Poster: Plant Pathogen/Symbiont Interactions
Abs #
719: A leucine-rich repeat receptor-like kinase is mutated in the Medicago truncatula hypernodulating sunn mutant.
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Presenter: |
Schnabel, Elise L, eschnab@clemson.edu |
Authors | Schnabel, Elise L (A) Frugoli, Julia A (A) | | Affiliations: |
(A): Clemson University
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Legumes control the extent of symbiotic root nodule formation through an autoregulatory mechanism in which nodulating roots induce a shoot response that signals back to the roots inhibiting further nodule initiation and development. The EMS-induced sunn mutant of Medicago truncatula has a defect in this autoregulatory system developing up to 10 times more nodules than wild-type plants. As in most other legume hypernodulation mutants, this root phenotype is determined by the genotype of the shoot suggesting that the SUNN is involved in the shoot control of nodulation. The sunn locus maps to the short arm of chromosome 4 and is tightly linked to the DNABP CAPS marker with no recombination events between the sunn locus and DNABP in a mapping population of 287 F2 progeny. A 400 kb BAC contig spanning the region between flanking recombination events was assembled and the sequence of ~260 kb of this region was screened for candidate genes. A single base change was detected in the sunn mutant in a leucine-rich repeat receptor-like kinase (LRR-RLK) gene with a high degree of similarity to the Arabidopsis CLAVATA1 gene and to LRR-RLK genes recently discovered to be involved in nodulation regulation in Lotus japonicus (HAR1) and soybean (NARK). The resulting Arg to Lys change is at a position in the kinase domain which is invariant in all characterized serine/threonine and tyrosine protein kinases. We speculate that SUNN may be directly involved in responding to the root-derived signal via the LRR domain and triggering the shoot response via the interaction of the kinase domain with other proteins. The downstream effects of the sunn mutation on gene expression in roots are being explored. This work was supported by USDA 2002-02656.
