Start of Arabidopsis research in Japan: a personal memoir of the seedling stage 1985–2000

The author received the research award from the Botanical Society of Japan in September 2009 under the title Development of Plant Molecular Biology using Arabidopsis. Here, the author summarizes the motivations and efforts of researchers at the start and subsequent expansion of Arabidopsis research in Japan. Pioneering study that focused on Arabidopsis characteristics started in the 1960s but it did not expand until the mid-1980s when several research groups started their studies with the new and clear objectives of examining the characteristics and capacity of multi-cellular plants by use of a molecular genetics approach. Together, members of these research groups helped to promote the novel research field, and established a nationwide system encouraging students and young researchers to join in Arabidopsis research, and supporting them scientifically and financially.     

A Study on the Transfer of Iron in Soil–Plant–Animal Continuum Under Semi-arid Environmental Conditions in Sargodha,Pakistan

The present investigation on the iron (Fe) transfer from soil to plant and in turn to animal (cows), as a function of sampling periods was conducted at the Livestock Experimental Station Sargodha, Pakistan which falls under semi-arid conditions. Although the iron transfer from soil to forage increased consistently, the forage Fe content decreased progressively with increase in sampling period. Highest Fe transfer from forage to cow blood plasma was observed during October and lowest during January. The transfer of Fe from forage to animal milk was maximum during the months of October and January and minimum during December. The transfer of Fe to plasma and milk was found to be dependent variably on the growth stage of forage in this investigation. Based on the findings of the present study, it is evident that mineral supplementation with higher Fe availability is urgently warranted to the animals particularly during the months of December and January to enhance plasma Fe in the cows being reared at that livestock farm during the entire grazing period. Thus, obligatory supplementation of Fe to the ruminants is highly recommended. Since the processes involved in iron management system in humans, animals, and plants are basically similar, appropriate elemental management must be provided to the living organisms, otherwise deficient or excessive levels of iron may deteriorate the developing cells of the organisms.     

Modeling T Cell Proliferation and Death in Vitro Based on Labeling Data: Generalizations of the Smith–Martin Cell Cycle Model

The fluorescent dye carboxyfluorescein diacetate succinimidyl ester (CFSE) classifies proliferating cell populations into groups according to the number of divisions each cell has undergone (i.e., its division class). The pulse labeling of cells with radioactive thymidine provides a means to determine the distribution of times of entry into the first cell division. We derive in analytic form the number of cells in each division class as a function of time based on the distribution of times to the first division. Choosing the distribution of time to the first division to fit thymidine labeling data for T cells stimulated in vitro under different concentrations of IL-2, we fit CFSE data to determine the dependence of T cell kinetic parameters on the concentration of IL-2. As the concentration of IL-2 increases, the average cell cycle time is shortened, the death rate of cells is decreased, and a higher fraction of cells is recruited into division. We also find that if the average cell cycle time increases with division class then the qualify of our fit to the data improves.     

The Role of Wheat Germ Agglutinin in Plant–Bacteria Interactions: A Hypothesis and the Evidence in Its Support

Wheat plants are known to develop the associative symbiosis with the rhizobacterium Azospirillum brasilense.We studied the interaction of a lectin, wheat germ agglutinin (WGA), which is also found in wheat roots, with A. brasilense, strain sp245. When added to the azospirillum culture to the final concentration of 10^–8to 10^–9M, WGA enhanced IAA production, dinitrogen fixation, and ammonium excretion by bacterial cells. WGA also promoted the synthesis of proteins, both new and those already present in bacterial cells. The hypothesis that WGA is a signal molecule rerouting the bacterial metabolism in the direction favorable for the growth and development of the host plant has been put forward. It is suggested that signal properties of WGA are the basis for one of the functions of this lectin and essential for the effective associative symbiosis.     

Biotic effects of the Chicxulub impact,K–T catastrophe and sea level change in Texas

Biotic effects of the Chicxulub impact, the K–T event and sea level change upon planktic foraminifera were evaluated in a new core and outcrops along the Brazos River, Texas, about 1000 km from the Chicxulub impact crater on Yucatan, Mexico. Sediment deposition occurred in a middle neritic environment that shallowed to inner neritic depths near the end of the Maastrichtian. The sea level fall scoured submarine channels, which were infilled by a sandstone complex with reworked Chicxulub impact spherules and clasts with spherules near the base. The original Chicxulub impact ejecta layer was discovered 45–60 cm below the sandstone complex, and predates the K–T mass extinction by about 300,000 years.Results show that the Chicxulub impact caused no species extinctions or any other significant biotic effects. The subsequent sea level fall to inner neritic depth resulted in the disappearance of all larger (> 150 μm) deeper dwelling species creating a pseudo-mass extinction and a survivor assemblage of small surface dwellers and low oxygen tolerant taxa. The K–T boundary and mass extinction was identified 40–80 cm above the sandstone complex where all but some heterohelicids, hedbergellids and the disaster opportunistic guembelitrids went extinct, coincident with the evolution of first Danian species and the global δ¹³C shift. These data reveal that sea level changes profoundly influenced marine assemblages in near shore environments, that the Chicxulub impact and K–T mass extinction are two separate and unrelated events, and that the biotic effects of this impact have been vastly overestimated.