1. Soybean SAT1 (Symbiotic Ammonium Transporter 1) encodes a bHLH transcription factor involved in nodule growth and NH4+ transport.
- Author
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Chiasson DM, Loughlin PC, Mazurkiewicz D, Mohammadidehcheshmeh M, Fedorova EE, Okamoto M, McLean E, Glass AD, Smith SE, Bisseling T, Tyerman SD, Day DA, and Kaiser BN
- Subjects
- Biological Transport, Cell Membrane metabolism, DNA, Plant metabolism, Gene Expression Regulation, Plant, Protein Binding, Root Nodules, Plant cytology, Root Nodules, Plant ultrastructure, Saccharomyces cerevisiae metabolism, Glycine max genetics, Glycine max ultrastructure, Ammonium Compounds metabolism, Basic Helix-Loop-Helix Leucine Zipper Transcription Factors metabolism, Cation Transport Proteins metabolism, Root Nodules, Plant growth & development, Root Nodules, Plant metabolism, Soybean Proteins metabolism, Glycine max growth & development, Glycine max metabolism
- Abstract
Glycine max symbiotic ammonium transporter 1 was first documented as a putative ammonium (NH4(+)) channel localized to the symbiosome membrane of soybean root nodules. We show that Glycine max symbiotic ammonium transporter 1 is actually a membrane-localized basic helix-loop-helix (bHLH) DNA-binding transcription factor now renamed Glycine max bHLH membrane 1 (GmbHLHm1). In yeast, GmbHLHm1 enters the nucleus and transcriptionally activates a unique plasma membrane NH4(+) channel Saccharomyces cerevisiae ammonium facilitator 1. Ammonium facilitator 1 homologs are present in soybean and other plant species, where they often share chromosomal microsynteny with bHLHm1 loci. GmbHLHm1 is important to the soybean rhizobium symbiosis because loss of activity results in a reduction of nodule fitness and growth. Transcriptional changes in nodules highlight downstream signaling pathways involving circadian clock regulation, nutrient transport, hormone signaling, and cell wall modification. Collectively, these results show that GmbHLHm1 influences nodule development and activity and is linked to a novel mechanism for NH4(+) transport common to both yeast and plants.
- Published
- 2014
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