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Abstract The regulation of floral organ identity was investigated using a forward genetic approach in five floral homeotic mutants ofThalictrum, a noncore eudicot. We hypothesized that these mutants carry defects in the floral patterning genes. Mutant characterization comprised comparative floral morphology and organ identity gene expression at early and late developmental stages, followed by sequence analysis of coding and intronic regions to identify transcription factor binding sites and protein–protein interaction (PPI) motifs. Mutants exhibited altered expression of floral MADS‐box genes, which further informed the function of paralogs arising from gene duplications not found in reference model systems. The ensuing modified BCE models for the mutants supported instances of neofunctionalization (e.g., B‐class genes expressed ectopically in sepals), partial redundancy (E‐class), or subfunctionalization (C‐class) of paralogs. A lack of deleterious mutations in the coding regions of candidate floral MADS‐box genes suggested thatcis‐regulatory ortrans‐acting mutations are at play. Consistent with this hypothesis, double‐flower mutants had transposon insertions or showed signs of transposon activity in the regulatory intron ofAGAMOUS(AG) orthologs. Single amino acid substitutions were also found, yet they did not fall on any of the identified DNA binding or PPI motifs. In conclusion, we present evidence suggesting that transposon activity and regulatory mutations in floral homeotic genes likely underlie the striking phenotypes of theseThalictrumfloral homeotic mutants.
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Hox proteins interact to pattern neuronal subtypes in Caenorhabditis elegans males
Abstract Hox transcription factors are conserved regulators of neuronal subtype specification on the anteroposterior axis in animals, with disruption of Hox gene expression leading to homeotic transformations of neuronal identities. We have taken advantage of an unusual mutation in the Caenorhabditis elegans Hox gene lin-39, lin-39(ccc16), which transforms neuronal fates in the C. elegans male ventral nerve cord in a manner that depends on a second Hox gene, mab-5. We have performed a genetic analysis centered around this homeotic allele of lin-39 in conjunction with reporters for neuronal target genes and protein interaction assays to explore how LIN-39 and MAB-5 exert both flexibility and specificity in target regulation. We identify cis-regulatory modules in neuronal reporters that are both region-specific and Hox-responsive. Using these reporters of neuronal subtype, we also find that the lin-39(ccc16) mutation disrupts neuronal fates specifically in the region where lin-39 and mab-5 are coexpressed, and that the protein encoded by lin-39(ccc16) is active only in the absence of mab-5. Moreover, the fates of neurons typical to the region of lin-39-mab-5 coexpression depend on both Hox genes. Our genetic analysis, along with evidence from Bimolecular Fluorescence Complementation protein interaction assays, supports a model in which LIN-39 and MAB-5 act at an array of cis-regulatory modules to cooperatively activate and to individually activate or repress neuronal gene expression, resulting in regionally specific neuronal fates.
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- Award ID(s):
- 1827514
- PAR ID:
- 10574247
- Editor(s):
- Hobert, O
- Publisher / Repository:
- Oxford
- Date Published:
- Journal Name:
- Genetics
- Volume:
- 220
- Issue:
- 4
- ISSN:
- 1943-2631
- Page Range / eLocation ID:
- 1-14
- Subject(s) / Keyword(s):
- Caenorhabditis elegans Hox genes neurogenesis TALE homeodomain proteins male-specific neurons ventral cord neurons BiFC
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/genetics/iyac010
