NIN is essential for development of symbiosomes, suppression of defence and premature senescence in Medicago truncatula nodules. Issue 1 (18th February 2021)

• Record Type: Journal Article
• Authors: Liu, Jieyu; Rasing, Menno; Zeng, Tian; Klein, Joël; Kulikova, Olga; Bisseling, Ton
• Is Part Of: New phytologist. Volume 230:Issue 1(2021)
• Page Start: 290
• Page End: 303
• Publication Date: 2021-02-18
• Subjects: defence -- early senescence -- Medicago truncatula -- NIN (NODULE INCEPTION) -- nodule development -- symbiosome; Botany -- Periodicals; 580
• DOI: 10.1111/nph.17215
• Languages: English
• ISSNs: 0028-646X

Abstract

Summary: NIN (NODULE INCEPTION) is a transcription factor that plays a key role during root nodule initiation. However, its role in later nodule developmental stages is unclear. Both NIN mRNA and protein accumulated at the highest level in the proximal part of the infection zone in Medicago truncatula nodules. Two nin weak allele mutants, nin‐13 / 16, form a rather normal nodule infection zone, whereas a fixation zone is not formed. Instead, a zone with defence responses and premature senescence occurred and symbiosome development gets arrested. Mutations in nin‐13 / 16 resulted in a truncated NIN lacking the conserved PB1 domain. However, this did not cause the nodule phenotype as nin mutants expressing NINΔPB1 formed wild‐type‐like nodule. The phenotype is likely to be caused by reduced NIN mRNA levels in the cytoplasm. Transcriptome analyses of nin‐16 nodules showed that expression levels of defence/senescence‐related genes are markedly increased, whereas the levels of defence suppressing genes are reduced. Although defence/senescence seems well suppressed in the infection zone, the transcriptome is already markedly changed in the proximal part of infection zone. In addition to its function in infection and nodule organogenesis, NIN also plays a major role at the transition from infection to fixation zone in establishing a functional symbiosis.