高产杀粉蝶菌素的链霉菌鉴定及其拮抗水稻白叶枯菌活性研究

【目的】为保证农业生产可持续性发展,研发和使用环境友好的生物农药受到全社会的高度重视。微生物代谢产物农药是我国目前应用最广的生物农药,也是未来发展绿色农药的一个重要方向。【方法】利用包含水稻白叶枯菌(Xanthomonas oryzae pv. oryzae, Xoo) PXO99A的NA培养基琼脂平板,从水稻根际土壤中筛选能抑制Xoo生长的链霉菌。通过高效液相色谱和质谱分析活性代谢产物的化学结构;采用剪叶法接种Xoo到水稻叶片后,再喷施杀粉蝶菌素溶液(0.1 g/L),2周后测定叶枯症状;采用响应面分析法优化高产杀粉蝶菌素的发酵培养基;采用PacBio SMRT测序平台+Illumina HiSeq X Ten平台开展全基因组测序。平均核苷酸一致性(average nucleotide identity,ANI)用于比较HSW2009与其他链霉菌在全基因组水平的亲缘关系。【结果】分离到一株对Xoo生长有强抑制活性的链霉菌HSW2009,其活性代谢产物为杀粉蝶菌素A1(piericidin A1,简称PIE);喷施PIE可以减轻Xoo在水稻叶片内的侵染;优化HSW2009高产PIE的发...     

Soluble Sema4D cleaved from osteoclast precursors by TACE suppresses osteoblastogenesis

Bone remodelling is mediated by orchestrated communication between osteoclasts and osteoblasts which, in part, is regulated by coupling and anti-coupling factors. Amongst formally known anti-coupling factors, Semaphorin 4D (Sema4D), produced by osteoclasts, plays a key role in downmodulating osteoblastogenesis. Sema4D is produced in both membrane-bound and soluble forms; however, the mechanism responsible for producing sSema4D from osteoclasts is unknown. Sema4D, TACE and MT1-MMP are all expressed on the surface of RANKL-primed osteoclast precursors. However, only Sema4D and TACE were colocalized, not Sema4D and MT1-MMP. When TACE and MT1-MMP were either chemically inhibited or suppressed by siRNA, TACE was found to be more engaged in shedding Sema4D. Anti-TACE-mAb inhibited sSema4D release from osteoclast precursors by ~90%. Supernatant collected from osteoclast precursors (OC-sup) suppressed osteoblastogenesis from MC3T3-E1 cells, as measured by alkaline phosphatase activity, but OC-sup harvested from the osteoclast precursors treated with anti-TACE-mAb restored osteoblastogenesis activity in a manner that compensates for diminished sSema4D. Finally, systemic administration of anti-TACE-mAb downregulated the generation of sSema4D in the mouse model of critical-sized bone defect, whereas local injection of recombinant sSema4D to anti-TACE-mAb-treated defect upregulated local osteoblastogenesis. Therefore, a novel pathway is proposed whereby TACE-mediated shedding of Sema4D expressed on the osteoclast precursors generates functionally active sSema4D to suppress osteoblastogenesis.     

Recombinant and wild-type Pseudomonas aureofaciens strains in soil: survival, respiratory activity and effects on nodulation of whitebean Phaseolus vulgaris L. by Rhizobiutn species

Survival and respiratory activity of a genetically engineered Pseudomonas aureofaciens Ps3732RNL11 were compared to the parental wild-type P. aureofaciens Ps3732RN in loam and sandy loam soils over 17- and 28-day periods. Survival and respiratory activity of P. aureofaciens Ps3732RNL11 was not statistically significantly different from that of P. aureofaciens Ps3732RN. Soil texture had an effect on respiratory activity; carbon dioxide evolution was significantly higher in the sandy loam soil. This effect was observed on days 2, 10 and 18 but not on day 24. The presence of P. aureofaciens Ps3732RNL11 and Ps3732RN did not significantly affect growth of whitebean ( Phaseolus vulgaris L.) in vermiculite, loam, or sandy loam soils. There was no significant difference (95% level) in numbers of nodules produced in the presence of P. aureofaciens Ps3732RNL11 and Ps3732RN as a result of the symbiotic relationship between Rhizobium phaseoli and the whitebean roots in vermiculite. Enumeration of nodules on whitebean roots in loam and sandy loam soils was not conducted due to difficulties in removing intact roots from the soils.     

Comparative transmission of, and varietal reaction to, three isolates of rice tungro virus disease

Comparative transmission by leafhoppers of three tungro isolates obtained from the Philippines, India and Malaysia, and of an infectious clone of the Philippine isolate of rice tungro bacilliform virus (RTBV) by agroinoculation, was conducted on 12 rice cultivars. The symptoms, including height of inoculated plants were recorded and the efficiency of RTBV and rice tungro spherical virus (RTSV) transmission was determined by enzyme-linked immunosorbent assay. In most cases, the reduction of height and leaf symptoms of plants infected with RTBV and/or RTSV by the three isolates were similar in any given cultivar. On cultivar ASD 7 , the Malaysian isolate showed more severe yellow orange leaf discolouration symptoms than the Indian isolate which in turn had more severe leaf discolouration than the Philippine isolate. On the other hand, cultivars ASD 7 and Ptb 18 produced the most severe yellow orange leaf discolouration when agroinoculated with an infectious RTBV clone of the Philippine isolate. There was some variation in the transmission profile of the two tungro viruses among the three isolates. However, there was no one clear set of characteristics by which one could use cultivars to distinguish isolates. The amount of viral DNA in agroinfected plants of cultivars Utri merah, Balimau putih, Utri Rajapan and ARC 11554 was low, while the amount was high in cultivars TN1, ASD7, Ptb 18 and TKM 6. There was high correlation between the amount of viral coat protein by ELISA and viral nucleic acid by DNA hybridisation on 10 agroinoculated rice cultivars; this might indicate that similar proportions of the total RTBV DNA are encapsidated in each cultivar.