NIN-like protein transcription factors regulate leghemoglobin genes in legume nodules

Journal article

Leghemoglobins enable the endosymbiotic fixation of molecular nitrogen (N₂) in legume nodules by channeling O₂ for bacterial respiration while maintaining a micro-oxic environment to protect O₂-sensitive nitrogenase. We found that the NIN-like protein (NLP) transcription factors NLP2 and NIN directly activate the expression of leghemoglobins through a promoter motif, resembling a “double” version of the nitrate-responsive elements (NREs) targeted by other NLPs, that has conserved orientation and position across legumes. CRISPR knockout of the NRE-like element resulted in strongly decreased expression of the associated leghemoglobin. Our findings indicate that the origins of the NLP-leghemoglobin module for O₂ buffering in nodules can be traced to an ancient pairing of NLPs with nonsymbiotic hemoglobins that function in hypoxia.

Authors: Jiang, S; Jardinaud, M-F; Gao, J; Pecrix, Y; Wen, J

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Association for the Advancement of Science
• Journal: Science
• Volume: 374
• Issue: 6567
• Pages: 625-628
• Publication date: 2021-10-28
• Acceptance date: 2021-09-16
• DOI: 10.1126/science.abg5945
• EISSN: 1095-9203
• ISSN: 0036-8075
• Pmid: 34709882
• Language: English
• Keywords: generic health relevance; plant proteins; nitrogen fixation; leghemoglobin; genetics; genetic promoter regions; symbiosis; plant root nodulation; Fabaceae; oxygen; plant root nodules; Medicago truncatula; plant gene expression regulation; transcription factors