[Cloning and expression analysis of 8 bHLH transcription factors in Panax quinquefolius].

A total of 8 bHLH transcription factors were cloned from Panax quinquefolius and the response of them to methyl jasmonate(MeJA) was studied.To be specific, based on the preliminary transcriptome screening, 8 bHLH transcription factors were cloned with seedlings which had been cultured for 3 weeks.The content of ginsenosides Rg_1, Re, and Rb_1, and total saponins in the adventitious roots of P.quinquefolius was determined at different time of MeJA treatment by high performance liquid chromatography(HPLC) and spectrophotometry.Real-time quantitative polymerase chain reaction(PCR) was used to detect the relative expression of 8 transcription factors after MeJA treatment.The correlation between the relative expression of the 8 transcription factors and the saponin content after MeJA treatment was checked by Pearson's correlation analysis.The results showed that the PCR products(Pq-bHLH21-Pq-bHLH28) of the 8 bHLH transcription factors were 762-2 013 bp in length.They were submitted to NCBI to obtain the Genbank access numbers.The proteins yielded from Pq-bHLH21-Pq-bHLH28 showed amino acid sequence identity of 24.90%, and each amino acid sequence had the bHLH(Basic Helix-loop-helix) conserved domain and belonged to the bHLH family.The 5 amino acid sequences of Pq-bHLH22 and Pq-bHLH24-Pq-bHLH27 contained the bHLH-MYC N domain, which belonged to the MYC transcription factors.Pq-bHLH21-Pq-bHLH28 responded to MeJA within 48 h of treatment.At 72 h, the expression of Pq-bHLH24 reached 106.53 folds the highest in the treatment group.Pq-bHLH25, Pq-bHLH27, and Pq-bHLH28 showed synergic expression.Pq-bHLH21 may re-gulate the biosynthetic pathway of ginsenoside Rb_1, while Pq-bHLH22, Pq-bHLH25, and Pq-bHLH28 were in significantly positive correlation with the biosynthetic pathway of ginsenoside Re.The result lays a foundation for further verifying the regulation of ginsenoside biosynthesis by bHLH transcription factors.

[Impact of biocontrol agent Bacillus subtilis on bacterial communities in tobacco rhizospheric soil].

The impact of inoculation with the biocontrol agent Bacillus subtilis on bacterial communities and bacterial diversity in rhizospheric soil of Nicotiana tabacum was assessed by constructing a 16S rRNA gene clone library and conducting amplified ribosomal DNA restriction analysis (ARDRA). The bacterial diversity was evaluated by coverage value (C), Shannon index (H), Pielou evenness index (E) and Margalef richness index (R). Phylogenetic analysis revealed that the inoculation significantly affected the composition of bacterial communities in tobacco rhizospheric soil. A total of twelve bacterial groups including Acidobacteria, Proteobacteria (including α-, ß-, δ-, γ-Proteobacteria) , Planctomycetes, Firmicutes, Nitrospirae, Gemmatimonadetes, Actinobacteria, Chloroflexi and Bacteroidetes were detected to be shared by inoculated soil and control soil. The community composition and proportions of different bacteria in the communities showed significant variations between the two samples. The dominant bacteria were Acidobacteria (27.1%) and Proteobacteria (26.5%) in control soil, while in the inoculated soil Proteobacteria (38.0%) and Acidobacteria (29.6%) were dominant. B. subtilis inoculation increased the numbers of γ-Proteobacteria and α-Proteobacteria but reduced the numbers of bacterial groups such as ß-Proteobacteria, Planctomycetes, Firmicutes. Diversity analysis showed that bacterial diversity was rich for both soil samples, and soil bacterial Shannon index and Margalef richness index were promoted after inoculation.