SrUGT76G1,the most well-studied diterpene glycosyltransferase in Stevia rebaudiana,is key to the biosynthesis of economically important steviol glycosides(SGs).However,the molecular regulatory mechanism of SrUGT76G1 h...SrUGT76G1,the most well-studied diterpene glycosyltransferase in Stevia rebaudiana,is key to the biosynthesis of economically important steviol glycosides(SGs).However,the molecular regulatory mechanism of SrUGT76G1 has rarely been explored.In this study,we identified a MYB transcription factor,SrMYB1,using a yeast one-hybrid screening assay.SrMYB1 belongs to the typical R2R3-type MYB protein and is specifically localized in the nucleus with strong transactivation activity.The transcript of SrMYB1 is predominantly accumulated in flowers,but is also present at a lower level in leaves.Yeast one-hybrid and electrophoretic mobility shift assays verified that SrMYB1 binds directly to the MYB binding sites in the F4-3 fragment(+50–(–141))of the SrUGT76G1 promoter.Furthermore,we found that SrMYB1 could significantly repress the expression of SrUGT76G1 in both epidermal cells of tobacco leaves and stevia callus.Taken together,our results demonstrate that SrMYB1 is an essential upstream regulator of SrUGT76G1 and provide novel insight into the regulatory network for the SGs metabolic pathway in S.rebaudiana.展开更多
Energy minimization has been widely used for constructing curve and surface in the fields such as computer-aided geometric design, computer graphics. However, our testing examples show that energy minimization does no...Energy minimization has been widely used for constructing curve and surface in the fields such as computer-aided geometric design, computer graphics. However, our testing examples show that energy minimization does not optimize the shape of the curve sometimes. This paper studies the relationship between minimizing strain energy and curve shapes, the study is carried out by constructing a cubic Hermite curve with satisfactory shape. The cubic Hermite curve interpolates the positions and tangent vectors of two given endpoints. Computer simulation technique has become one of the methods of scientific discovery, the study process is carried out by numerical computation and computer simulation technique. Our result shows that： （1） cubic Hermite curves cannot be constructed by solely minimizing the strain energy; （2） by adoption of a local minimum value of the strain energy, the shapes of cubic Hermite curves could be determined for about 60 percent of all cases, some of which have unsatisfactory shapes, however. Based on strain energy model and analysis, a new model is presented for constructing cubic Hermite curves with satisfactory shapes, which is a modification of strain energy model. The new model uses an explicit formula to compute the magnitudes of the two tangent vectors, and has the properties： （1） it is easy to compute; （2） it makes the cubic Hermite curves have satisfactory shapes while holding the good property of minimizing strain energy for some cases in curve construction. The comparison of the new model with the minimum strain energy model is included.展开更多
Z-Asp-Val-Tyr-NH2,a precursor tripeptide of thymopentin（TP-5）,was successfully synthesized by a combination of chemical and enzyme methods.Firstly,the precursor dipeptide Val-Tyr-NH2 was synthesized by a novel chemi...Z-Asp-Val-Tyr-NH2,a precursor tripeptide of thymopentin（TP-5）,was successfully synthesized by a combination of chemical and enzyme methods.Firstly,the precursor dipeptide Val-Tyr-NH2 was synthesized by a novel chemical method in four steps including the preparation of NCA-Val,the esterification of L-tyrosine and the ammonolysis of L-tyrosine ethyl ester,and the formation of Val-Tyr-NH2 from NCA-Val and L-Tyr-NH2.Secondly,a thermolysin,thermoase PC 10F was used to catalyze the formation of Z-Asp-Val-Tyr-NH2 in an aqueous/organic solvent diphase system with Z-Asp-OH and Val-Ty-NH2 as the substrates under thermodynamic control.The optimum conditions were pH=6.5,40 ℃,thermoase 100 mg,in 2-（N-morpholino） ethanesulfonic acid MES/NaOH（containing 5 mmol/L CaCl2） of n-butanol system（15/85,volume ratio） for 20 h in a maximum yield of 27.02%.展开更多
