Poly (vinyl alcohol) with pendent styrylpyridinium groups (SbQ) is insolubilized by photoirradiation. An association takes place in SbQ groups. The association of polymer chains becomes marked with increasing the number of SbQ groups. Mainly intermolecular crosslinks were formed. Transparent and homogeneous macrogels consisting of several intermolecular crosslinks are obtained.The proportion of the free water to the bound water in PVA-SbQ gels was 3.3-2.9 despite of the large change in conversion of photodimerization of SbQ groups, x=0.27-0.58. The water uptake after swelling of the gels in water increased 6-27 times compared to the original weight at pH=7. The higher the degree of photocrosslinking, the lower was the degree of swelling. The water diffusion coefficients, D , were (2.2-5.8)xlO-~cm2s-~ for a 88% saponified PVA with 1.3 mol% SbQ groups. The volume of the gel increased discontinuously about 10-fold for the 99% saponified PVA with 0.096 mol% SbQ and 51% water (49% acetone). The acetone concentration at the transition decreased with increasing the degree of saponification of the PVA.-Poster presented at the "
The MADS domain transcription factor AGAMOUS (AG) regulates floral meristem termination by preventing maintenance of the histone modification H3K27me3 along the KNUCKLES (KNU) coding sequence. At two days after AG binding, cell division has diluted the repressive mark H3K27me3, allowing activation of KNU transcription prior to floral meristem termination. However, how many other downstream genes are temporally regulated by this intrinsic epigenetic timer and what their functions are remain unknown. Here, we identify direct AG targets regulated through cell cycle–coupled H3K27me3 dilution in Arabidopsis thaliana. Expression of the targets KNU, AT HOOK MOTIF NUCLEAR LOCALIZED PROTEIN18 (AHL18), and PLATZ10 occurred later in plants with longer H3K27me3-marked regions. We established a mathematical model to predict timing of gene expression and manipulated temporal gene expression using the H3K27me3-marked del region from the KNU coding sequence. Increasing the number of del copies delayed and reduced KNU expression in a Polycomb Repressive Complex 2– and cell cycle–dependent manner. Furthermore, AHL18 was specifically expressed in stamens and caused developmental defects when mis-expressed. Finally, AHL18 bound to genes important for stamen growth. Our results suggest that AG controls the timing of expression of various target genes via cell cycle–coupled dilution of H3K27me3 for proper floral meristem termination and stamen development.
In angiosperms, transition from floral organ maintenance to abscission determines plant reproductive success and seed dispersion. For petal abscission, local cell fate decision at petal cell base is more important than general senescence or cell death of petals at organ levels. However, how this decision is regulated in a spatiotemporal manner remains unclear. Here, we describe a jasmonic acid (JA)–regulated chromatin state change that directs the local cell fate determination via autophagy at the base of petals. During petal maintenance phase, transcriptional co-repressors of JA signaling accumulate at the base of petals to block MYC activity, leading to lower reactive oxygen species (ROS) levels. JA acts as an airborne signaling molecule transmitted from stamens to petals and accumulates primarily in petal bases to trigger epigenetic reprograming, allowing MYC transcription factors to interact with MEDIATOR25 and to increase chromatin accessibility for key downstream targets, such as Arabidopsis NAC DOMAIN-CONTAINING PROTEIN102 (ANAC102). ANAC102 specifically accumulates at the base of petals just prior to petal abscission and triggers local ROS accumulation and cell death via AUTOPHAGY-RELATED GENES induction. Notably, this ANAC102-triggered autophagy at the petal base causes maturation, vacuolar delivery, and breakdown of autophagosome for terminal cell differentiation. Because dynamic changes in the number of vesicles and cytoplasmic components in the vacuole are often seen in many plants, the local cell fate determination by autophagy may be conserved for petal abscission across angiosperms and may have been recruited under the JA/NAC module to pattern plant organ detachment systems.
The termination of floral meristems is regulated by the MADS domain transcription factor AGAMOUS (AG) by passively diluting the H3K27me3 mark along the KNUCKLES (KNU) coding sequence. How many other downstream genes are similarly regulated by this intrinsic epigenetic timer and whether it can be harnessed for engineering synthetic circuits are unknown. Here, we describe a biotimer gene regulatory network downstream of AG and manipulate the timing of KNU expression through a synthetic system. We manipulated temporal gene expression using the del region from the KNU coding sequence, which is decorated by H3K27me3-marked nucleosomes. Increasing the number of del copies delayed and reduced KNU expression in a PRC2- and cell cycle-dependent manner. We propose that PRC2 deposits H3K27me3, while cell divisions dilute H3K27me3 accumulation on the extended KNU coding sequence. Our results shed light on temporal transitions governing flower development and provide a novel tool for tunable gene expression.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.