Genomic stability in Nicotiana plants upon silencing of the mismatch repair gene MSH2

Marcke, Inke Van,Angenon, Geert 한국식물생명공학회 2013 Plant biotechnology reports Vol.7 No.4

The Mismatch Repair (MMR) system is a highly conserved pathway for the maintenance of genomic stability in many organisms. In plants, this is particularly important because of the lack of a reserved germline. Suppression of MMR leads to an accumulation of random mutations in the genome over successive generations, and thus maximizes genetic diversity. MMR deficiency has been shown to be a useful technique in plant breeding, complementary to chemical or physical mutagenesis. We have developed an artificial microRNA (amiRNA) targeting the MSH2 gene, which is generally applicable in Solanaceae. Two amiRNA precursors were inserted in a transformation vector, under the control of the CaMV 35S promoter and the meiosis active AtDMC1 promoter, respectively. Introduction of this amiRNA construct in Nicotiana tabacum and N. plumbaginifolia reduced the MSH2 transcript levels to 20-30 %. Morphological and developmental abnormalities and plants with white sectors on the first pair of leaves or on the cotyledons (referred to as 'chimeric albinos') appeared in the transformed Nicotiana lines at higher frequencies than in the control lines. Also, some plants which show an increased tolerance for the herbicide chlorsulfuron were found. However, the mutant phenotypes were not transmitted to subsequent generations. We conclude that the designed amiRNA was capable of suppressing the MSH2 activity, which caused the occurrence of somatic mutations. Apparently, the silencing of MSH2 was not strong enough in the germline to cause inheritable mutations.

Genomic stability in Nicotiana plants upon silencing of the mismatch repair gene MSH2

Inke Van Marcke,Geert Angenon 한국식물생명공학회 2013 Plant biotechnology reports Vol.7 No.4

The Mismatch Repair (MMR) system is a highly conserved pathway for the maintenance of genomic stability in many organisms. In plants, this is particularly important because of the lack of a reserved germline. Suppression of MMR leads to an accumulation of random mutations in the genome over successive generations, and thus maximizes genetic diversity. MMR deficiency has been shown to be a useful technique in plant breeding, complementary to chemical or physical mutagenesis. We have developed an artificial microRNA (amiRNA) targeting the MSH2 gene, which is generally applicable in Solanaceae. Two amiRNA precursors were inserted in a transformation vector, under the control of the CaMV 35S promoter and the meiosis active AtDMC1 promoter, respectively. Introduction of this amiRNA construct in Nicotiana tabacum and N. plumbaginifolia reduced the MSH2 transcript levels to 20–30 %. Morphological anddevelopmental abnormalities and plants with white sectors on the first pair of leaves or on the cotyledons (referred to as ‘chimeric albinos’) appeared in the transformed Nicotiana lines at higher frequencies than in the control lines. Also, some plants which show an increased tolerance for the herbicide chlorsulfuron were found. However, themutant phenotypes were not transmitted to subsequent generations. We conclude that the designed amiRNA was capable of suppressing the MSH2 activity, which causedthe occurrence of somatic mutations. Apparently, the silencing of MSH2 was not strong enough in the germline to cause inheritable mutations.

Exact Nuclear Data Uncertainty Propagation for Fusion Design

D. Rochman,A. J. Koning,S. C. van der Marck 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

Recently, we have presented an exact method (now called ``Total Monte Carlo'') to propagate uncertainties of fundamental nuclear physics experiments, models and parameters to large and complicated nuclear systems. We now show that such exact uncertainty calculations are directly relevant to the optimal and safe design of fusion systems by applying this methodology to a series of fusion shielding benchmarks, namely those connected to the Oktavian, FNS and LLNL experiments. Uncertainties on neutron and gamma leakage fluxes for shielding benchmarks are obtained. Uncertainties for cross sections, angular distributions, single- and double-differential emission spectra, and gamma-ray production cross sections are considered.

SECURING BUSINESS-TO-BUSINESS RELATIONSHIPS: THE IMPACT OF SWITCHING COSTS

Markus Blut,Heiner Evanschitzky,Christof Backhaus,John Rudd,Michael Marck 글로벌지식마케팅경영학회 2014 Global Marketing Conference Vol.2014 No.7

Although the relationship marketing literature acknowledges the importance of switching costs for increasing customer retention in general, little is known about its relevance in industrial markets. In particular, it is unclear whether switching costs and its dimensions impact relevant behavioral outcomes of buyer-seller relationships in business-to-business (B2B) markets. Against this background, our research intends to make two main contributions: Since we assume differential effects for different types of switching costs, our research first explores the dimensions of switching costs for the B2B domain. Second, it tests the relative impact of the dimensions of switching costs on business customers’ actual purchase behavior. Results suggest that switching costs in B2B settings are a multi-faceted construct, including (i) procedural, (ii) financial, and (iii) relational switching costs. Moreover, we find relational switching costs to be most important for securing B2B buyer-seller relationships since they impact a customer’s (a) share-of-wallet, (b) cross buying behavior, and (c) actual switching behavior. While procedural switching costs only influence share-of-wallet, financial switching costs solely impact customer’s cross-buying behavior across a firm’s product and services categories. These findings contribute to a better understanding about how to secure B2B buyer-seller relationships.

Nuclear Data Uncertainty Propagation for a Sodium Fast Reactor

D. Rochman,A. J. Koning,D. F. Dacruz,S. C. van der Marck 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

Nuclear data uncertainties are propagated from basic theory to a full core model of the Kalimer-600 Korean type Sodium Fast Reactor (SFR) using the TALYS nuclear code system, the "Total Monte Carlo" (TMC) approach and perturbation methods developed at NRG. Nuclear data uncertainties from sodium, iron, and some actinides will be presented together with their impact on parameters such as the sodium void coefficient and k_eff. One of the advantages of the TMC method is that it avoids approximations used in perturbation theories, by applying an exact uncertainty propagation approach. Additionally, full nuclear data uncertainties (cross sections, nu-bar as well as single and double differential data) can be considered.

Nuclear Data Uncertainty Propagation: Total Monte Carlo vs. Covariances

D. Rochman,A. J. Koning,S. C. van der Marck,A. Hogenbirk,D. van Veen 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23

Two distinct methods of propagation for basic nuclear data uncertainties to large scale systems will be presented and compared. The "Total Monte Carlo" method is using a statistical ensemble of nuclear data libraries randomly generated by means of a Monte Carlo approach with the TALYS system. These libraries are then directly used in a large number of reactor calculations (for instance with MCNP) after which the exact probability distribution for the reactor parameter is obtained. The second method makes use of available covariance files and can be done in a single reactor calculation (by using the perturbation method). In this exercise, both methods are using consistent sets of data files, which implies that covariance files used in the second method are directly obtained from the randomly generated nuclear data libraries from the first method. This is a unique and straightforward comparison allowing to directly apprehend advantages and drawbacks of each method. Comparisons for different reactions and criticality-safety benchmarks from ^(19)F to actinides will be presented. We can thus conclude whether current methods for using covariance data are good enough or not.