Present address: Department of Biological Sciences, Smith College, Northampton, MA 01063, USA.
Short root mutant of Lotus japonicus with a dramatically altered symbiotic phenotype
Article first published online: 25 DEC 2001
The Plant Journal
Volume 23, Issue 1, pages 97–114, July 2000
How to Cite
Wopereis, J., Pajuelo, E., Dazzo, F. B., Jiang, Q., Gresshoff, P. M., De Bruijn, F. J., Stougaard, J. and Szczyglowski, K. (2000), Short root mutant of Lotus japonicus with a dramatically altered symbiotic phenotype. The Plant Journal, 23: 97–114. doi: 10.1046/j.1365-313x.2000.00799.x
- Issue published online: 25 DEC 2001
- Article first published online: 25 DEC 2001
- Received 21 January 2000; revised 10 April 2000; accepted 7 May 2000.
- root development;
Legume plants carefully control the extent of nodulation in response to rhizobial infection. To examine the mechanism underlying this process we conducted a detailed analysis of the Lotus japonicus hypernodulating mutants, har1-1, 2 and 3 that define a new locus, HYPERNODULATION ABERRANT ROOT FORMATION (Har1), involved in root and symbiotic development. Mutations in the Har1 locus alter root architecture by inhibiting root elongation, diminishing root diameter and stimulating lateral root initiation. At the cellular level these developmental alterations are associated with changes in the position and duration of root cell growth and result in a premature differentiation of har1-1 mutant root. No significant differences between har1-1 mutant and wild-type plants were detected with respect to root growth responses to 1-aminocyclopropane1-carboxylic acid, the immediate precursor of ethylene, and auxin; however, cytokinin in the presence of AVG (aminoetoxyvinylglycine) was found to stimulate root elongation of the har1-1 mutant but not the wild-type. After inoculation with Mesorhizobium loti, the har1 mutant lines display an unusual hypernodulation (HNR) response, characterized by unrestricted nodulation (hypernodulation), and a concomitant drastic inhibition of root and shoot growth. These observations implicate a role for the Har1 locus in both symbiotic and non-symbiotic development of L. japonicus, and suggest that regulatory processes controlling nodule organogenesis and nodule number are integrated in an overall mechanism governing root growth and development.