Endosperm is a major evolutionary innovation of flowering plants, and its proper development critically impacts seed growth and viability. Epigenetic regulators have a key function in parental ...control of endosperm development. Notably, epigenetic regulation of parental genome dosage is a major determinant of seed development success, and disruption of this balance can produce inviable seed, as observed in some interploidy and interspecific crosses. These postzygotic reproduction barriers are also a potent driver of speciation. The molecular machinery and regulatory architecture governing endosperm development is proposed to have evolved under parental conflict. In this review, we emphasize parental conflict as a dialectic conflict and discuss recent findings about the epigenetic molecular machinery that mediates parental conflict in the endosperm.
Summary
Arabidopsis lamin analogs CROWDED NUCLEIs (CRWNs) are necessary to maintain nuclear structure, genome function, and proper plant growth. However, whether and how CRWNs impact reproduction and ...genome‐wide epigenetic modifications is unknown. Here, we investigate the role of CRWNs during the development of gametophytes, seeds, and endosperm, using genomic and epigenomic profiling methods.
We observed defects in crwn mutant seeds including seed abortion and reduced germination rate. Quadruple crwn null genotypes were rarely transmitted through gametophytes. Because defects in seeds often stem from abnormal endosperm development, we focused on crwn1 crwn2 (crwn1/2) endosperm. These mutant seeds exhibited enlarged chalazal endosperm cysts and increased expression of stress‐related genes and the MADS‐box transcription factor PHERES1 and its targets.
Previously, it was shown that PHERES1 expression is regulated by H3K27me3 and that CRWN1 interacts with the PRC2 interactor PWO1. Thus, we tested whether crwn1/2 alters H3K27me3 patterns. We observed a mild loss of H3K27me3 at several hundred loci, which differed between endosperm and leaves.
These data indicate that CRWNs are necessary to maintain the H3K27me3 landscape, with tissue‐specific chromatin and transcriptional consequences.
We argue that many of the crises currently afflicting science can be associated with a present failure of science to sufficiently embody its own values. Here, we propose a response beyond mere crisis ...resolution based on the observation that an ethical framework of flourishing derived from the Buddhist tradition aligns surprisingly well with the values of science itself. This alignment, we argue, suggests a recasting of science from a competitively managed activity of knowledge production to a collaboratively organized moral practice that puts kindness and sharing at its core. We end by examining how Flourishing Science could be embodied in academic practice, from individual to organizational levels, and how that could help to arrive at a flourishing of scientists and science alike.
We isolated mutations in
Arabidopsis to understand how the female gametophyte controls embryo and endosperm development. For the
DEMETER (
DME) gene, seed viability depends only on the maternal ...allele.
DME encodes a large protein with DNA glycosylase and nuclear localization domains.
DME is expressed primarily in the central cell of the female gametophyte, the progenitor of the endosperm.
DME is required for maternal allele expression of the imprinted
MEDEA (
MEA) Polycomb gene in the central cell and endosperm. Ectopic
DME expression in endosperm activates expression of the normally silenced paternal
MEA allele. In leaf, ectopic
DME expression induces
MEA and nicks the
MEA promoter. Thus, a DNA glycosylase activates maternal expression of an imprinted gene in the central cell.
Schmitz and colleagues recently investigated DNA methylation patterns in diverse flowering plant species, finding substantial variation in the extent and distribution of methylation in ...angiosperms.Please see related Research article: http://www.doi.org/10.1186/s13059-016-1059-0.
In diverse eukaryotes, epigenetic information such as DNA methylation is stably propagated over many cell divisions and generations, and can remain the same over thousands or millions of years. ...However, this stability is the product of dynamic processes that add and remove DNA methylation by specialized enzymatic pathways. The activities of these dynamic pathways must therefore be finely orchestrated in order to ensure that the DNA methylation landscape is maintained with high fidelity – a concept we term epigenetic homeostasis. In this review, we summarize recent insights into epigenetic homeostasis mechanisms in flowering plants and mammals, highlighting analogous mechanisms that have independently evolved to achieve the same goal of stabilizing the epigenetic landscape.
DNA methylation landscapes are consistently maintained by dynamic processes over evolutionary timescales.Both animals and plants possess robust positive feedback mechanisms that reinforce methylated DNA with high fidelity.Plants have evolved at least three epigenetic homeostasis mechanisms that balance robust methylation pathways, including the DNA methylation-dependent expression of the demethylase ROS1 and the DNA methylation-dependent splicing of the histone demethylase IBM1.Analogous mechanisms have likely evolved in mammals. Mutants of TET demethylases exhibit DNA hypomethylation, suggesting that the TET pathway operates as part of a feedback loop that ensures proper DNMT3 function.
The MEA Polycomb gene is imprinted in the Arabidopsis endosperm. DME DNA glycosylase activates maternal MEA allele expression in the central cell of the female gametophyte, the progenitor of the ...endosperm. Maternal mutant dme or mea alleles result in seed abortion. We identified mutations that suppress dme seed abortion and found that they reside in the MET1 methyltransferase gene, which maintains cytosine methylation. Seeds with maternal dme and met1 alleles survive, indicating that suppression occurs in the female gametophyte. Suppression requires a maternal wild-type MEA allele, suggesting that MET1 functions upstream of, or at, MEA. DME activates whereas MET1 suppresses maternal MEA::GFP allele expression in the central cell. MET1 is required for DNA methylation of three regions in the MEA promoter in seeds. Our data suggest that imprinting is controlled in the female gametophyte by antagonism between the two DNA-modifying enzymes, MET1 methyltransferase and DME DNA glycosylase.
The establishment, maintenance, and removal of epigenetic modifications provide an additional layer of regulation, beyond genetically encoded factors, by which plants can control developmental ...processes and adapt to the environment. Epigenetic inheritance, while historically referring to information not encoded in the DNA sequence that is inherited between generations, can also refer to epigenetic modifications that are maintained within an individual but are reset between generations. Both types of epigenetic inheritance occur in plants, and the functions and mechanisms distinguishing the two are of great interest to the field. Here, we discuss examples of epigenetic dynamics and maintenance during selected stages of growth and development and their functional consequences. Epigenetic states are also dynamic in response to stress, with consequences for transposable element regulation. How epigenetic resetting between generations occurs during normal development and in response to stress is an emerging area of research.
FQR1 is a novel primary auxin-response gene that codes for a flavin mononucleotide-binding flavodoxin-like quinone reductase. Accumulation of FQR1 mRNA begins within 10 min of indole-3-acetic acid ...application and reaches a maximum of approximately 10-fold induction 30 min after treatment. This increase in FQR1 mRNA abundance is not diminished by the protein synthesis inhibitor cycloheximide, demonstrating that FQR1 is a primary auxin-response gene. Sequence analysis reveals that FQR1 belongs to a family of flavin mononucleotide-binding quinone reductases. Partially purified His-tagged FQR1 isolated from Escherichia coli catalyzes the transfer of electrons from NADH and NADPH to several substrates and exhibits in vitro quinone reductase activity. Overexpression of FQR1 in plants leads to increased levels of FQR1 protein and quinone reductase activity, indicating that FQR1 functions as a quinone reductase in vivo. In mammalian systems, glutathione S-transferases and quinone reductases are classified as phase II detoxification enzymes. We hypothesize that the auxin-inducible glutathione S-transferases and quinone reductases found in plants also act as detoxification enzymes, possibly to protect against auxin-induced oxidative stress.
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