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Kohler, C.

Publications and source records attributed to Kohler, C..

4 recordsLinked to original sources

Auxin regulates endosperm cellularization in Arabidopsis

The endosperm is an ephemeral tissue that nourishes the developing embryo, similar to the placenta in mammals. In most angiosperms endosperm development starts as a syncytium, where nuclear divisions are not followed by cytokinesis. The timing of endosperm cellularization largely varies between species and the event triggering this transition remains unknown. Here we show that increased auxin biosynthesis in the endosperm prevents its cellularization, leading to seed arrest. Auxin-overproducing seeds phenocopy paternal-excess triploid seeds derived from hybridizations of diploid maternal plants with tetraploid fathers. Concurrently, auxin-related genes are strongly overexpressed in triploid seeds, correlating with increased auxin activity. Reducing auxin biosynthesis and signaling reestablishes endosperm cellularization in triploid seeds and restores their viability, highlighting a causal role of increased auxin in preventing endosperm cellularization. We propose that auxin determines the time of endosperm cellularization and thereby uncovered a central role of auxin in establishing hybridization barriers in plants.

plant biology

Paternal easiRNAs regulate parental genome dosage in Arabidopsis

The regulation of parental genome dosage is of fundamental importance in animals and plants, exemplified by X chromosome inactivation and dosage compensation. The \"triploid block\" is a classical example of dosage regulation in plants that establishes a reproductive barrier between species differing in chromosome number 1,2. This barrier acts in the endosperm, an ephemeral tissue that nurtures the developing embryo and induces the abortion of hybrid seeds through a yet unknown mechanism. Interploidy hybridizations involving diploid (2x) maternal parents and tetraploid (4x) pollen donors cause failure in endosperm cellularization, leading to embryo arrest 3. Here we show that paternal epigenetically activated small interfering RNAs (easiRNAs) are responsible for the establishment of the triploid block-associated seed abortion in Arabidopsis thaliana. Paternal loss of the plant-specific RNA polymerase IV suppressed easiRNA formation and rescued triploid seeds by restoring small RNA-directed DNA methylation at transposable elements (TEs), correlating with reduced expression of paternally expressed imprinted genes (PEGs). We propose that excess of paternally derived easiRNAs in diploid pollen prevents establishment of DNA methylation, leading to triploid seed abortion. Our data further suggest that easiRNAs form a quantitative signal for chromosome number and their balanced dosage is required for post-fertilization genome stability and seed viability.

plant biology

microRNA-triggered transposon small RNAs mediate genome dosage response

Chromosome dosage plays a significant role in reproductive isolation and speciation in both plants and animals, but underlying mechanisms are largely obscure1. Transposable elements can promote hybridity through maternal small RNA2, and have been postulated to regulate dosage response via neighboring imprinted genes3,4. Here, we show that a highly conserved microRNA in plants, miR845, targets the tRNAMet primer-binding site (PBS) of LTR-retrotransposons in Arabidopsis pollen, and triggers the accumulation of 21 to 22-nucleotide small RNA in a dose dependent fashion via RNA polymerase IV. We show that these epigenetically activated small-interfering RNAs (easiRNAs) mediate hybridization barriers between diploid seed parents and tetraploid pollen parents (\"the triploid block\"), and that natural variation for miR845 may account for \"endosperm balance\" allowing formation of triploid seeds. Targeting the PBS with small RNA is a common mechanism for transposon control in mammals and plants, and provides a uniquely sensitive means to monitor chromosome dosage and imprinting in the developing seed.

plant biology

Influence Of Desire To Belong And Feelings Of Loneliness On Emotional Prosody Perception In Schizophrenia.

Objective: Humans are social creatures, with desires to connect or belong, producing loneliness when isolated. Individuals with schizophrenia are often more isolated than healthy adults and demonstrate profound social communication impairments such as vocal affect perception (prosody). Loneliness, levels of desire for social connectedness (need to belong, NTB), and their relationship to perception of social communications have not been investigated in schizophrenia.\n\nMethod: In a sample of 69 individuals (36 SZ), we measured endorsements of loneliness and NTB, and evaluated their putative relationships to clinical symptoms and social communication abilities, as indexed by emotional prosody and pitch perception.\n\nResults: Loneliness endorsement was highly variable but particularly so in patients, whilst patients endorsed NTB at levels equivalent to healthy controls. In schizophrenia, pitch and prosody acuity were reduced, and prosody perception correlated with NTB. Loneliness, but not desire for social connectedness, correlated with negative symptoms.\n\nConclusion: Loneliness and negative symptoms likely exert bidirectional effects on each other. Loneliness and desire to form interpersonal attachments may be pivotal in shaping and stimulating social interactions and, subsequently, the ability to perceive social intent through prosody. Intact NTB levels in patients augurs well for cognitive remediation which, target vocal-communication processing to improve social skills.\n\nSignificant OutcomesO_LIPatients with schizophrenia endorsed higher levels of loneliness than controls, but ratings of desire for social connectedness were at normal levels.\nC_LIO_LIPitch acuity and prosody perception were correlated, confirming the importance of basic sensory processing in recognizing prosodic emotions.\nC_LIO_LISocio-cognitive perceptual ability (emotional prosody perception) correlated with increased desire for social connections, implying that they may still be motivated to find social interactions reinforcing. Thus interventions to improve perceptual deficits could still be an effective means of improving social function.\nC_LI\n\nLimitationsO_LICausal relationships between desire for social connections, loneliness, and emotional prosody perception cannot be inferred through correlations and cross-sectional studies alone.\nC_LIO_LISubjective endorsements of loneliness through self-report are not the same thing as objective indices of loneliness. New and more extensive tools for measuring desire for both loneliness and social connectedness may be needed.\nC_LIO_LIDirect experimental comparison of the interrelations between desire for social connectedness, loneliness, pitch acuity and emotional prosody perception in patients with schizophrenia and other populations such as autism will enable a more accurate comparison of the likely success of remediating socio-cognitive perceptual impairment in neuropsychiatric disorders.\nC_LI

neuroscience