De novo transcriptome assembly for the five major organs of Zanthoxylum armatum and the identification of genes involved in terpenoid compound and fatty acid metabolism.

BACKGROUND: Zanthoxylum armatum (Z. armatum) is a highly economically important tree that presents a special numbing taste. However, the underlying regulatory mechanism of the numbing taste remains poorly understood. Thus, the elucidation of the key genes associated with numbing taste biosynthesis pathways is critical for providing genetic information on Z. armatumand the breeding of high-quality germplasms of this species. RESULTS: Here, de novo transcriptome assembly was performed for the five major organs of Z. armatum, including the roots, stems, leaf buds, mature leaves and fruits. A total of 111,318 unigenes were generated with an average length of 1014 bp. Additionally, a large number of SSRs were obtained to improve our understanding of the phylogeny and genetics of Z. armatum. The organ-specific unigenes of the five major samples were screened and annotated via GO and KEGG enrichment analysis. A total of 53 and 34 unigenes that were exclusively upregulated in fruit samples were identified as candidate unigenes for terpenoid biosynthesis or fatty acid biosynthesis, elongation and degradation pathways, respectively. Moreover, 40 days after fertilization (Fr4 stage) could be an important period for the accumulation of terpenoid compounds during the fruit development and maturation of Z. armatum. The Fr4 stage could be a key point at which the first few steps of the fatty acid biosynthesis process are promoted, and the catalysis of subsequent reactions could be significantly induced at 62 days after fertilization (Fr6 stage). CONCLUSIONS: The present study realized de novo transcriptome assembly for the five major organs of Z. armatum. To the best of our knowledge, this study provides the first comprehensive analysis revealing the genes underlying the special numbing taste of Z. armatum. The assembled transcriptome profiles expand the available genetic information on this species and will contribute to gene functional studies, which will aid in the engineering of high-quality cultivars of Z. armatum.

[Study of the recognition between alpinetin and calf thymus DNA].

The recognition between alpinetin and DNA under physiological condition (pH 7.4) was investigated by fluorescence and UV-visible spectrometry. The experiment demonstrated that the fluorescence of alpinetin could be quenched by DNA. A quenching mechanism was proved to be the single static quenching procedure according to the deescalating quenching constants Ksv (3.288 X 10(3) , 2.923 X 10(3) and 2.467 X 10(3) L x mol(-1), respectively) along with the escalating temperatures (25, 32 and 39 degrees C) and the quenching rate constant Kq was greater than the maximum scatter collision quenching rate constant of various quenchers with the biomolecule. From the UV-visible spectra of alpinetin and DNA, the result showed that the UV-visible spectra of alpinetin did not changed in the presence of DNA, i. e. neither the decrease in the maximum absorbance intensity nor the red shift of the maximum absorption wavelength changed. Both the fluorescence intensity and the maximum emission wavelength of ethidium bromide-DNA system remained unchanged in the presence of alpinetin, indicating that there is no direct competition for binding DNA between alpinetin and ethidium bromide. Furthermore, DNA thermal denaturation test indicated that the fluorescence quenching effect of alpinetin with unlinking DNA was stronger than that of alpinetin with natural DNA. It was concluded that there was not intercalation binding mode between alpinetin and DNA. At the same time, fluorescence quenching effect and salt effect on the binding of alpinetin with DNA were investigated. It was shown that the major mode of recognition was groove binding between alpinetin and DNA.

[Studies on the interaction between puerarin and bovine serum albumin].

The interaction of puerarin and bovine serum albumin (BSA) under physiological condition was studied by fluorospectrophotometry. The experiment demonstrated that the quenching mechanism of puerarin a BSA was static quenching process. The quenching constant is 7.29 x 10(12) L x mol(-1) x s(-1), and the binding constant is 5.04 x 10(4) L x mol(-1). According to the Forster nonradiative energy transfer theory, the binding distance between donor (BSA) and acceptor (puerarin) was calculated to be 3.35 nm. The influence of the presence of puerarin on structure of BSA was studied by synochronous fluorescence method, the binding distance between BSA and puerarin was also measured, and the binding mechanism was discussed. In addition, the effect of some ions on the binding constant of puerarin with BSA was also studied.