PS Seminar Series: RWP-RK Transcription Factor NLP2 is Required for Leghemoglobin Expression

Abstract - The physiology of legume nodules evolved as a compromise between maintaining sufficiently high rates of respiration in bacteroids to provide reductant for nitrogen fixation and the low oxygen levels required for nitrogenase function. A key component of this unique physiology is the leghemoglobins, haem-containing proteins involved in binding and/or transporting oxygen. Leghemoglobins are believed to serve as an oxygen buffer, effectively lowering the pO2 of N-fixing cells to nanomolar levels to protect the O2-sensitive nitrogenase while facilitating the diffusion of O2 to bacteroids for respiration. We have identified a gene encoding a NIN-like protein transcription factor, NLP2, that is highly expressed in the N-fixation zone of nodules and which is required for expression of leghemoglobin genes. Available evidence suggests that NLP2 regulation of leghemoglobins may reflect an ancestral role for NLPs in adaption to hypoxia.

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