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Two Hemoglobin Genes in Arabidopsis thaliana: The Evolutionary Origins of Leghemoglobins

Ben Trevaskis, Richard. A. Watts, Carol R. Andersson, Danny J. Llewellyn, Mark S. Hargrove, John S. Olson, Elizabeth S. Dennis and W. James Peacock
Proceedings of the National Academy of Sciences of the United States of America
Vol. 94, No. 22 (Oct. 28, 1997), pp. 12230-12234
Stable URL: http://www.jstor.org/stable/43046
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Two Hemoglobin Genes in Arabidopsis thaliana: The Evolutionary Origins of Leghemoglobins
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Abstract

We cloned two hemoglobin genes from Arabidopsis thaliana. One gene, AHB1, is related in sequence to the family of nonsymbiotic hemoglobin genes previously identified in a number of plant species (class 1). The second hemoglobin gene, AHB2, represents a class of nonsymbiotic hemoglobin (class 2) related in sequence to the symbiotic hemoglobin genes of legumes and Casuarina. The properties of these two hemoglobins suggest that the two families of nonsymbiotic hemoglobins may differ in function from each other and from the symbiotic hemoglobins. AHB1 is induced, in both roots and rosette leaves, by low oxygen levels. Recombinant AHB1 has an oxygen affinity so high as to make it unlikely to function as an oxygen transporter. AHB2 is expressed at a low level in rosette leaves and is low temperature-inducible. AHB2 protein has a lower affinity for oxygen than AHB1 but is similar to AHB1 in having an unusually low, pH-sensitive oxygen off-rate.

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