目的建立麻疹疫苗株Schwarz(MVSW)反向遗传系统。方法将MVSW全长cDNA分为F1~F7共7个片段,在F1片段的5′端插入T7启动子及锤头核酸酶序列(hammerhead ribozyme,HamRz),F7片段的3′端插入T7终止子及丁型肝炎病毒核酶序列(hepatitis D viru...目的建立麻疹疫苗株Schwarz(MVSW)反向遗传系统。方法将MVSW全长cDNA分为F1~F7共7个片段,在F1片段的5′端插入T7启动子及锤头核酸酶序列(hammerhead ribozyme,HamRz),F7片段的3′端插入T7终止子及丁型肝炎病毒核酶序列(hepatitis D virus ribozyme,HdvRz),分别将F1~F7片段克隆至pT7-MCS2载体上,7个重组质粒经酶切按顺序拼接MVSW全长cDNA,获得全长质粒pT7MVSW。同时构建表达MVSW核蛋白(N)、磷蛋白(P)、大蛋白(L)的3个辅助质粒。将全长质粒与3个辅助质粒及表达T7RNA聚合酶的质粒(pT7-T7RNAP及pCDIBP-T7RNAP)共同电转染Vero细胞,拯救获得病毒rMV_(SW)。收获的rMV_(SW)在Vero及CEC细胞中进行传代培养,观察细胞病变、检测病毒滴度并进行病毒测序,同时免疫小鼠检测抗r MVSW中和抗体。结果经酶切鉴定,全长质粒及辅助质粒均构建正确。拯救病毒rMV_(SW)在Vero及CEC细胞培养的病变典型特征类似;P2代病毒rMV_(SW)扩增片段与疫苗株MVSW理论序列一致;rMV_(SW)经Vero细胞连续培养P2~P10代病毒滴度稳定在5.5~6.5 lgCCID_(50)/mL之间;rMV_(SW)及疫苗株MVS191诱导的抗rMV_(SW)抗体滴度接近。结论成功建立了麻疹疫苗株MVSW的反向遗传系统,获得的具有良好遗传稳定性及免疫原性的拯救病毒rMV_(SW)有作为疫苗生产用毒种的潜力。展开更多
基金supported by the National Natural Science Foundation of China(31901597)the Natural Science Foundation of Jiangsu Province,China(BK20201243)。
文摘SrUGT76G1,the most well-studied diterpene glycosyltransferase in Stevia rebaudiana,is key to the biosynthesis of economically important steviol glycosides(SGs).However,the molecular regulatory mechanism of SrUGT76G1 has rarely been explored.In this study,we identified a MYB transcription factor,SrMYB1,using a yeast one-hybrid screening assay.SrMYB1 belongs to the typical R2R3-type MYB protein and is specifically localized in the nucleus with strong transactivation activity.The transcript of SrMYB1 is predominantly accumulated in flowers,but is also present at a lower level in leaves.Yeast one-hybrid and electrophoretic mobility shift assays verified that SrMYB1 binds directly to the MYB binding sites in the F4-3 fragment(+50–(–141))of the SrUGT76G1 promoter.Furthermore,we found that SrMYB1 could significantly repress the expression of SrUGT76G1 in both epidermal cells of tobacco leaves and stevia callus.Taken together,our results demonstrate that SrMYB1 is an essential upstream regulator of SrUGT76G1 and provide novel insight into the regulatory network for the SGs metabolic pathway in S.rebaudiana.
基金Supported by the National Natural Science Foundation of China(61173174,61103150,61373078)the NSFC Joint Fund with Guangdong under Key Project(U1201258)the National Research Foundation for the Doctoral Program of Higher Education of China(20110131130004)
文摘Energy minimization has been widely used for constructing curve and surface in the fields such as computer-aided geometric design, computer graphics. However, our testing examples show that energy minimization does not optimize the shape of the curve sometimes. This paper studies the relationship between minimizing strain energy and curve shapes, the study is carried out by constructing a cubic Hermite curve with satisfactory shape. The cubic Hermite curve interpolates the positions and tangent vectors of two given endpoints. Computer simulation technique has become one of the methods of scientific discovery, the study process is carried out by numerical computation and computer simulation technique. Our result shows that： （1） cubic Hermite curves cannot be constructed by solely minimizing the strain energy; （2） by adoption of a local minimum value of the strain energy, the shapes of cubic Hermite curves could be determined for about 60 percent of all cases, some of which have unsatisfactory shapes, however. Based on strain energy model and analysis, a new model is presented for constructing cubic Hermite curves with satisfactory shapes, which is a modification of strain energy model. The new model uses an explicit formula to compute the magnitudes of the two tangent vectors, and has the properties： （1） it is easy to compute; （2） it makes the cubic Hermite curves have satisfactory shapes while holding the good property of minimizing strain energy for some cases in curve construction. The comparison of the new model with the minimum strain energy model is included.
基金Supported by the National High Technology Research and Development Program of China(No.2008AA10Z321)the Social Development Project of Science and Technology Department of Jilin Province,China(Nos.200805133 and 20090133)
文摘Z-Asp-Val-Tyr-NH2,a precursor tripeptide of thymopentin（TP-5）,was successfully synthesized by a combination of chemical and enzyme methods.Firstly,the precursor dipeptide Val-Tyr-NH2 was synthesized by a novel chemical method in four steps including the preparation of NCA-Val,the esterification of L-tyrosine and the ammonolysis of L-tyrosine ethyl ester,and the formation of Val-Tyr-NH2 from NCA-Val and L-Tyr-NH2.Secondly,a thermolysin,thermoase PC 10F was used to catalyze the formation of Z-Asp-Val-Tyr-NH2 in an aqueous/organic solvent diphase system with Z-Asp-OH and Val-Ty-NH2 as the substrates under thermodynamic control.The optimum conditions were pH=6.5,40 ℃,thermoase 100 mg,in 2-（N-morpholino） ethanesulfonic acid MES/NaOH（containing 5 mmol/L CaCl2） of n-butanol system（15/85,volume ratio） for 20 h in a maximum yield of 27.02%.
