Polycomb group (PcG) proteins play important roles in animal and plant development and stress response. Polycomb repressive complex 1 (PRC1) and PRC2 are the key epigenetic regulators of gene expression, and are involved in almost all developmental stages. PRC1 catalyzes H2A monoubiquitination resulting in transcriptional silencing or activation. The PRC1 components in the green lineage were identified and evolution and conservation was analyzed by bioinformatics techniques. RING Finger Protein 1 (RING1), B lymphoma Mo-MLV insertion region 1 homolog (BMI1), Like Heterochromatin Protein 1 (LHP1) and Embryonic Flower 1 (EMF1) are the PRC1 core components and Vernalization 1 (VRN1), VP1/ABI3-Like 1/2/3 (VAL1/2/3), Alfin-like 1–7 (AL1–7), Inhibitor of growth 1/2 (ING1/2), and Early Bolting in Short Days (EBS) / Short Life (SHL) are the associated factors. Each PRC1 subunit possesses special domain organizations, such as RING and the ring finger and WD40-associated ubiquitin-like (RAWUL) domains for RING1 and BMI1, chromatin organization modifier (CHROMO) and chromo shadow (ChSh) domains for LHP1, one or two B3 DNA binding domain(s) for VRN1, B3 and zf-CW domains for VAL1/2/3, Alfin and Plant HomeoDomain (PHD) domains for AL1–7, ING and PHD domains for ING1/2, Bromoadjacent homology (BAT) and PHD domains for EBS/SHL. Six new motifs are uncovered in EMF1. The PRC1 core components RING1 and BMI1, and the associated factors VAL1/2/3, AL1–7, ING1/2, and EBS/SHL exist from alga to higher plants, whereas LHP1 only occurs in higher plants. EMF1 and VRN1 are present only in eudicots. PRC1 components undergo duplication in the plant evolution. Most of plants carry the homologous core component LHP1, the associated factor EMF1, and several homologs in RING1, BMI1, VRN1, AL1–7, ING1/2/3, and EBS/SHL. Cabbage, cotton, poplar, orange and maize often exhibit more gene copies than other species. Domain organization analysis shows that duplicated gene functions may be of diverse. The PRC1 core components RING1 and BMI1, and the associated factors VAL1/2/3, AL1–7, ING1/2, and EBS/SHL originate from algae. The core component LHP1 is from moss and the associated factors EMF1 and VRN1 are from dicotyledon. PRC1 components are of functional redundancy and diversity in evolution.

Cold stress affects the seed germination and early growth of winter rapeseed, leading to yield losses. We employed transmission electron microscopy, physiological analyses, metabolome profiling, and transcriptome sequencing to understand the effect of cold stress (0 °C, LW) on the cotyledons of cold-tolerant (GX74) and -sensitive (XY15) rapeseeds. The mesophyll cells in cold-treated XY15 were severely damaged compared to slightly damaged cells in GX74. The fructose, glucose, malondialdehyde, and proline contents increased after cold stress in both genotypes; however, GX74 had significantly higher content than XY15. The pyruvic acid content increased after cold stress in GX74, but decreased in XY15. Metabolome analysis detected 590 compounds, of which 32 and 74 were differentially accumulated in GX74 (CK vs. cold stress) and XY15 (CK vs. cold stressed). Arachidonic acid and magnoflorine were the most up-accumulated metabolites in GX74 subjected to cold stress compared to CK. There were 461 and 1481 differentially expressed genes (DEGs) specific to XY15 and GX74 rapeseeds, respectively. Generally, the commonly expressed genes had higher expressions in GX74 compared to XY15 in CK and cold stress conditions. The expression changes in DEGs related to photosynthesis-antenna proteins, chlorophyll biosynthesis, and sugar biosynthesis-related pathways were consistent with the fructose and glucose levels in cotyledons. Compared to XY15, GX74 showed upregulation of a higher number of genes/transcripts related to arachidonic acid, pyruvic acid, arginine and proline biosynthesis, cell wall changes, reactive oxygen species scavenging, cold-responsive pathways, and phytohormone-related pathways. Taken together, our results provide a detailed overview of the cold stress responses in rapeseed cotyledons.

Plant cells’ ability to withstand abiotic stress is strongly linked to modifications in their mechanical characteristics. Nevertheless, the lack of a workable method for consistently tracking plant cells’ mechanical properties severely restricts our comprehension of the mechanical alterations in plant cells under stress. In this study, we used the Double Resonator Piezoelectric Cytometry (DRPC) method to dynamically and non-invasively track changes in the surface stress (ΔS) generated and viscoelasticity (storage modulus G′ and loss modulus G″) of protoplasts and suspension cells of rice under a drought stress of 5–25% PEG6000. The findings demonstrate that rice suspension cells and protoplasts react mechanically differently to 5–15% PEG6000 stress, implying distinct resistance mechanisms. However, neither of them can withstand 25% PEG6000 stress; they respond mechanically similarly to 25% PEG6000 stress. The results of DRPC are further corroborated by the morphological alterations of rice cells and protoplasts observed under an optical microscope. To sum up, the DRPC technique functions as a precise cellular mechanical sensor and offers novel research tools for the evaluation of plant cell adversity and differentiating between the mechanical reactions of cells and protoplasts under abiotic stress.

