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Abstract AGAMOUS-Like 18 (AGL18) is a MADS domain transcription factor (TF) that is structurally related to AGL15. Here we show that, like AGL15, AGL18 can promote somatic embryogenesis (SE) when ectopically expressed in Arabidopsis (Arabidopsis thaliana). Based on loss-of-function mutants, AGL15 and AGL18 have redundant functions in developmental processes such as SE. To understand the nature of this redundancy, we undertook a number of studies to look at the interaction between these factors. We studied the genome-wide direct targets of AGL18 to characterize its roles at the molecular level using chromatin immunoprecipitation (ChIP)-SEQ combined with RNA-SEQ. The results demonstrated that AGL18 binds to thousands of sites in the genome. Comparison of ChIP-SEQ data for AGL15 and AGL18 revealed substantial numbers of genes bound by both AGL15 and AGL18, but there were also differences. Gene ontology analysis revealed that target genes were enriched for seed, embryo, and reproductive development as well as hormone and stress responses. The results also demonstrated that AGL15 and AGL18 interact in a complex regulatory loop, where AGL15 inhibited transcript accumulation of AGL18, while AGL18 increased AGL15 transcript accumulation. Co-immunoprecipitation revealed an interaction between AGL18 and AGL15 in somatic embryo tissue. The binding and expression analyses revealed a complex crosstalk and interactions among embryo TFs and their target genes. In addition, our study also revealed that phosphorylation of AGL18 and AGL15 was crucial for the promotion of SE.
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The EAR Motif in the Arabidopsis MADS Transcription Factor AGAMOUS-Like 15 Is Not Necessary to Promote Somatic Embryogenesis
AGAMOUS-like 15 (AGL15) is a member of the MADS domain family of transcription factors (TFs) that can directly induce and repress target gene expression, and for which promotion of somatic embryogenesis (SE) is positively correlated with accumulation. An ethylene-responsive element binding factor-associated amphiphilic repression (EAR) motif of form LxLxL within the carboxyl-terminal domain of AGL15 was shown to be involved in repression of gene expression. Here, we examine whether AGL15′s ability to repress gene expression is needed to promote SE. While a form of AGL15 where the LxLxL is changed to AxAxA can still promote SE, another form with a strong transcriptional activator at the carboxy-terminal end, does not promote SE and, in fact, is detrimental to SE development. Select target genes were examined for response to the different forms of AGL15.
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- Award ID(s):
- 1656380
- PAR ID:
- 10318402
- Date Published:
- Journal Name:
- Plants
- Volume:
- 10
- Issue:
- 4
- ISSN:
- 2223-7747
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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AGAMOUS-like 15 (AGL15) is a member of the MADS-domain transcription factor (TF) family. MADS proteins are named for a conserved domain that was originally from an acronym derived from genes expressed in a variety of eukaryotes (MCM1-AGAMOUS-DEFICIENS-SERUM RESPONSE FACTOR). In plants, this family has expanded greatly, with more than one-hundred members generally found in dicots, and the proteins encoded by these genes have often been associated with developmental identity. AGL15 transcript and protein accumulate primarily in embryos and has been found to promote an important process called plant regeneration via somatic embryogenesis (SE). To understand how this TF performs this function, we have previously used microarray technologies to assess direct and indirect responsive targets of this TF. We have now revisited this question using next generation sequencing (NGS) to both characterize in vivo binding sites for AGL15 as well as response to the accumulation of AGL15. We compared these data to the prior microarray results to evaluate the different platforms. The new NGS data brought to light an interaction with brassinosteroid (BR) hormone signaling that was “missed” in prior Gene Ontology analysis from the microarray studies.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/plants10040758
