Recent advances in development of marker-free transgenic plants: Regulation and biosafety concern

During the efficient genetic transformation of plants with the gene of interest, some selectable marker genes are also used in order to identify the transgenic plant cells or tissues. Usually, antibiotic- or herbicide-selective agents and their corresponding resistance genes are used to introduce economically valuable genes into crop plants. From the biosafety authority and consumer viewpoints, the presence of selectable marker genes in released transgenic crops may be transferred to weeds or pathogenic microorganisms in the gastrointestinal tract or soil, making them resistant to treatment with herbicides or antibiotics, respectively. Sexual crossing also raises the problem of transgene expression because redundancy of transgenes in the genome may trigger homology-dependent gene silencing. The future potential of transgenic technologies for crop improvement depends greatly on our abilities to engineer stable expression of multiple transgenic traits in a predictable fashion and to prevent the transfer of undesirable transgenic material to non-transgenic crops and related species. Therefore, it is now essential to develop an efficient marker-free transgenic system. These considerations underline the development of various approaches designed to facilitate timely elimination of transgenes when their function is no longer needed. Due to the limiting number of available selectable marker genes, in future the stacking of transgenes will be increasingly desirable. The production of marker-free transgenic plants is now a critical requisite for their commercial deployment and also for engineering multiple and complex trait. Here we describe the current technologies to eliminate the selectable marker genes (SMG) in order to develop marker-free transgenic plants and also discuss the regulation and biosafety concern of genetically modified (GM) crops.     

珍珠菜属系统发育关系的初步研究

本文运用形态学性状对珍珠菜属（Lysimachia)进行系统发育分析。内类群包括珍珠菜属29个代表种以及珍珠菜族其它单种、寡种属;仙客来属（Cylclamen)被选作外类群。最简约性分析表明,珍珠菜属并不构成－自然分类群;在其严格一致化树的二岐分支中,异花珍珠菜（L.crispidens)单独构成一支,其它所有内类群构成一支。香草亚属（subgen.Idiophyton)、木黄连花亚属（subgne.Lysimachiopsis)以及珍珠菜亚属（subgen.palladia)均表现为单系群,而黄连花亚属（subgen.Lysimachia)则为一异形的并系群。球尾花亚属（subgen.Naumburgia)仍“内藏”于珍珠菜属的主体之中。而喉鳞花亚属（subgen.Seleucia)则偏离出来而与七瓣莲属（Trien talis)构成姐妹群。如何准确地界定珍珠菜属和进行属下分类群的划分,还需进一步研究。     

Fast evolutionary genetic differentiation during experimental colonizations

Founder effects during colonization of a novel environment are expected to change the genetic composition of populations, leading to differentiation between the colonizer population and its source population. Another expected outcome is differentiation among populations derived from repeated independent colonizations starting from the same source. We have previously detected significant founder effects affecting rate of laboratory adaptation among Drosophila subobscura laboratory populations derived from the wild. We also showed that during the first generations in the laboratory, considerable genetic differentiation occurs between foundations. The present study deepens that analysis, taking into account the natural sampling hierarchy of six foundations, derived from different locations, different years and from two samples in one of the years. We show that striking stochastic effects occur in the first two generations of laboratory culture, effects that produce immediate differentiation between foundations, independent of the source of origin and despite similarity among all founders. This divergence is probably due to powerful genetic sampling effects during the first few generations of culture in the novel laboratory environment, as a result of a significant drop in N _e. Changes in demography as well as high variance in reproductive success in the novel environment may contribute to the low values of N _e. This study shows that estimates of genetic differentiation between natural populations may be accurate when based on the initial samples collected in the wild, though considerable genetic differentiation may occur in the very first generations of evolution in a new, confined environment. Rapid and significant evolutionary changes can thus occur during the early generations of a founding event, both in the wild and under domestication, effects of interest for both scientific and conservation purposes.     

Organization of fusicoccin receptor in higher plant plasma membrane: relationship between affinity and molecular mass

Higher plant plasma membranes carry receptors of different affinity for the phytotoxin fusicoccin. Reception of fusicoccin involves proteins belonging to the highly conserved 14-3-3 family, but the complete structure of the fusicoccin receptor (FCR) is unknown. Using radiation inactivation analysis, we estimated the molecular masses of low-affinity and high-affinity FCR at 63 +/- 7 and 130 +/- 15 kD, respectively. The dose dependences of receptor inactivation indicate that microsomal specimens contain "silent" FCRs of 420 +/- 90 kD in amounts commensurate with that of the active FCRs. Both low- and high-affinity FCRs are inactivated by hydrolytic enzymes from the outer surface of the plasma membrane, and impairment of protoplast integrity causes an irreversible transition of the low-affinity binding site into the high-affinity one. A scheme is proposed for the organization of different types of FCR in the plasma membrane, implying that the membrane affinity for fusicoccin reflects the interaction between proteins in the FCR complex.     

Biometric variations and oxidative stress responses in juvenile Clarias gariepinus exposed to Termex®

The current study investigated the effects of termite insecticide, Termex® (imidacloprid 35.50% SC), on biometric variations and oxidative stress biomarkers in Clarias gariepinus. Fish were exposed to 4.00 and 6.00 µg l^–1 sublethal Termex® concentrations in 2017. The gill and liver tissues were sampled on days 7, 14, 21 and 28 and the results indicated that hepatosomatic index (HSI) decreased significantly when compared with the control on days 14, 21 and 28. The condition factor (CF) and viscera-somatic index (VSI) also decreased during the study period. The decrease was greater at 6.00 µg l^–1 Termex® concentration on days 21 and 28 for CF and days 14 to 28 for VSI, respectively. The lipid peroxidation (LPO) in both tissues was highest in the 6.00 µg l^?1 Termex® and increased with the duration. There was significant decrease (p < 0.05) in superoxide dismutase and glutathione peroxidase values, but significant increase in catalase activity in both tissues. The values of glutathione reductase in both tissues were comparable to the control, except on days 21 and 28 in the liver. There was negative correlation between the LPO in tissues and the HSI, CF and VSI values. The use of Termex® in the environment should be monitored to safeguard the health of aquatic organisms.     

几种念珠菌DNA总含量的流式细胞分析

应用流式细胞术(FCM)对处于稳定生长阶段的念珠菌属(Candida)的7种8株念珠菌进行了DNA总含量的流式细胞(FCM)分析。这8株念珠菌是:白念珠菌(C.albicans)2株,热带念珠菌(C.tropicalis),克柔念珠菌(C.krusei),近平滑念珠菌(C.parapsiolosis),乳酒念珠菌(C.kefyr),白念珠菌星形变种(C.stellatoidea),即血清B型白念珠菌,季也蒙念珠菌(C.guilliermondii)各一株。应用EB一步插入法染色,用鸡红细胞(CRBC)作为内参标准进行DNA总含量测定。分析结果表明:稳定生长阶段的组方图上,大多数念珠菌细胞处于DNA合成周期的G_0/G_1期;DNA总含量有明显的种间和种内差异。     

环境对沼泽红假单胞菌基因型的影响

<正>紫色光合细菌是不产氧光合细菌的一个重要分支,包括紫色非硫细菌和紫色硫细菌。其中紫色非硫细菌具有极其丰富的代谢模式,可进行光能异养、光能自养和化能异养生长,其代谢的多样性使得它们广泛存活于不同的生态系统中,如土壤、湖泊、海洋及底泥等[1-2]。沼泽红假单胞菌(Rhodopseudomonas palustris)是紫