KNOX genes play crucial roles in cell-fate determination and body plan specification during early embryogenesis. However, the specific gene structure and functional differentiation of KNOXs in Brassica napus is still unclear. We investigated KNOX genes in Brassica rapa (B. rapa), Brassica oleracea (B. oleracea), and Brassica napus (B. napus), which are polyploidy models with genome triplication after Arabidopsis-Brassiceae divergence. In total, 15, 14, and 32 KNOX genes were identified in B. rapa, B. oleracea, and B. napus, respectively. Phylogenetic analysis classified BnKNOXs (B. napus) into three classes with conserved domain organization. Synteny analysis indicated that BnKNOXs family expansion during allopolyploidization was mainly due to whole-gene and segmental duplications. Cis-element, gene structure, and expression pattern analyses showed high conservation within the same group. RNA-seq and qRT-PCR results divided BnKNOXs into three classes with distinct expression patterns: Class I exhibited moderate and specific expression in buds and inflorescence tips; Class III showed specific low expression in seeds and stamens; while the second class showed expression in most tissues. Sub-cellular localization results showed that the three candidate genes from the three classes exhibited distinct subcellular localizations, with BnSTM-C and BnKNAT3a-A predominantly in the nucleus and BnKNATM1-A in the cytoplasm indicating different expression patterns. Collectively, these findings provide a foundation for further functional studies of BnKNOX genes in B. napus.

Rapeseed (Brassica napus L.) growth and productivity are severely constrained by drought stress worldwide. Stomata are central regulators of plant transpiration and gas exchange, and therefore, represent key targets for enhancing water-use efficiency and drought tolerance. The transcription factor ABSCISIC ACID INSENSITIVE 4 (ABI4), a key regulator of the abscisic acid (ABA) signaling pathway, plays crucial roles in plant abiotic stress responses and stomatal regulation. Nevertheless, the biological functions of BnaABI4 in B. napus remain largely unclear. In this study, four BnaABI4 paralogs were identified in the elite rapeseed cultivar ZS11 through genome-wide identification and comprehensive bioinformatic analyses. Each BnaABI4 protein harbors only one conserved AP2 domain, and their promoters contain multiple stress/hormone-responsive cis-regulatory elements (CREs). We subsequently generated BnaABI4-4 overexpression (OE) lines as well as BnaABI4 CRISPR/Cas9-mediated knockout (KO) transgenic lines. Phenotypic assays demonstrated that OE line had reduced transpiration rate (Tr), stomatal conductance (Gs) and stomatal density, along with enhanced drought tolerance, whereas KO lines showed the opposite phenotype. Transcriptome profiling identified numerous differentially expressed genes (DEGs) enriched in biological pathways associated with stomatal regulation, ABA signal transduction, and drought acclimation. Further Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses confirmed significant enrichment of DEGs in processes including stomatal development, stomatal movement, reactive oxygen species (ROS) homeostasis, and drought tolerance. Collectively, our findings demonstrate that BnaABI4 negatively regulates stomatal density while positively contributing to drought tolerance in B. napus. This study lays a mechanistic foundation for genetic improvement and molecular breeding of drought-tolerant rapeseed cultivars.

Soil salinity is a major abiotic stressor that constrains plant growth and development, yet the coordinated regulatory mechanisms underlying salt stress impacts on plant cell mechanical properties and the cytoskeleton remain elusive. In this study, tobacco suspension cells were employed as a model system. Combining mechanical measurements, fluorescence microscopy imaging, and bright-field morphological observation, we systematically characterized the dynamic response patterns of cell-generated surface stress (ΔS), cell viscoelastic index (CVI), microfilament cytoskeleton structure, as well as cell morphology and plasmolysis under NaCl stress ranging from 50 to 150 mmol/L. The results revealed three distinct response thresholds: 50 mmol/L NaCl treatment induced only transient ΔS fluctuations and mild plasmolysis, with no significant changes in CVI or microfilament fluorescence intensity, suggesting a safe tolerance threshold. The 75–100 mmol/L NaCl treatments triggered reversible “rise–recovery” mechanical responses in ΔS and CVI. The microfilament cytoskeleton showed minor structural adjustments, and plasmolysis increased gradually but remained reversible, defining this range as a reversible acclimation phase. The 125–150 mmol/L NaCl treatment caused an irreversible decline in ΔS (with a sharp instantaneous drop at 150 mmol/L). CVI variations diminished and stabilized after 6 h. The microfilament cytoskeleton suffered progressive disruption, as fluorescence intensity dropped to 1% of the control group at 150 mmol/L, accompanied by severe plasmolysis and protoplast shrinkage, indicating irreversible cellular damage. These findings demonstrate a concentration-dependent gradient effect of NaCl stress, highlighting tight coordination between mechanical properties, cytoskeletal integrity, and morphological adaptation. This work provides critical cytological insights into the molecular regulation of plant salt stress responses.