JXB Advance Access originally published online on November 17, 2003
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Journal of Experimental Botany, Vol. 55, No. 394, pp. 43-47, January 1, 2004
© 2004 Oxford University Press
Plant Carbon-Nitrogen Interactions from Rhizospheres to Planet |
A Medicago sativa haem oxygenase gene is preferentially expressed in root nodules
Received 27 May 2003; Accepted 11 August 2003
1 Laboratoire de Biologie Végétale et Microbiologie, CNRS FRE 2294, Université de Nice-Sophia Antipolis, Parc Valrose, F-06108 Nice cédex 02, France
* To whom correspondence should be addressed. Fax: +33 4 92 07 68 38. E-mail: puppo{at}unice.fr
Haem oxygenases (HO) are ubiquitous enzymes catalysing the oxidative degradation of haem into biliverdin, iron and carbon monoxide. Whereas animal HOs participate in multiple cellular functions including haemoglobin catabolism, antioxidant defence and iron homeostasis, to date, plant HOs have so far only been involved in phytochrome metabolism. The expression of the HO1 gene was studied in Medicago sativa, especially during the interaction with its symbiotic partner, Sinorhizobium meliloti. Transcript accumulation was higher in mature root nodules than in roots and leaves and was correlated to HO1 protein immunodetection. The analysis of HO1 expression following alfalfa root inoculation with S. meliloti indicates that transcripts do not accumulate during the early steps of symbiosis, but rather in the mature nodules. These results correlate with the expression of the leghaemoglobin gene, which encodes the major haem-containing protein present in the nodule. Contrary to its animal counterpart, alfalfa HO1 was not induced by pro- oxidant compounds including H2O2, paraquat and sodium nitroprusside, suggesting that it is not involved in the antioxidant defence. The results suggest that HO1 could play a role in the alfalfa mature nodule and its involvement in leghaemoglobin metabolism is hypothesized.
Key words: Haem, leghaemoglobin, Medicago sativa, oxygenase, reactive oxygen species, symbiosis.
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