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Sex-specific ethylene responses drive floral sexual plasticity in Cannabis sativa.

Cannabis sativa L. exhibits pronounced sexual plasticity in which both XX and XY plants can undergo floral phenotypic sex reversal in response to ethylene modulation, yet the underlying molecular mechanisms remain poorly defined. Here, we present the most extensive multi-omic analysis of ethylene-induced sex change in C. sativa to date, integrating over 130 RNA-seq libraries, ethylene pathway metabolite quantification, and whole-genome sequencing across three XX and XY genotypes. Treatments with silver thiosulfate and ethephon induced more than 80% phenotypic conversion, but transcriptomic responses diverged sharply between XX and XY plants. Profiling 47 ERGs revealed 14 high-confidence candidates, including CsACS1, CsACO5, CsERF1, and CsMTN, with sex-specific and temporal expression patterns that show dynamic ethylene mediation of plasticity. Early transcriptional activation occurred prior to the emergence of flowers, within 18 h of sex-change treatments and the photoperiod-induced transition to flowering. As opposite-sex floral tissues emerged, ethylene-related gene expression shifted accordingly within developing floral organs, with distinct sets of genes stabilizing the opposite-sex phenotype in XX and XY plants. Several candidates were located in non-recombining regions of the X chromosome or were absent from the Y chromosome, and most exhibited low nucleotide diversity, consistent with functional constraint. These results provide a high-resolution view of ethylene-responsive sexual plasticity in cannabis and show that the shared capacity for sex reversal in XX and XY plants is implemented through distinct regulatory trajectories that produce opposite-sex floral phenotypes. This work expands the mechanistic understanding of sex expression in dioecious species and identifies candidate genes relevant to the development of sex-stable cultivars.

Ethylenes

Ethylene signaling negatively regulates rapeseed resistance to Plasmodiophora brassicae.

Clubroot, caused by Plasmodiophora brassicae, poses a serious threat to the rapeseed (Brassica napus) industry. Due to B. napus being an allopolyploid with a complex genome and the current scarcity of available resistance gene resources, the molecular basis of rapeseed resistance to P. brassicae remains poorly understood. Here, we performed a functional characterization of BnEIN2 (ethylene-insensitive protein) to explore the role of ethylene signaling in rapeseed resistance to P. brassicae. The Bnein2 mutants generated through CRISPR/Cas9 technology exhibited enhanced resistance to P. brassicae, along with reduced 1-aminocyclopropane-1-carboxylic acid (ACC)/S-adenosyl-L-methionine (SAM) accumulation and ethylene insensitivity. Pharmacological assays demonstrated that inhibitors of ethylene biosynthesis or signaling improved the resistance of Bnein2 mutant plants to P. brassicae. Transcriptome analysis revealed that loss-of-function of BnEIN2 affected the expression of ethylene-, auxin-, and cytokinin-related genes. Moreover, the increased resistance of Bnein2 mutants to P. brassicae was accompanied by a reduction in auxin (indole-3-acetic acid, IAA) biosynthesis and degradation of cytokinin (trans-zeatin, TZ). Collectively, these findings establish the negative regulatory role of ethylene signaling in rapeseed resistance to P. brassicae. This study represents the first effort to elucidate rapeseed resistance to P. brassicae by directly obtaining rapeseed genetic material and offer novel insights into the hormonal regulatory network underlying disease resistance and valuable resources for breeding clubroot-resistant varieties.

BnEIN2

The H3K27me3 reader GmLHP1 impairs Phytophthora sojae resistance by repressing ethylene precursor accumulation in soybean.

