NODULE INCEPTION Recruits the Lateral Root Developmental Program for Symbiotic Nodule Organogenesis in Medicago truncatula

Katharina Schiessl, Jodi L.S. Lilley, Tak Lee, Ioannis Tamvakis, Wouter Kohlen, Paul C. Bailey, Aaron Thomas, Jakub Luptak, Karunakaran Ramakrishnan, Matthew D. Carpenter, Kirankumar S. Mysore, Jiangqi Wen, Sebastian Ahnert, Veronica A. Grieneisen, Giles E.D. Oldroyd*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

20 Citations (Scopus)

Abstract

To overcome nitrogen deficiencies in the soil, legumes enter symbioses with rhizobial bacteria that convert atmospheric nitrogen into ammonium. Rhizobia are accommodated as endosymbionts within lateral root organs called nodules that initiate from the inner layers of Medicago truncatula roots in response to rhizobial perception. In contrast, lateral roots emerge from predefined founder cells as an adaptive response to environmental stimuli, including water and nutrient availability. CYTOKININ RESPONSE 1 (CRE1)-mediated signaling in the pericycle and in the cortex is necessary and sufficient for nodulation, whereas cytokinin is antagonistic to lateral root development, with cre1 showing increased lateral root emergence and decreased nodulation. To better understand the relatedness between nodule and lateral root development, we undertook a comparative analysis of these two root developmental programs. Here, we demonstrate that despite differential induction, lateral roots and nodules share overlapping developmental programs, with mutants in LOB-DOMAIN PROTEIN 16 (LBD16) showing equivalent defects in nodule and lateral root initiation. The cytokinin-inducible transcription factor NODULE INCEPTION (NIN) allows induction of this program during nodulation through activation of LBD16 that promotes auxin biosynthesis via transcriptional induction of STYLISH (STY) and YUCCAs (YUC). We conclude that cytokinin facilitates local auxin accumulation through NIN promotion of LBD16, which activates a nodule developmental program overlapping with that induced during lateral root initiation.

Original languageEnglish
Pages (from-to)3657-3668.e5
JournalCurrent Biology
Volume29
Issue number21
DOIs
Publication statusPublished - 4 Nov 2019

Keywords

  • auxin
  • CYTOKININ RESPONSE FACTOR
  • endosymbiosis
  • LATERAL ORGAN BOUNDARIES DOMAIN
  • lateral root/nodule organogenesis
  • Medicago truncatula
  • nitrogen
  • NODULE INCEPTION
  • rhizobia
  • YUCCA

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