Knock-out of Arabidopsis metal transporter gene IRT1 results in iron deficiency accompanied by cell differentiation defects

IRT1 and IRT2 are members of the Arabidopsis ZIP metal transporter family that are specifically induced by iron deprivation in roots and act as heterologous suppressors of yeast mutations inhibiting iron and zinc uptake. Although IRT1 and IRT2 are thought to perform redundant functions as root-specific metal transporters, insertional inactivation of the IRT1 gene alone results in typical symptoms of iron deficiency causing severe leaf chlorosis and lethality in soil. The irt1 mutation is characterized by specific developmental defects, including a drastic reduction of chloroplast thylakoid stacking into grana and lack of palisade parenchyma differentiation in leaves, reduced number of vascular bundles in stems, and irregular patterns of enlarged endodermal and cortex cells in roots. Pulse labeling with 59Fe through the root system shows that the irt1 mutation reduces iron accumulation in the shoots. Short-term labeling with 65Zn reveals no alteration in spatial distribution of zinc, but indicates a lower level of zinc accumulation. In comparison to wild-type, the irt1 mutant responds to iron and zinc deprivation by altered expression of certain zinc and iron transporter genes, which results in the activation of ZIP1 in shoots, reduction of ZIP2 transcript levels in roots, and enhanced expression of IRT2 in roots. These data support the conclusion that IRT1 is an essential metal transporter required for proper development and regulation of iron and zinc homeostasis in Arabidopsis.

(Table 19, page 199) Minor constituents of one of the San Clemente iron concretions and its metallic core

The chemical and mineralogical composition of pelagic sediments from the East Pacific Ocean has been determined with the aim of defining the ultimate sources and the mechanisms of formation of the solid phases. The distribution of elements between sea-water, the pore solution and the various solid components of the sediments permits interpretations of the variations in time and space of the gross chemical composition of pelagic clays. For example, manganese, present in sea-water in a divalent form, is apparently oxidized at the sediment-water interface to tetravalent species which subsequently become a part of the group of ferromanganese oxide minerals which are found in the marine environment. It is suggested the rate of manganese accumulation in sediments is some function of the length of time the sediment surface is in contact with sea-water. The contribution of chemical species from the different geospheres is considered. The quantitative importance of pelagic clays in the major sedimentary cycle is studied on the basis of the distribution of the weathered igneous rock products between continental and pelagic deposits and sea-water. These analyses of a wide variety of pelagic clays allow a reformulation of the geochemical balance and it is concluded that pelagic clays account for approximately 13 per cent of the total mass of sediments produced over geologic time.

Motor vehicle defects and recall campaigns.

Mode of access: Internet.

A study to determine the relationship between vehicle defects and crashes. Interim report.

National Highway Traffic Safety Administration, Washington, D.C.

Study to determine the relationship between vehicle defects and failures, and vehicle crashes. Volume 2. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Correlation of braking system defects and performance inspection. Volume II: technical report. Final report.

Mode of access: Internet.

Correlation of braking system defects and performance inspection. Volume I: summary report.

National Highway Traffic Safety Administration, Washington, D.C.

Corrosion evaluation of epoxy-coated, metallic-clad and solid metallic reinforcing bars in concrete /

"December 1998."

The new university for London; a guide to its history and a criticism of its defects,

Mode of access: Internet.

Classification of safety appliance defects to be reported by federal inspectors : July 1, 1911 /

At head of title: Interstate Commerce Commission.

The use of backscattered gamma rays for evaluating defects in logs and trees /

"Contract No. AT-(40-1)-2513."

Discontinuity stresses in metallic pressure vessels.

Cover title.

Economic effects of metallic corrosion in the United States.

Appendix C published in PB-279 430.

A free examination of the common methods employed to prevent the growth of popery : in which are pointed out their defects and errors, and the advantages they give papists.

Mode of access: Internet.