Phytophthora root rot, caused by Phytophthora sojae, is a devastating soilborne disease of soybean (Glycine max). However, the epigenetic regulation of soybean responses to P. sojae remains incompletely understood. Here, using genetic, molecular and biochemical approaches, we characterized the functions of LIKE HETEROCHROMATIN PROTEIN 1 (GmLHP1) and its downstream regulatory network. We demonstrated that GmLHP1, as a reader of H3K27me3, negatively regulates soybean resistance to P. sojae. GmLHP1 binds to H3K27me3 peptides in vitro and colocalizes with H3K27me3 marks genome-wide in vivo. The integrated chromatin immunoprecipitation sequencing and RNA sequencing analysis identified the ethylene biosynthesis pathway gene 1-AMINO-CYCLOPROPANE-1-CARBOXYLATE SYNTHASE 18 (GmACS18) as being enriched for H3K27me3 and bound by GmLHP1, leading to its transcriptional downregulation. Notably, GmLHP1 associates with the GmACS18 promoter by directly binding to AATTAA motifs and recognizing H3K27me3 marks. Moreover, GmACS18 enhances defense against P. sojae by accumulating the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC). Further analysis unveiled that recognition of H3K27me3 by GmLHP1 is essential for regulating soybean resistance to P. sojae through repressing GmACS18 transcription and decreasing ACC accumulation. Our findings reveal a novel epigenetic regulatory mechanism in which the H3K27me3 reader GmLHP1 blocks soybean resistance to P. sojae by repressing ethylene precursor ACC accumulation.

ACC accumulation

Rice ETHYLENE RESPONSE FACTOR 101 increases leaf angle by upregulating BRASSINOSTEROID UPREGULATED 1.

The leaf angle (LA) is a critical component of plant architecture that directly influences photosynthetic efficiency and grain yield. In the present study, we found that ETHYLENE RESPONSE FACTOR 101 (OsERF101), an APETALA2/ethylene response factor, plays a role in LA formation. A null mutation in OsERF101 resulted in reduced LA, whereas transgenic plants overexpressing OsERF101 (OsERF101-OEs) exhibited increased LA. OsERF101 increased the development of the adaxial lamina joint (LJ). Transactivation assays and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis indicated that OsERF101 activated BRASSINOSTEROID UPREGULATED 1 (OsBU1) transcription by directly binding to its promoter. However, OsERF101 expression was suppressed by exogenous brassinosteroid (BR) treatment and elevated endogenous brassinolide (BL) levels during LJ development. Additionally, OsERF101 downregulated the expression of BR biosynthesis genes, including Brassinosteroid-deficient dwarf2 (OsBRD2) and CYP90B2/OsDWARF4, leading to reduced levels of endogenous BL, the most active BR, in OsERF101-OEs. These findings suggested that OsERF101 mediates a negative feedback loop that balances endogenous BR levels and signaling. Collectively, rice plants have evolved diverse regulatory mechanisms involving OsERF101 to tune LA formation and optimize plant architecture finely.

Oryza

Ethylene response factors ERF.B2 and ERF.B5 synergically regulate ascorbic acid biosynthesis at multiple sites in tomato.

Ascorbic acid (AsA) is an important growth regulator and antioxidant in plants. It is acknowledged as a quality indicator in tomato (Solanum lycopersicum). Although the AsA biosynthetic pathway has been elucidated, its regulatory mechanisms remain largely unknown. In the present study, two members of the ethylene response factor (ERF) family, SlERF.B2 and SlERF.B5, were found to be co-expressed with SlGGP1, a pivotal gene in AsA biosynthesis. These two transcription factors were biochemically confirmed to bind to the DRE motif (GCCGAC/GTCGGC) of the SlGGP1 promoter. Notably, the SlERF.B2 and SlERF.B5 functioned as a dimer to regulate SlGGP1 expression and AsA biosynthesis. Overexpression of SlERF.B2 and SlERF.B5 enhanced the AsA levels up to 149 and 140%, respectively, whereas knockout of either of them could significantly decrease the AsA levels by up to 27%. DNA affinity purification sequencing (DAP-seq) indicated that SlERF.B2 synergistically regulates AsA biosynthesis at multiple sites by targeting the promoters of SlGPI and SlDHAR1. Overexpression of SlERF.B2 or SlERF.B5 in tomato conferred a high capacity for scavenging reactive oxygen species and enhanced tolerance to oxidation and salt stress, potentially by elevating the AsA content. This study unravels novel regulators of AsA biosynthesis and elucidates a molecular network that should facilitate the improvement of this nutrient in tomato and enhance stress tolerance in plants.

