No abstract

The M‐superfamily with the typical Cys framework (–CC–C–C–CC–) is one of the seven major superfamilies of conotoxins found in the venom of cone snails. Based on the number of residues in the last Cys loop (between C4 and C5), M‐superfamily conotoxins can be provisionally categorized into four branches (M‐1, M‐2, M‐3, M‐4) [Corpuz GP, Jacobsen RB, Jimenez EC, Watkins M, Walker C, Colledge C, Garrett JE, McDougal O, Li W, Gray WR, et al. (2005) Biochemistry44, 8176–8186]. Here we report the purification of seven M‐superfamily conotoxins from Conus marmoreus (five are novel and two are known as mr3a and mr3b) and one known M‐1 toxin tx3a from Conus textile. In addition, six novel cDNA sequences of M‐superfamily conotoxins have been identified from C. marmoreus, Conus leopardus and Conus quercinus. Most of the above novel conotoxins belong to M‐1 and M‐2 and only one to M‐3. The disulfide analyses of two M‐1 conotoxins, mr3e and tx3a, revealed that they possess a new disulfide bond arrangement (C1–C5, C2–C4, C3–C6) which is different from those of the M‐4 branch (C1–C4, C2–C5, C3–C6) and M‐2 branch (C1–C6, C2–C4, C3–C5). This newly characterized disulfide connectivity was confirmed by comparing the HPLC profiles of native mr3e and its two regioselectively folded isoforms. This is the first report of three different patterns of disulfide connectivity in conotoxins with the same cysteine framework.

Anatomical, histochemical and phytochemical methods were used to investigate the structure, the localization and content changes of total saikosaponin and saikosaponin-a of the roots of Bupleurum chinense DC. at different developmental stages. Results showed that saikosaponin was mainly distributed in pericycle and primary phloem in the young root; but in the mature root, it was mainly distributed in vascular cambium and secondary phloem. During the whole growth period from the pre-blossom, blossom, fruit, and fruit mature periods until the pre-withering period, it was in the fruit mature period that both the total saikosaponin content and the saikosaponin-a content reached the highest level. So the last 20 d of October was considered as the right collecting season for the drug of B. chinense. In addition, the quality of 1-year-old drug was better than that of 2-year-old drug due to its higher saikosaponin content. On the other hand, judging from the external characteristics of the drug, the one with an acerose taproot and more lateral roots was of better quality. The results offered theoretical bases for selecting medicinal material of high quality and determining the most appropriate harvesting stage and part of B. chinense.

Flavonoids with great medicinal value play an important role in plant individual growth and stress resistance. Flavonol synthetase (FLS) is one of the key enzymes to synthesize flavonoids. However, the role of the FLS gene in flavonoid accumulation and tolerance to abiotic stresses, as well as its mechanism has not yet been investigated systematically in plants. The aim of this research is to evaluate the effect of FLS overexpression on the accumulation of active ingredients and stress resistance inEuphorbia kansui Liou. The results showed that when the EkFLS gene was overexpressed in Arabidopsis thaliana, the accumulation of flavonoids was improved. In addition, when the wild-type and EkFLS overexpressed Arabidopsis plants were treated with ABA and MeJA, compared with WT Arabidopsis, EkFLS overexpressed Arabidopsis promoted stomatal aperture to influence photosynthesis of the plants, which in turn can promote stress resistance. Meanwhile, under MeJA, NaCl, and PEG treatment, EkFLS overexpressed in Arabidopsis induced higher accumulation of flavonoids, which significantly enhanced peroxidase (POD) and superoxide dismutase (SOD) activities that can scavenge reactive oxygen species in cells to protect the plant. These results indicated that EkFLS overexpression is strongly correlated to the increase of flavonoid synthesis and therefore the tolerance to abiotic stresses in plants, providing a theoretical basis for further improving the quality of medicinal plants and their resistance to abiotic stresses simultaneously.