Short root mutant of Lotus japonicus with a dramatically altered symbiotic phenotype
Open Access
- 1 July 2000
- journal article
- research article
- Published by Wiley in The Plant Journal
- Vol. 23 (1), 97-114
- https://doi.org/10.1046/j.1365-313x.2000.00799.x
Abstract
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.Keywords
This publication has 56 references indexed in Scilit:
- HOOKLESS1, an Ethylene Response Gene, Is Required for Differential Cell Elongation in the Arabidopsis HypocotylCell, 1996
- Regulation of plant morphogenesis by Lipo‐Chitin oligosaccharidesCritical Reviews in Plant Sciences, 1996
- Autoregulation of soybean nodulation: Delayed inoculation increases nodule numberPhysiologia Plantarum, 1995
- Ethylene as a Possible Mediator of Light- and Nitrate-Induced Inhibition of Nodulation of Pisum sativum L. cv SparklePlant Physiology, 1992
- Selection and Initial Characterization of Partially Nitrate Tolerant Nodulation Mutants of SoybeanPlant Physiology, 1989
- Inhibition of legume nodule formation and N2fixation by nitrateCritical Reviews in Plant Sciences, 1988
- Growth comparisons of a supernodulating soybean (Glycine max) mutant and its wild‐type parentPhysiologia Plantarum, 1986
- A new pea mutant with efficient nodulation in the presence of nitratePlant Science Letters, 1984
- Small leguminosae as test plants for nodulation of Rhizobium leguminosarum and other rhizobia and agrobacteria harbouring a leguminosarum sym-plasmidPlant Science Letters, 1982
- Effect of Silver Ion, Carbon Dioxide, and Oxygen on Ethylene Action and MetabolismPlant Physiology, 1979