Solanum lycopersicum

A Rapid Poly(ethylene glycol)-Assisted Magnetic Isolation Approach for High-Throughput Extracellular Vesicle Isolation and Subsequent Biomarker Analysis.

Extracellular vesicles (EVs) are crucial mediators of intercellular communication and have the potential to serve as biomarkers for disease diagnosis and therapeutic monitoring. However, most EV isolation methods often require large sample volumes and specialized instruments or involve trade-offs between purity, yield, cost, and scalability. We developed MagPEG, a workflow that combines poly(ethylene glycol) (PEG)-mediated EV aggregation with magnetic beads to provide a simple, reproducible alternative to ultracentrifugation, size-exclusion chromatography, and commercial precipitation kits. Our optimization experiments clarified the PEG concentration, ionic strength, and bead surface chemistry that collectively influence EV aggregation, capture efficiency, and contaminant coprecipitation, allowing us to define conditions that improve purity while maintaining high recovery. Compared with commonly used methods, MagPEG produced EVs with comparable size distribution, EV markers, and proteomic profiles while relying only on standard laboratory supplies. A key feature of the platform is that EVs and EV-associated DNA, RNA, and proteins can be sequentially extracted from the same bead-bound material, reducing sample loss and hands-on time and enabling multiomic analysis for limited clinical or small animal samples. MagPEG is compatible with downstream applications including proteomics, bead-based assays, and miRNA quantification. When applied to human serum, the method supported high-throughput EV proteomic profiling and enabled the identification of Alzheimer's disease-associated protein signatures, illustrating its utility for biomarker discovery. Overall, our results establish MagPEG as a powerful, rapid, scalable, and high-throughput solution for translational applications in biomarker discovery.

Polyethylene Glycols

A SlEIN2-centered epigenetic network equilibrates fruit ripening and innate immunity in tomato.

Ethylene and DNA/RNA methylation serve as essential factors in controlling fruit ripening. In tomato, the mRNA N6-methyladenosine (m6A) demethylase SlALKBH2 regulates mRNA stability of the DNA 5-methylcytosine demethylase gene SlDML2 via modulating m6A modifications. However, the interplay between ethylene and these epigenetic marks remains unclear. Here, we show that SlDML2 expression is significantly inhibited in slein2 fruits, but remains unchanged in the high-order sleil mutant (sleil1 sleil2 sleil3/SlEIL3 sleil4 and sleil1 sleil2/SlEIL2 sleil3 sleil4) fruits, indicative of post-transcriptional regulation of SlDML2 expression by SlEIN2, a core ethylene signaling component acting upstream of the master transcription factors SlEILs. Interestingly, SlEIN2 preferentially regulates the asymmetric CHH methylation in promoters of several key ripening regulator genes. Mechanistically, SlEIN2 physically interacts with SlALKBH2, which promotes SlDML2 expression in a SlEIN2-dependent manner. Furthermore, SlAGO4A and SlAGO4B, components of the RNA-directed DNA methylation pathway, were upregulated in slein2 fruits. Silencing SlAGO4A/B in wild-type fruit caused precocious ripening with necrosis, indicative of hyperimmunity. Conversely, SlAGO4A/B silencing in slein2 markedly delayed this hyperimmunity. Taken together, our study reveals that ethylene, beyond transcriptional regulation, employs an elaborate epigenetic machinery mediated by the SlAGO4A/B-SlEIN2-SlALKBH2 module to balance fruit ripening and innate immunity.

Solanum lycopersicum

Genome-wide screening and functional analysis of protein glycosylation-related genes involved in tomato fruit ripening.

