Jiakuan Chen

Effects of VA mycorrhizae and Frankia dual inoculation on growth and nitrogen fixation of Hippophae tibetana

Abstract Through biological inoculation technology, the joint symbiosis of Tibetan seabuckthorn (Hippophae tibetana) in pure culture was identified and the effects of dual inoculation with Frankia and mycorrhizal fungi on the host plants in pot cultures were investigated. The results obtained from the comparative study showed that H. tibetana could form nodules and VA mycorrhiza both in pot and pure cultures. VA mycorrhizae and Frankia can stimulate the growth and the nitrogen fixation ability of host plants, respectively, yet the stimulation of the dual inoculation on the growth and nitrogen fixation ability of the host plants was more significant (p

Global transcriptome analysis profiles metabolic pathways in traditional herb Astragalus membranaceus Bge. var. mongolicus (Bge.) Hsiao

BackgroundAstragalus membranaceus Bge. var. mongolicus (Bge.) Hsiao (A. mongolicus, family Leguminosae) is one of the most important traditional Chinese herbs. Among many secondary metabolites it produces, the effective bioactive constituents include isoflavonoids and triterpene saponins. The genomic resources regarding the biosynthesis of these metabolites in A. mongolicus are limited. Although roots are the primary material harvested for medical use, the biosynthesis of the bioactive compounds and its regulation in A. mongolicus are not well understood. Therefore, a global transcriptome analysis on A. mongolicus tissues was performed to identify the genes essential for the metabolism and to profile their expression patterns in greater details.ResultsRNA-sequencing was performed for three different A. mongolicus tissues: leaf, stem, and root, using the Illumina Hiseq2000 platform. A total of 159.5 million raw sequence reads were generated, and assembled into 186,324 unigenes with an N50 of 1,524bp. Among them, 129,966 unigenes (~69.7%) were annotated using four public databases (Swiss-Prot, TrEMBL, CDD, Pfam), and 90,202, 63,946, and 78,326 unigenes were found to express in leaves, roots, and stems, respectively. A total of 8,025 transcription factors (TFs) were identified, in which the four largest families, bHLH, MYB, C3H, and WRKY, were implicated in regulation of tissue development, metabolisms, stress response, etc. Unigenes associated with secondary metabolism, especially those with isolavonoids and triterpene saponins biosynthesis were characterized and profiled. Most genes involved in the isoflavonoids biosynthesis had the lowest expression in the leaves, and the highest in the stems. For triterpene saponin biosynthesis, we found the genes in MVA and non-MVA pathways were differentially expressed among three examined tissues, indicating the parallel but compartmentally separated biosynthesis pathways of IPP and DMAPP in A. mongolicus. The first committed enzyme in triterpene saponin biosynthesis from A. mongolicus, cycloartenol synthase (AmCAS), which belongs to the oxidosqualene cyclase family, was cloned by us to study the astragalosides biosynthesis. Further co-expression analysis indicated the candidate CYP450s and glycosyltransferases (GTs) in the cascade of triterpene saponins biosynthesis. The presence of the large CYP450 families in A. mongolicus was further compared with those from Medicago truncatula and Arabidopsis thaliana, and the diversity and phylegenetic relationships of the CYP450 families were established.ConclusionA transcriptome study was performed for A. mongolicus tissues to construct and profile their metabolic pathways, especially for the important bioactive molecules. The results revealed a comprehensive profile for metabolic activities among tissues, pointing to the equal importance of leaf, stem, and root in A. mongolicus for the production of bioactive compounds. This work provides valuable resources for bioengineering and in vitro synthesis of the natural compounds for medical research and for potential drug development.

Effect of inoculation with ecto- and arbuscular mycorrhizae and Rhizobium on the growth and nitrogen fixation by black locust, Robinia pseudoacacia

Experiments were made to determine the effect of inoculation withRhizobium, the ectomycorrhizal fungus Hebelomamesophasem and the arbuscular mycorrhizal fungus Glomuscaledonium on the growth and nitrogen fixation of black locust(Robinia pseudoacacia Linn.) seedlings grown invitro and in pot culture. The results showed that both mycorrhizalfungi and Rhizobium stimulated the growth and nitrogenfixing ability of inoculated seedlings. Inoculation with all three microbestogether produced the most beneficial effects on nitrogen fixation, mycorrhizaldevelopment and seedling growth.

Molecular Genetic Variation in Chinese Populations of Three Subspecies of Hippophae rhamnoides

To provide a population-level genetic profile for investigation and conservation of genetic diversity of the sea buckthorn (Hippophae rhamnoidesL.), 300 individuals of fifteen natural populations of sea buckthorn in China were analyzed by using ISSR (inter-simple sequence repeats) markers. On the basis of Shannons index and Neis genetic diversity, the mean genetic diversity detected in the natural populations of Hippophae rhamnoidesssp. yunnanensis, ssp. sinensis, and ssp. gyantsensis was 0.1944, 0.2169, and 0.1372, respectively. The coefficient of gene differentiation (Gst) of seven ssp. yunnanensis populations is 0.2790, and that of seven ssp. sinensis populations is 0.4184. This means that 28% of the total molecular variance of seven ssp. yunnanensis populations existed among populations, and 42% for seven ssp. sinensis populations, suggesting that the subspecies have different genetic structures. No significant correlation between genetic and geographic distances of the populations was found using ISSR markers.

Genetic diversity of sea buckthorn (Hippophae rhamnoides) populations in northeastern and northwestern China as revealed by ISSR markers

As a N2-fixing tree species, sea buckthorn (Hippophae rhamnoides) is well adapted to arid regions and is utilized for multiple purposes in China. Current knowledge of genetic variability of H. rhamnoides is limited in terms of rangewide distributions. Eleven natural populations of sea buckthorn in northeastern and northwestern China were analyzed to detect genetic variation among and within populations, by use of ISSR (inter-simple sequence repeats) markers. Using eight primers, 207 polymorphic loci were observed, ranging in size from 250 to 2500 bp. The coefficient of gene differentiation (Gst = 0.0679) showed that the total molecular variance of 11 populations was mainly existed within populations. The genetic variation within and among the 11 populations was 93.21 and 6.79%, respectively. No significant correlation between genetic and geographic distances of the populations was found using ISSR markers. Our study provides a population-level genetic profile for further investigation and conservation of genetic diversity of sea buckthorn.