Submitted to: Iron Nutrition and Interactions in Plants Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 7/30/1997
Publication Date: N/A
Interpretive Summary: Interpretive Summary not needed for this 115.
Technical Abstract: The root plasmalemma-localized Fe(III) reductase is an important system utilized by dicotyledonous and other Strategy I plants to reduce rhizospheric Fe(III)-chelates to Fe2+ and thereby enable the root influx of Fe. In fact, the reductase appears to be the physiological rate-limiting step in overall Fe acquisition, and thus the regulation of its activity should be closely linked to whole-plant Fe requirements. Because both vegetative and reproductive tissues require Fe in varying amounts, the plant's total Fe needs may vary spatially throughout the shoot as well as temporally throughout plant development. Somehow the shoot tissues must communicate their Fe needs to the roots in order to ensure adequate, but not excessive, Fe delivery. We suggest that this homeostatic coordination of Fe nutrition is achieved through shoot-to-root communication via the phloem. The phloem pathway has long been recognized as a long-distance conduit for nutrients from source to sink regions throughout the plant. I recent years, however, the phloem also has been recognized as a potential network for the trafficking of information molecules. These molecules may include small peptides, large proteins, or even mRNA which could serve to communicate information regarding physiological/nutritional aspects of a source region and could elicit responses or alterations in a downstream sink region. Evidence has existed for a number of years that the root Fe(III) reductase and other Strategy I processes can be up-regulated by phloem-mobile molecules delivered to the roots. More recently, we have utilized novel Fe hyper-accumulating pea mutants to show that a shoot-generated, phloem-mobile compound serves as a promotive signal for these root Fe acquisition processes.