Protein glycosylation, an essential co- and post-translational modification, plays critical roles in plant growth, development, and stress responses. However, its functional role in tomato fruit ripening has not been extensively investigated. Here, key protein glycosylation-related genes involved in tomato fruit ripening were identified by genome-wide screen and subsequently functional characterization. First, a dataset comprising 242 glycosylation-related proteins was established based on Gene Ontology annotations in tomato, combined with sequence homology to protein glycosylation-related proteins from Arabidopsis thaliana and Homo sapiens. Then, Subsequently, 28 genes encoding highly expressed glycosylation-related proteins (RPKM > 30) at the breaker (BR) stage were selected for functional screening, and subsequently 6 genes were identified as regulators of fruit ripening by method of virus-induced gene silencing (VIGS). Among them, Solyc03g098600 (STT3B), Solyc01g109410 (OST48), Solyc04g082670 (RPN1), and Solyc08g076460 (DAD1) functioned as positive regulators of tomato fruit ripening, whereas Solyc04g005340 (UAM2) and Solyc08g075340 (XEG113), acted as negative regulators. The expression of these genes responded dynamically to multiple ripening-related cues, including temperature, light, ethylene, and transcription factors. Furthermore, silencing of these genes individually affected the expression of genes involved in fruit ripening, including ethylene biosynthesis genes (ACS2, ACS4, ACO1, and ACO3), ripening-associated transcription factors (RIN, NOR, NOR-LIKE1, FUL1, and FUL2), and the key gene (PSY1) of lycopene biosynthesis pathway. Collectively, these findings demonstrate that protein glycosylation plays an important role in tomato fruit ripening by modulating ethylene signaling, ripening-associated transcriptional regulation, and lycopene biosynthesis.

Fruit ripening

Genome-wide identification and characterization of 1-amino-cyclopropane-1- carboxylate synthase (ACS) gene family in Carica papaya and expression insights in response to hormone stress.

ACC-synthase (1-aminocyclopropane-1-carboxylate synthase), also known as the ACS gene, plays a pivotal role in ethylene production, which is of great importance in the fruit ripening process for producing saleable yield (marketable fruit). The ACS gene family presumably controls stress responses, plant growth and development, and particularly fruit ripening. Computational biology was used as an essential tool to identify seven ACS genes in Carica papaya (red hermaphrodite) using an RNA-seq database (NCBI GEO). Further, the phylogenetic relationships of ACS genes determined gene family resemblance in the genomes of Hordeum vulgare, Musa acuminata, C. papaya, and Arabidopsis thaliana; therefore, the identified gene families were further classified into four distinct clades (Type-I, Type-II, Type-III, and Type-IV) in alignment with the well-established Arabidopsis classification. Moreover, encompassing gene structure, domain motifs, cis-element phylogenetic profiling, synteny, and transcriptomic profiling unveiled latent structural and functional attributes within CpACS genes. Through segmental duplication of CpACS, insights into evolutionary duplication events were predicted. The paralogous behavior of ACS genes in C. papaya and a comprehensive transcriptomic analysis demonstrated both up- and down-regulation patterns in response to ethylene treatment at different time points during the fruit ripening process, using the papaya manual handbook V2 (2021). Gene expression showed upregulation of two essential CpACS genes, CpACS5 and CpACS6. RT-qPCR validates the expression of these important genes during fruit ripening. However, one gene, CpACS7, is expressed in the later stages of fruit development. Our results demonstrated novel avenues for understanding the expression pathways of the ACS gene family in red hermaphrodite papaya, and most of these genes were linked to regulating various abiotic stresses, plant growth, and fruit development.

Carica

The transcription factor PavERF28 promotes fruit softening by regulating cell wall degradation in sweet cherry (Prunus avium L.).

Fruit softening is a critical determinant of shelf life and marketability in sweet cherry (Prunus avium L.). This process is predominantly driven by cell wall disassembly, which is tightly regulated by transcription factors. Despite evidence for ethylene's role in sweet cherry softening, how these signals are transduced to regulate the expression of cell wall-modifying genes is unclear. Here, we identified the ethylene-responsive transcription factor PavERF28 as a key regulator in this process. Overexpression of PavERF28 significantly upregulated the transcriptional levels of genes involved in pectin degradation (including genes encoding polygalacturonase, pectin methylesterase inhibitor, and pectate lyase), thus effectively enhancing fruit softening. Moreover, heterologous overexpression of PavERF28 in tomato confirmed its function in promoting fruit softening. At the molecular level, PavERF28 was shown to directly activate the expression of two polygalacturonase genes (PavPG1 and PavPL5) by binding to their promoters, which catalyze pectin depolymerization and thus drive softening. Collectively, our work provides an in-depth elucidation of the regulatory mechanism by which ERF family members control fruit softening in sweet cherry and offers potential targets for the manipulation of fruit ripening, especially softening.

