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Abstract Background Nuclear endosperm development is a common mechanism among Angiosperms, including Arabidopsis. During nuclear development, the endosperm nuclei divide rapidly after fertilization without cytokinesis to enter the syncytial phase, which is then followed by the cellularized phase. The endosperm can be divided into three spatial domains with distinct functions: the micropylar, peripheral, and chalazal domains. Previously, we identified two putative small invertase inhibitors, InvINH1 and InvINH2, that are specifically expressed in the micropylar region of the syncytial endosperm. In addition, ectopically expressing InvINH1 in the cellularized endosperm led to a reduction in embryo growth rate. However, it is not clear what are the upstream regulators responsible for the specific expression of InvINHs in the syncytial endosperm. Results Using protoplast transient expression system, we discovered that a group of type I MADS box transcription factors can form dimers to activate InvINH1 promoter. Promoter deletion assays carried out in the protoplast system revealed the presence of an enhancer region in InvINH1 promoter, which contains several consensus cis-elements for the MADS box proteins. Using promoter deletion assay in planta , we further demonstrated that this enhancer region is required for InvINH1 expression in the syncytial endosperm. One of the MADS box genes, AGL62, is a key transcription factor required for syncytial endosperm development. Using promoter-GFP reporter assay, we demonstrated that InvINH1 and InvINH2 are not expressed in agl62 mutant seeds. Collectively, our data supports the role of AGL62 and other type I MADS box genes as the upstream activators of InvINHs expression in the syncytial endosperm. Conclusions Our findings revealed several type I MADS box genes that are responsible for activating InvINH1 in the syncytial endosperm, which in turn regulates embryo growth rate during early stage of seed development.
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This content will become publicly available on April 24, 2026
Regulation of the promoter for capsular polysaccharide synthesis in Neisseria meningitidis serogroup B by HTH_XRE family transcription factor
The capsular polysaccharide synthesis (cps) locus of Neisseria meningitidis is implicated in invasive meningococcal disease. The synthesis (synABCD) and transport (ctrABCD) operons are transcribed in opposite directions from a common intergenic region, and the expression is negatively regulated by the bacterial two-component system (TCS) misR/misS and thermosensitive RNA folding. However, these mechanisms do not fully explain the stationary phase responses, and the cis-acting elements remain to be fully characterized. Using the GFP reporter gene and site-directed mutagenesis, cis-regulatory elements in the 134 bp intergenic region, NmIR, were investigated. While confirming a known RpoD promoter, an additional potential promoter element and putative binding sites for the transcription factors fis and lexA were identified through sequence analysis. Deletion of the putative lexA binding site led to an increase in GFP fluorescence. The N. meningitidis genome carries only one lexA homolog, the helix-turn-helix regulator XRE family member (GenBank-NMB0910, HTH_XRE). Trans-complementation of the NmIR-GFP reporter with the N. meningitidis HTH_XRE expression plasmid led to increased fluorescence. Trans-complementation with either misR/misS or nusG decreased reporter gene expression. Consistent with previous reports, deletion of the RpoD promoter reduced expression by 50%, suggesting the redundancy of promoter elements in the intergenic region. Thus, the results confirm the functioning of an exogenous N. meningitidis capsule synthesis promoter in Escherichia coli and demonstrate its regulation through trans-complementation by misR/misS, HTH_XRE, and nusG.
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- Award ID(s):
- 2100978
- PAR ID:
- 10594321
- Editor(s):
- Atack, John M
- Publisher / Repository:
- American Society for Microbiology
- Date Published:
- Journal Name:
- Microbiology Spectrum
- ISSN:
- 2165-0497
- Subject(s) / Keyword(s):
- HTH_XRE transcription factor, cis-regulatory elements, capsular polysaccharides synthesis, two-component regulatory systems, Neisseria meningitidis, misR/misS, NusG, CrgA, transcription factors, RpoD
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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