IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

17 th International Congress on Nitrogen Fixation
Fremantle, Western Australia
27 November – 1 December 2011
Session Details: Tuesday 29 November 2011
Concurrent Session 8 – Plant Symbiotic Genes
1600 – 1720
Authors: Brett Ferguson 1 , Dongxue Li 1 , Meng-Han Lin 1 , Satomi Hayashi 1 , Yu-Hsiang Lin 1 , Dugald
Reid 1 , Saeid Mirzaei 1 , Alina Tollenaere 1 , Peter Gresshoff 1
1 Australian Research Council Center of Excellence for Integrative Legume Research,
School of Agriculture and Food Sciences, University of Queensland, St. Lucia, Brisbane,
QLD, 4072, Australia
Presentation Title: Novel components involved in legume nodule development and autoregulation
Presentation Time: 1620 – 1640
To discover novel legume components involved in nodule formation (Ferguson et al. 2010), we used nextgeneration
sequencing (Illumina) and the available soybean genome (www.phytozome.net/soybean) to identify
genes that are differentially expressed in the zone of root hair emergence following rhizobia-inoculation.
Legumes regulate the number of nodules they form via the Autoregulation Of Nodulation (AON). Following
rhizobia-inoculation, AON commences with the production of a root-derived signal called Q (Reid et al. 2011a).
We have identified soybean Q candidate genes encoding CLAVATA3/ESR related (CLE) peptides that exhibit
increased expression following rhizobia inoculation or inhibitory nitrate treatment (Reid et al. 2011b). Overexpression
of these genes significantly reduces soybean nodule numbers. The nitrate-induced Q peptide
appears to act locally, whereas the rhizobia-induced Q peptide is transported to the shoot where it, or a product
of its action, is perceived by a LRR receptor kinase called NARK. We used next-generation sequencing to
identify soybean components acting downstream of NARK in the leaf. Candidate genes identified can now be
used in our recently established bioassay to confirm the presence of Q in various samples and biological extracts
(e.g., xylem sap). We also isolated and characterized the phenotype of a soybean line mutated in the
homeologous gene of GmNARK, GmCLAVATA1A. Following the perception of Q by NARK in the leaf, a number
of factors are produced including a novel signaling compound called the Shoot-Derived Inhibitor (SDI). SDI is
predicted to be transported from the shoot to the root where it inhibits continued nodule development. We found
SDI to be NARK- and Nod factor-dependent, heat stable, small, and likely not a peptide or RNA molecule (Lin et
al. 2010, 2011). Findings regarding our progress in identifying and characterising the abovementioned
nodulation factors will be presented.
Ferguson BJ, Indrasumunar A, Hayashi S, Lin Y-H, Lin M-H, Reid D, Gresshoff PM (2010) Molecular analysis of legume nodule
development and autoregulation. Journal of Integrative Plant Biology 52: 61-76
Lin Y-H, Ferguson BJ, Kereszt A, Gresshoff PM (2010) Suppression of hypernodulation in soybean by a leaf-extracted, NARK- and Nod
factor-dependent, low molecular mass fraction. New Phytologist 185: 1074-1086
Lin Y-H, Lin M-H, Gresshoff PM, Ferguson BJ (2011) An efficient petiole-feeding bioassay for introducing aqueous solutions into
dicotyledonous plants. Nature Protocols 6: 36-45
Reid DE, Ferguson BJ, Hayashi S, Lin Y-H, Gresshoff PM (2011a) Molecular mechanisms controlling legume autoregulation of nodulation.
Annals of Botany 108: 789-795
Reid DE, Ferguson BJ, Gresshoff PM (2011b) Inoculation- and nitrate-induced CLE peptides of soybean control NARK-dependent nodule
formation. Molecular Plant-Microbe Interactions 24: 606-618
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