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Proc Natl Acad Sci U S A. 2014 Apr 1;111(13):4814-9. doi: 10.1073/pnas.1312801111. Epub 2014 Mar 19.

Soybean SAT1 (Symbiotic Ammonium Transporter 1) encodes a bHLH transcription factor involved in nodule growth and NH4+ transport.

Author information

1
School of Agriculture Food and Wine, The University of Adelaide, Adelaide, SA 5050, Australia.

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.

KEYWORDS:

legume; nitrogen fixation; nitrogen transport

PMID:
24707045
PMCID:
PMC3977234
DOI:
10.1073/pnas.1312801111
[Indexed for MEDLINE]
Free PMC Article

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