NIN: the key to nodulation

Jieyu Liu

Research output: Thesisinternal PhD, WU

Abstract

Legume-rhizobium symbiosis results in nitrogen-fixing root nodules. This symbiosis allow legumes to grow in nitrogen-poor soil. NIN (NODULE INCEPTION) is a transcription factor that essential for multiple processes of nodule formation. However, how it can play a key role in these processes, which occur in different times and locations, remain elusive. Here, we found that during nodule initiation, the regulatory sequences sufficient for the epidermal infection process are located within a -5 kb region in Medicago truncatula. Furthermore, we identified a remote upstream regulatory region, which is required for the expression of NIN in the pericycle to initiate nodule organogenesis. In mature nodule, we identified late stage Nod factor (NF) signaling controlled set of genes (including NIN). These genes turned to be markedly different from the genes activated in roots upon NF application. Moreover, by analyzing two nin weak allele mutants, nin-13/16, we found that the level of NIN in mature nodule is essential for the transition from infection to fixation zone in establishing a functional symbiosis. Besides, we showed that NIN is not functionally equivalent with its orthologues outside the nitrogen fixation clade (NFC). Further, we identified difference between NIN and its orthologues outside of the NFC. These changes are important for the function of NIN in nodule formation. In conclusion, essential changes has been introduced to NIN, allowing it plays a key role in all stages of nodule development, and its versatility depends on its spatial–temporal concentration level.

Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • Bisseling, Ton, Promotor
  • Kulikova, O., Co-promotor
  • Kohlen, Wouter, Co-promotor
Award date3 Dec 2021
Place of PublicationWageningen
Publisher
Print ISBNs9789464470031
DOIs
Publication statusPublished - 3 Dec 2021

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