Improved Protocols For Isolated Microspore Culture Of Rice. Application Of Molecular Approaches To Rice Improvement.

A summary of this work is provided. The remainder of the original report has been withheld from publication as the information contained therein should be regarded as “commercial in confidence”. The main objectives of this project were (a) to develop a microspore culture based rapid breeding system (b) to understand the genetic basis of cold tolerance and (c) achieve genetic improvements in the cold tolerance of Australian rice germplasm. Thanks to the establishment of a special linkage with researchers in the Peoples Republic of China, some excellent cold tolerant germplasm was introduced into Australia. The cold tolerance of this germplasm has been confirmed by cold treatments under glasshouse conditions. This germplasm was then provided to several breeding, genetic, and physiological research groups within the CRC. Crossing has also been carried out between this germplasm and elite Australian cultivars in order to deliver doubled haploid plants for cold tolerance breeding and genetic research. Doubled haploid (DH) plant production is a way of rapidly fixing genetic segregation in the early generations of a crossing program, thereby reducing the number of years required for the establishment of pure breeding lines. Typically, DH plants of rice are normally produced by anther culture. As a result of this procedure, we have released over one hundred DH plants from a cross between the cold tolerant American cultivar M103 and the cold sensitive Australian cultivar Doongara. However, anther culture is a low efficiency system in that it is difficult to produce large numbers of DH plants. Microspore culture, on the other hand, is a highly efficient system which isolates young pollen from anthers, and gives rise to large numbers of DH plants in crops such as canola and barley. Microspore culture has also been reported in rice; however its efficiency of production has left much to be desired, especially with respect to cultivar response ..

On the dynamics of the irreversible Michaelis-Menten reaction mechanism

The mass action kinetic model of the irreversible Michaelis-Menten reaction mechanism is mathematically intractable: an explicit analytical solution cannot be obtained. This difficulty is overcome by applying simplifying kinetic assumptions but a full understanding of their dynamic implications and applicability is not readily available. This paper shows how simple modal analysis can provide both a conceptually appealing insight into the reaction dynamics and justification of the commonly used quasi-steady-state and quasi-equilibrium assumptions.The key results are that the quasi-steady-state assumption is applicable when the initial enzyme concentration, e0, is much smaller than the Michaelis constant, Km, or when the initial substrate concentration, s0, is much greater than Km. These results show that the commonly accepted criterion e0 s0 is incomplete and should be decomposed into e0 Km and Km s0. The quasi-equilibrium assumption is valid when e0 >>>> Km and when the rate of product formation is much slower than reversion to the substrate from the intermediate state, or k2 >>>> k-1. The important dimensionless parameter ratios characterizing the reaction dynamics are e0/Km, s0/Km and k2/k-1.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26960/1/0000527.pd

Markovian Dynamics on Complex Reaction Networks

Complex networks, comprised of individual elements that interact with each other through reaction channels, are ubiquitous across many scientific and engineering disciplines. Examples include biochemical, pharmacokinetic, epidemiological, ecological, social, neural, and multi-agent networks. A common approach to modeling such networks is by a master equation that governs the dynamic evolution of the joint probability mass function of the underling population process and naturally leads to Markovian dynamics for such process. Due however to the nonlinear nature of most reactions, the computation and analysis of the resulting stochastic population dynamics is a difficult task. This review article provides a coherent and comprehensive coverage of recently developed approaches and methods to tackle this problem. After reviewing a general framework for modeling Markovian reaction networks and giving specific examples, the authors present numerical and computational techniques capable of evaluating or approximating the solution of the master equation, discuss a recently developed approach for studying the stationary behavior of Markovian reaction networks using a potential energy landscape perspective, and provide an introduction to the emerging theory of thermodynamic analysis of such networks. Three representative problems of opinion formation, transcription regulation, and neural network dynamics are used as illustrative examples.Comment: 52 pages, 11 figures, for freely available MATLAB software, see http://www.cis.jhu.edu/~goutsias/CSS%20lab/software.htm

Study protocol: Our Cultures Count, the Mayi Kuwayu Study, a national longitudinal study of Aboriginal and Torres Strait Islander wellbeing

Introduction Aboriginal and Torres Strait Islander peoples are Australia’s first peoples and have been connected to the land for ≥65 000 years. Their enduring cultures and values are considered critical to health and wellbeing, alongside physical, psychological and social factors. We currently lack large-scale data that adequately represent the experiences of Aboriginal and Torres Strait Islander people; the absence of evidence on cultural practice and expression is particularly striking, given its foundational importance to wellbeing.This work was supported by the Lowitja Institute (grant number: 1344) and the National Health and Medical Research Council of Australia (NHMRC, grant number: 1122274). RL and EB are supported by the NHMRC (references: 1088366 and 1042717, respectively). KAT is supported by the Lowitja Institute (reference: 1344). RJ is supported by an Australian Government Research Training Program (RTP) scholarship

An efficient algorithm for the stochastic simulation of the hybridization of DNA to microarrays

<p>Abstract</p> <p>Background</p> <p>Although oligonucleotide microarray technology is ubiquitous in genomic research, reproducibility and standardization of expression measurements still concern many researchers. Cross-hybridization between microarray probes and non-target ssDNA has been implicated as a primary factor in sensitivity and selectivity loss. Since hybridization is a chemical process, it may be modeled at a population-level using a combination of material balance equations and thermodynamics. However, the hybridization reaction network may be exceptionally large for commercial arrays, which often possess at least one reporter per transcript. Quantification of the kinetics and equilibrium of exceptionally large chemical systems of this type is numerically infeasible with customary approaches.</p> <p>Results</p> <p>In this paper, we present a robust and computationally efficient algorithm for the simulation of hybridization processes underlying microarray assays. Our method may be utilized to identify the extent to which nucleic acid targets (e.g. cDNA) will cross-hybridize with probes, and by extension, characterize probe robustnessusing the information specified by MAGE-TAB. Using this algorithm, we characterize cross-hybridization in a modified commercial microarray assay.</p> <p>Conclusions</p> <p>By integrating stochastic simulation with thermodynamic prediction tools for DNA hybridization, one may robustly and rapidly characterize of the selectivity of a proposed microarray design at the probe and "system" levels. Our code is available at <url>http://www.laurenzi.net</url>.</p

Milan Kundera face à l'oubli de l'être. Étude sur <i>L'immortalité</i> et <i>L'ignorance</i>

Cette époque, marquée par l'omniprésence de la technologie, de la rentabilité, de la vitesse, n'est guère réjouissante pour l'art. Ce domaine s'inscrit en effet, à l'inverse, dans une perspective de plaisir, de lenteur et de complexité. Les deux romans qui nous intéressent voguent donc à contre-courant. Or, c'est précisément parce qu'ils vont à l'encontre de « l'esprit du temps » que Milan Kundera les pense « utiles ». Il faut, pour comprendre cela, définir précisément « l'esprit du temps » et « l'esprit du roman ». Il s'agit donc d'envisager la relation de ces deux œuvres à la société postmoderne. Comment L'immortalité et L'ignorance, en faisant le constat d'une nouvelle situation existentielle, celle des « paradoxes terminaux » et de la postmodernité, permettent-ils d'appréhender de façon neuve le monde et l'existence ? Finalement, comment « l'esprit du roman » vit-il son désaccord avec le nouvel « air du temps »