Celine Mens - Molecular mechanisms in the control of legume nodulation Galina Fretter's picture

  • Datum: 27.05.2019
  • Uhrzeit: 14:00 - 15:30
  • Vortragende(r): Celine Mens
  • Ort: Central Building
  • Raum: Seminar Room
  • Gastgeber: Mark Stitt

When nitrogen availability is low, legumes are able to establish a symbiotic relationship with nitrogen-fixing rhizobia in the soil. This results in the formation of new root organs called nodules that house the bacteria providing ammonium to the plant in return for photosynthetic carbohydrates.

We use genetic, physiological and functional-genomic approaches to investigate the mechanisms driving nodule development and regulation with a focus on soybean. Cytokinin plays an important role in nodule initiation and the GmIPT biosynthesis gene family was identified completely. As nodulation is a costly process, the host has mechanisms in place to tightly regulate nodule numbers following rhizobia-inoculation (autoregulation of nodulation) and nitrate-treatment (nitrate-dependent regulation of nodulation). Both control mechanisms require the upregulation of a root-derived signal identified as CLAVATA3/ESR related (CLE) peptides. Two rhizobia-induced CLE peptides (GmRIC1 and GmRIC2) act systemically through the shoot, whereas a nitrate-induced CLE peptide (GmNIC1) acts locally in the root. Interestingly, all three CLE peptides are perceived by the same LRR receptor kinase, called Nodulation Autoregulation Receptor Kinase (NARK). This perception results in the regulation of a microRNA, i.e. miR2111, which is transported to the root where it regulates further nodule formation by targeting the mRNA of GmTML for degradation by the 26S proteasome. In addition to the nodulation-suppressing CLE peptides, the complete CLE peptide gene families were identified in soybean (84), common bean (46), Medicago truncatula (52), and Lotus japonicus (53) providing an extensive resource for the characterisation of these factors in cell growth and differentiation. This has led to the identification of two new M. truncatula CLE peptides acting in nodulation control, i.e. MtCLE34 and MtCLE35, which are both nitrogen- and rhizobia responsive. Findings relating to our progress in identifying and characterising the abovementioned molecular factors will be presented.

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