Affiliation:
1. Key Laboratory of Soil Microbiology of Agriculture Ministry and College of Biological Sciences, China Agricultural University , Beijing, China
Abstract
ABSTRACT
Paenibacillus polymyxa
WLY78, a N
2
-fixing bacterium, has great potential use as a biofertilizer in agriculture. Recently, we have revealed that GlnR positively and negatively regulates the transcription of the
nif
(
ni
trogen
f
ixation) operon (
nifBHDKENXhesAnifV
) in
P. polymyxa
WLY78 by binding to two loci of the
nif
promoter according to nitrogen availability. However, the regulatory mechanisms of nitrogen metabolism mediated by GlnR in the
Paenibacillus
genus remain unclear. In this study, we have revealed that glutamine synthetase (GS) and GlnR in
P. polymyxa
WLY78 play a key role in the regulation of nitrogen metabolism.
P. polymyxa
GS (encoded by
glnA
within
glnRA
) and GS1 (encoded by
glnA1
) belong to distinct groups: GSI-α and GSI-β. Both GS and GS1 have the enzyme activity to convert NH
4
+
and glutamate into glutamine, but only GS is involved in the repression by GlnR. GlnR represses transcription of
glnRA
under excess nitrogen, while it activates the expression of
glnA1
under nitrogen limitation. GlnR simultaneously activates and represses the expression of
amtBglnK
and
gcvH
in response to nitrogen availability. Also, GlnR regulates the expression of
nasA, nasD1D2, nasT, glnQHMP,
and
glnS
.
IMPORTANCE
In this study, we have revealed that
Paenibacillus polymyxa
GlnR uses multiple mechanisms to regulate nitrogen metabolism. GlnR activates or represses or simultaneously activates and inhibits the transcription of nitrogen metabolism genes in response to nitrogen availability. The multiple regulation mechanisms employed by
P. polymyxa
GlnR are very different from
Bacillus subtilis
GlnR which represses nitrogen metabolism under excess nitrogen. Both GS encoded by
glnA
within the
glnRA
operon and GS1 encoded by
glnA1
in
P. polymyxa
WLY78 are involved in ammonium assimilation, but only GS is required for regulating GlnR activity. The work not only provides significant insight into understanding the interplay of GlnR and GS in nitrogen metabolism but also provides guidance for improving nitrogen fixation efficiency by modulating nitrogen metabolism.
Funder
MOST | National Key Research and Development Program of China
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology