-year old birch. With increasing age of birch, betulin content was increased, while oleanolic acid was decreased. Similar changes were also observed for their corresponding synthesis genes LUS and ß-AS. In the leaf of 1-year old plant, the highest expression of CAS1 and CAS2 occurred at end of September, while expression of LUS and the ß-AS was low from June to October. In the stem skin,high expression of ß-AS and the LUS genes occurred from the end of July to September. In the root, high expression of the ß-AS gene was observed at the end of October. These results indicated that triterpenoid gene expression was similar to the triterpene accumulation. Expression of LUS gene and ß-AS gene in birch with different ages were corresponding to the betulinic and oleanolic acid accumulation. Expression of CAS1 and CAS2 genes were elevated with increasing age of birch. This study provides molecular mechanisms of triterpenes synthesis in birch plants.

[Chloroplast genetic engineering: a new approach in plant biotechnology].

Chloroplast genetic engineering, offers several advantages over nuclear transformation, including high level of gene expression, increased biosafety, remedying some limitations associated with nuclear genetic transformation, such as gene silencing and the stability of transformed genes. It is now regarded as an attractive new transgenic technique and further development of biotechnology in agriculture. In this article we reviewed the characteristics, applications of chloroplast genetic engineering and its promising prospects were discussed.

Progress on molecular mechanism of T-DNA transport and integration.

Agrobacterium-mediated transformation is probably the most widely used method to introduce genes into plants. Great progress has been made in recent years in studies on the mechanism of Agrobacterium-mediated transformation. Agrobacterium genetically transforms plants by transferring a portion of the resident Ti-plasmid, the T-DNA, to the plant. VirD2 and VirE2 accompany the T-DNA into the plant cell. Both proteins may aid in T-DNA transfer, nuclear targeting and integration into the plant genome. In recent years, some Arabidopsis rat (resistant to transformation) mutants are deficient in T-DNA integration according to some studies. These results showed that plant genes participate in the T-DNA transport and integration process. This paper discusses our current knowledge about the functions of virulence protein, namely VirD2 and VirE2, and plant genes in several aspect of Agrobacterium transformation. The paper discusses two different classes of integration patterns in detail: one is T-DNA right border being linked to genomic sequences by the VirD2 protein, the other is T-DNA integration via SDSA (synthesis-dependent strand-annealing). According to the latest studies we elaborated the T-DNA integration model based on genomic DSB (double-strand breaks) and proposed a new opinion about the mechanism of T-DNA integration.