Cell Wall

Transcriptional and phytohormonal regulation of positional ear development reveals yield strategies in maize.

Maize (Zea mays L.) is a vital global crop, contributing ∼37% of annual grain production. Enhancing yield per unit area is crucial for food security, yet research has primarily focused on single-ear traits, overlooking the regulation of double ears-a key determinant of prolificacy. While secondary ears drive yield variability under prolificacy-favoring conditions, the mechanisms governing ear formation across shoot positions remain poorly understood. Here, we performed high-resolution transcriptomic analysis of 66 samples from three ear types (primary, secondary and third) in maize inbred B73. We uncovered distinct hormonal developmental dynamics: strigolactone (SL) signaling genes, particularly SBP transcription factors, dominated in primary (I) ears, whereas ethylene-related genes (e.g., ZmEREB131, ZmACCO35) were enriched in third (III) ears. Functional validation confirmed that knockout of ZmEREB131 and ZmACCO35 accelerated development and elongated ears compared to wild-type, implicating ethylene (ETH) signaling in ear maturation arrest. Notably, SL inhibitor application synchronized primary and secondary ear development, boosting total yield by >20% without compromising primary ear performance. Our study elucidates the transcriptional networks underlying differential ear development and provides actionable strategies for yield improvement through targeted hormonal modulation. These findings advance the understanding of maize inflorescence biology and offer molecular tools for breeding high-yielding varieties.

RNA-seq

Time-course transcriptome and proteomic dynamics during the de novo shoot organogenesis in Chinese fir (Cunninghamia lanceolata).

De novo shoot organogenesis (DNSO) enables plants to regenerate shoots from various explants, offering valuable opportunities for research and plant biotechnology applications. While significant progress has been made in understanding regeneration in angiosperms, the regulatory mechanisms in gymnosperms, particularly Chinese fir (Cunninghamia lanceolata), remain poorly understood, despite its importance as a key timber species in China. This study successfully established an efficient DNSO protocol for Chinese fir, identifying six distinct stages in the process through cellular-level analysis. Time-course transcriptome and proteomics analyses revealed dynamic changes in mRNA and protein levels during regeneration. Notably, proteins showed more significant alterations across a broad range of biological processes, often independent of corresponding mRNA changes. Key pathways associated with ethylene metabolism and abiotic stress responses were enriched, highlighting their critical roles in regeneration. Further experiments confirmed that moderate osmotic stress treatments (150 mm mannitol) and ethylene treatment (100 μm ACC and 5 μm AgNO3) substantially enhanced DNSO efficiency. In summary, this study uncovers the molecular mechanisms underlying Chinese fir DNSO, providing valuable insights into improving plant regeneration efficiency in this economically important species. These findings contribute to advancements in plant biotechnology and sustainable forestry practices.

Cunninghamia

CRISPR/Cas9-Mediated Mutagenesis of OsERF94 Enhances Pre-Harvest Sprouting in Rice.

Pre-harvest sprouting (PHS), where seeds germinate on panicles before harvest under humid conditions, is a serious global issue in cereal crop production, including rice. Fine-mapping of the previously reported chromosome 4 locus identified OsERF94 as a strong candidate gene for functional validation. In this study, we investigated the role of OsERF94 in PHS using CRISPR/Cas9 gene editing. The CRISPR/Cas9-mediated mutagenesis of OsERF94 induced frameshift mutations, resulting in a loss-of-function of OsERF94 in the 1-I-ET and 2-D-ET lines. The 1-I-ET and 2-D-ET lines exhibited significantly higher germination rates under PHS conditions compared to the wild type, indicating increased susceptibility to PHS. Whole-genome re-sequencing confirmed that few or no mutations could be detected at off-target candidate sites in both edited lines, ensuring the precision of the CRISPR/Cas9 gene editing. A transcriptome analysis revealed altered expression patterns of several GA-related genes, including OsLOL1, OsKO3, OsGA3ox2, and OsGA2ox5 in the OsERF94 mutant lines. The up-regulation of GA biosynthetic genes and the down-regulation of GA deactivation genes observed in both the OsERF94 mutant lines suggest possible alterations in GA metabolism during the early stages of PHS. Transient luciferase reporter assays using a single-luciferase system suggested that OsERF94 may be associated with changes in the promoter activities of several GA- and ethylene-related genes. These findings suggest that OsERF94 may contribute to the regulation of PHS, potentially through moderation of GA- and ethylene-related pathways. Overall, this study improves our understanding of the molecular role of OsERF94 in PHS and highlights its potential as a target for the genetic improvement of PHS resistance in rice-breeding programs.

