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Defective Long-Distance Auxin Transport Regulation in the Medicago truncatula super numeric nodules Mutant


van Noorden, GE and Ross, JJ and Reid, JB and Rolfe, BG and Mathesius, U, Defective Long-Distance Auxin Transport Regulation in the Medicago truncatula super numeric nodules Mutant, Plant Physiology, 140, (4) pp. 1494-1506. ISSN 0032-0889 (2006) [Refereed Article]

DOI: doi:10.1104/pp.105.075879


Long-distance auxin transport was examined in Medicago truncatula and in its supernodulating mutant sunn (super numeric nodules) to investigate the regulation of auxin transport during autoregulation of nodulation (AON). A method was developed to monitor the transport of auxin from the shoot to the root in whole seedlings. Subsequently, the transport was monitored after inoculation of roots with the nodulating symbiont Sinorhizobium meliloti. The sunn mutant showed an increased amount of auxin transported from the shoot to the root compared to the wild type. The auxin transport capacity of excised root segments was similar in wild type and sunn, suggesting that the difference in long-distance auxin transfer between them is due to loading in the shoot. After inoculation, wild-type seedlings showed decreased auxin loading from the shoot to the root; however, the sunn mutant failed to reduce the amount of auxin loaded. The time of reduced auxin loading correlated with the onset of AON. Quantification of endogenous auxin levels at the site of nodule initiation showed that sunn contained three times more auxin than wild type. Inoculation of sunn failed to reduce the level of auxin within 24 h, as was observed in the wild type. We propose a model for the role of auxin during AON of indeterminate legumes: 1) high levels of endogenous auxin are correlated with increased numbers of nodules, 2) inoculation of roots reduces auxin loading from the shoot to the root, and 3) subsequent reduction of auxin levels in the root inhibits further nodule initiation. © 2006 American Society of Plant Biologists.

Item Details

Item Type:Refereed Article
Research Division:Biological Sciences
Research Group:Plant biology
Research Field:Plant physiology
Objective Division:Plant Production and Plant Primary Products
Objective Group:Environmentally sustainable plant production
Objective Field:Environmentally sustainable plant production not elsewhere classified
UTAS Author:Ross, JJ (Associate Professor John Ross)
UTAS Author:Reid, JB (Professor Jim Reid)
ID Code:40330
Year Published:2006
Web of Science® Times Cited:165
Deposited By:Plant Science
Deposited On:2006-08-01
Last Modified:2007-05-04

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