Affiliation:
1. State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China
2. Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei, China
Abstract
ABSTRACT
HetR plays a key role in regulation of heterocyst differentiation and patterning in
Anabaena
. It directly regulates genes involved in heterocyst differentiation (such as
hetP
and
hetZ
), genes involved in pattern formation (
patA
), and many others. In this study, we investigated the functional relationship of
hetP
and
hetZ
and their role in HetR-dependent cell differentiation. Coexpression of
hetP
and
hetZ
from the promoter of
ntcA
, which encodes the global nitrogen regulator, enabled a
hetR
mutant to form heterocysts with low aerobic nitrogenase activity. Overexpression of
hetZ
restored heterocyst differentiation in a
hetP
mutant and vice versa. Overexpression of
hetR
restored heterocyst formation in either a
hetP
or a
hetZ
mutant but not in a
hetZ hetP
double mutant. The functional overlap of
hetP
and
hetZ
was further confirmed by reverse transcription-quantitative PCR (RT-qPCR) and transcriptomic analyses of their effects on gene expression. In addition, yeast two-hybrid and pulldown assays showed the interaction of HetZ with HetR. HetP and HetZ are proposed as the two major factors that control heterocyst formation in response to upregulation of
hetR
.
IMPORTANCE
Heterocyst-forming cyanobacteria contribute significantly to N
2
fixation in marine, freshwater, and terrestrial ecosystems. Formation of heterocysts enables this group of cyanobacteria to fix N
2
efficiently under aerobic conditions. HetR, HetP, and HetZ are among the most important factors involved in heterocyst differentiation. We present evidence for the functional overlap of
hetP
and
hetZ
and for the key role of the HetR-HetP/HetZ circuit in regulation of heterocyst differentiation. The regulatory mechanism based on HetR, HetP, and HetZ is probably conserved in all heterocyst-forming cyanobacteria.
Funder
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences
National Natural Science Foundation of China
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
17 articles.
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