Salt‐stress priming enhances the tolerance of plants against subsequent exposure to a similar stress. Priming‐induced transcriptomic reprogramming is mediated by multiple epigenetic mechanisms, the best known of which is histone modifications. However, not much is known about other epigenetic responses. In this study, salt‐stress priming resulted in global DNA hypomethylation in the leaves of soybean seedlings. The DNA methyltransferase activities in primed seedlings were reduced, contributing to the overall DNA hypomethylation. Genes associated with the hypomethylated DNA regions in primed seedlings also showed a higher mean level of the active histone mark, histone 3 lysine 4 trimethylation (H3K4me3), and a lower mean level of the repressive histone mark, H3K4me2. Transcriptomic analyses supported that DNA hypomethylation played a role in fine‐tuning the chromatin status in primed seedlings to potentiate gene expressions. Motif and transcriptional network analyses revealed that DNA hypomethylation may facilitate the responses mediated by key transcription factors in the abscisic acid (ABA)‐dependent pathway. A pre‐treatment using a DNA methyltransferase inhibitor, 5‐azacytidine, could enhance salt tolerance in non‐primed soybean seedlings, similar to the priming effect, suggesting the role of DNA hypomethylation in salt‐stress priming. Overall, this research furthers our understanding of the epigenetic mechanisms involved in salt‐stress priming in soybean.

Accessible chromatin regions (ACRs) are tightly associated with gene expressions in the genome. Conserved non-coding cis-regulatory elements, such as transcription factor binding motifs, are usually found in ACRs, indicating an essential regulatory role of ACRs in the plant genome architecture. However, there have been few studies on soybean ACRs, especially those focusing on specific tissues. Hence, in this study, with the convenient ATAC-seq, we identified the ACRs in six soybean tissues, including root, leaf bud, flower, flower bud, developing seed, and pod. In total, the ACRs occupied about 3.3% of the entire soybean genome. By integrating the results from RNA-seq and transcription factor (TF) ChIP-seq, ACRs were found to be tightly associated with gene expressions and TF binding capacities in soybean. Together, these data provide a comprehensive understanding of the genomic features of ACRs in soybean. As a collection of essential genomic resources, these processed data are made available at datahub.wildsoydb.org.

Seed weight and oil/protein content are critical agronomic traits that determine soybean yield and quality. However, the key genes controlling these traits and the underlying regulatory mechanisms remain poorly understood. Here, we performed a combination of genome-wide association study and quantitative trait loci (QTL) mapping with seed weight variations, and identified a Nuclear Factor-YA (NF-YA) gene on chromosome 14 that positively regulates seed weight and protein content while negatively regulating oil content without affecting other agronomic traits, designated as Seed Weight 14 (SW14). SW14 physically interacts with GmLEC1a/b, the soybean orthologs of the central regulator of plant seed development, Leafy Cotyledon1 (LEC1), to disrupt the formation of a non-canonical NF-Y complex comprising GmLEC1, GmNF-YC2, and GmbZIP67, thereby inhibiting the GmLEC1-mediated transcriptional activation involved in seed development process. Natural allelic variations in SW14 affect the stability of the SW14 protein, which in turn confers varied seed weight and oil/protein content in soybean. Further analysis demonstrates that the elite SW14^H3 allele has undergone artificial selection during domestication and holds potential for improving yield in soybean. Collectively, our findings provide insights into the molecular basis that specifically regulates seed weight and quality, offering a potential strategy for overcoming tradeoff effects and facilitating high-yield breeding in soybean.

Transcription activation is tightly associated with the openness of chromatin and allows direct contact between transcriptional regulators and their targeted DNA for gene expression. However, there are limited studies on the annotation of open chromatin regions (OCRs) in rice (Oryza sativa), especially those in reproductive organs. Here, we characterized OCRs in rice pistils and anthers with an assay for transposase-accessible chromatin using sequencing. Despite a large overlap, we found more OCRs in pistils than in anthers. These OCRs were enriched in gene transcription start sites (TSSs) and showed tight associations with gene expression. Transcription factor (TF) binding motifs were enriched at these OCRs as validated by TF chromatin immunoprecipitation followed by sequencing. Pistil-specific OCRs provided potential regulatory networks by binding directly to the targets, indicating that pistil-specific OCRs may be indicators of cis-regulatory elements in regulating pistil development, which are absent in anthers. We also found that open chromatin of pistils and anthers responded differently to low temperature (LT). These data offer a comprehensive overview of OCRs regulating reproductive organ development and LT responses in rice.

Interactions of enhancers with promoters and transcription factors mediate chromatin loop formation to regulate downstream gene expression in response to environmental stimuli such as light.