Tianxu Zhang

Transgenerational epigenetic inheritance (TEI) enables plants to transmit adaptive chromatin states across generations. However, the mechanisms by which these states are maintained and stabilised during TEI remain unclear. Here, we investigate the TEI of repressive marks (H3K27me3 and DNA methylation) together with the active mark H3K4me3, which are associated with distinct reinforcement mechanisms, using reciprocal crosses of Arabidopsis ecotypes Col‐0 and C24. We show that all three marks undergo TEI but exhibit distinct inheritance patterns depending on their reinforcement mechanisms. These inheritance patterns are modulated by DDM1, which coordinates the propagation of repressive chromatin states. Our results indicate that chromatin remodelling, through its effects on nucleosome organisation and histone variant dynamics, plays a key role in shaping TEI via chromatin context in plants.

Although chromatin states are closely associated with epigenetic modifications, how they influence each other remains to be fully elucidated. In this study, we found that mutation of DECREASED IN DNA METHYLATION 1 (DDM1) in soybean leads to genome-wide chromatin homogenization, characterized by a loosening of heterochromatin and a tightening of euchromatin. This remodeling triggers 2 distinct molecular pathways: in heterochromatin, increased release of small RNAs activates the noncanonical RdDM pathway; while in euchromatin, transposable elements (TEs) are enriched with H3K9me2 modifications, which in turn activate the CMT2 pathway. Together, these pathways drive a pronounced burst of CHH methylation at the whole genome level. This epigenetic remodeling correlates with massive transcriptional dysregulation, upregulating stress responses and downregulating photosynthesis, linking local H3K9me2 changes on TEs, ultimately leading to severe phenotypes. Our findings reveal a unique, bidirectional pathway for CHH regulation in plants with complex chromatin states remodeling.

The AT-hook motif nuclear localized (AHL) gene family encodes transcription factors pivotal in regulating plant growth, development, and responses to abiotic stimuli, including low temperature, salinity, darkness, and drought. In this study, we systematically identified 21 BpAHL genes in birch and characterized their sequence features, evolutionary relationships, and expression dynamics. Phylogenetic analysis classified BpAHLs into two clades (Clade-A and Clade-B) and three types (Type-I, -II, and -III), based on PPC domain and AT-hook motifs. Chromosomal mapping revealed an even distribution across nine chromosomes and one contig, with dispersed duplication events recognized as the major driver of BpAHL family expansion. Tissue-specific expression profiling uncovered striking divergence: Type-I BpAHLs displayed root-predominant expression, whereas Type-II/III BpAHLs were highly expressed in plant flowers and leaves. Notably, Type-II/III BpAHL genes in leaves showed distinct expression patterns in response to cold and heat stresses, while Type-I BpAHLs in roots were down-regulated under salt stress. This study provides a comprehensive phylogenomic and functional analysis of the AHLs in birch, providing insights into their roles in enhancing abiotic stress resilience in forest trees.

As essential organs of reproduction in angiosperms, flowers, and the genetic mechanisms of their development have been well characterized in many plant species but not in the woody tree yellowhorn (Xanthoceras sorbifolium). Here, we focused on the double flower phenotype in yellowhorn, which has high ornamental value. We found a candidate C-class gene, AGAMOUS1 (XsAG1), through Bulked Segregant Analysis (BSA) sequencing and genetics analysis with a Long Interpersed Nuclear Elements 1 (LINE1) transposable element fragment (Xsag1-LINE1-1) inserted into its second intron that caused a loss-of-C-function and therefore the double flower phenotype. In situ hybridization of XsAG1 and analysis of the expression levels of other ABC genes were used to identify differences between single- and double-flower development processes. These findings enrich our understanding of double flower formation in yellowhorn and provide evidence that transposon insertions into genes can reshape plant traits in forest trees.

CRISPR/dCas9 is an important DNA modification tool in which a disarmed Cas9 protein with no nuclease activity is fused with a specific DNA modifying enzyme. A previous study reported that overexpression of the TET1 catalytic domain (TET1cd) reduces genome-wide methylation in Arabidopsis. A spontaneous naturally occurring methylation region (NMR19-4) was identified in the promoter region of the PPH (Pheophytin Pheophorbide Hydrolase) gene, which encodes an enzyme that can degrade chlorophyll and accelerate leaf senescence. The methylation status of NMR19-4 is associated with PPH expression and leaf senescence in Arabidopsis natural accessions. In this study, we show that the CRISPR/dCas9-TET1cd system can be used to target the methylation of hypermethylated NMR19-4 region to reduce the level of methylation, thereby increasing the expression of PPH and accelerating leaf senescence. Furthermore, hybridization between transgenic demethylated plants and hypermethylated ecotypes showed that the demethylation status of edited NMR19-4, along with the enhanced PPH expression and accelerated leaf senescence, showed Mendelian inheritance in F1 and F2 progeny, indicating that spontaneous epialleles are stably transmitted trans-generationally after demethylation editing. Our results provide a rational approach for future editing of spontaneously mutated epialleles and provide insights into the epigenetic mechanisms that control plant leaf senescence.

Abscisic acid (ABA) plays a crucial role in various aspects of plant growth and development, including fruit development and ripening, seed dormancy, and involvement in response to various environmental stresses. In almost all higher plants, ABA signal transduction requires three core components; namely, PYR/PYL/RCAR ABA receptors (PYLs), type 2C protein phosphatases (PP2Cs), and class III SNF-1-related protein kinase 2 (SnRK2s). The exploration of these three core components is not comprehensive in soybean. This study identified the GmPYL-PP2C-SnRK2s gene family members by using the JGI Phytozome and NCBI database. The gene family composition, conservation, gene structure, evolutionary relationship, cis-acting elements of promoter regions, and its coding protein domains were analyzed. In the entire genome of the soybean, there are 21 PYLs, 36 PP2Cs, and 21 SnRK2s genes; further, by phylogenetic and conservation analysis, 21 PYLs genes are classified into 3 groups, 36 PP2Cs genes are classified into seven groups, and 21 SnRK2s genes are classified into 3 groups. The conserved motifs and domain analysis showed that all the GmPYLs gene family members contain START-like domains, the GmPP2Cs gene family contains PP2Cc domains, and the GmSnRK2s gene family contains S_TK domains, respectively. Furthermore, based on the high-throughput transcriptome sequencing data, the results showed differences in the expression patterns of GmPYL-PP2C-SnRK2s gene families in different tissue parts of the same variety, and the same tissue part of different varieties. Our study provides a basis for further elucidation of the identification of GmPYL-PP2C-SnRK2s gene family members and analysis of their evolution and expression patterns, which helps to understand the molecular mechanism of soybean response to abiotic stress. In addition, this provides a conceptual basis for future studies of the soybean ABA core signal pathway.