OsERF94

Genome-wide AP2/ERF analysis identifies HmaERF87 as a positive regulator of Hydrangea macrophylla leaf spot resistance.

A total of 164 APETALA2/ethylene-responsive factor (AP2/ERF) genes were identified in Hydrangea macrophylla, and HmaERF87 positively contributes to leaf spot resistance. The APETALA2/ethylene-responsive factor (AP2/ERF) transcription factor family plays important roles in plant stress responses, but its contribution to disease resistance in Hydrangea macrophylla (hydrangea) remains poorly understood. In this study, 164 AP2/ERF genes were identified in the H. macrophylla genome and classified into APETALA2 (AP2), ethylene-responsive factor (ERF), dehydration-responsive element-binding (DREB), and related to ABI3/VP1 (RAV) subfamilies. Their chromosomal distribution, conserved motifs, gene structures, and duplication patterns were analyzed. A total of 46 pathogen-responsive H. macrophylla AP2/ERF (HmaERF) genes were identified from the RNA sequencing (RNA-seq) dataset of resistant and susceptible cultivar leaves collected before and after Corynespora cassiicola inoculation. Promoter analysis revealed that the HmaERF genes with upregulated expression post-C. cassiicola infection showed a higher frequency and copy number of jasmonate-responsive cis-regulatory elements, suggesting their possible involvement in hormone-mediated defense responses. Three infection-induced candidate genes, including HmaERF56, HmaERF87, and HmaERF129, were selected for functional validation using virus-induced gene silencing (VIGS) in hydrangea leaf discs. Silencing of HmaERF87 expression via VIGS significantly increased lesion development after C. cassiicola inoculation, whereas the transient overexpression of HmaERF87 reduced the area of leaf disc lesions. Subcellular localization showed that the HmaERF87 protein was localized in the nucleus, and yeast assays indicated that its transcriptional activation activity was mainly associated with the C-terminal region of the protein. These results support a role for HmaERF87 as a positive regulator of H. macrophylla resistance to leaf spot disease and provide a candidate gene for further studies of disease resistance in hydrangea.

Plant Proteins

Engineering the efficient Exo-Cas12i2 for MITE manipulation in rice.

Exo-Cas12i2 v1, a fusion of the 5' exonucleases T5E and PapE, facilitates editing of TA-rich regions and mediates deletions of large genomic fragments. Exo-Cas12i2 v1-driven MITE manipulation enables precise regulation of genes involved in gibberellin-mediated cell elongation and root ethylene responses to generate favorable agronomic traits.

Oryza

Genetic basis and role of exotic accessions in cultivated cotton fiber quality improvement.

Exotic Gossypium accessions still harbor QTL&#x2011;validated alleles that, combined with CRISPR pyramiding and genomic selection, can break the entrenched fiber length-strength trade&#x2011;off. Cotton's four independent domestications twice in diploids and twice in allotetraploids offer a natural experiment in fiber improvement. Synthesizing three decades of data, we chart how polyploidy, selection and modern breeding have repeatedly reshaped the Gossypium genome. More than 15,000 quantitative trait locus (QTL) and genome wide association mapping studies (GWAS) hits converge on a handful of chromosomal "hotspots"; new MAGIC, NAM, NIL and long-read resources now narrow these peaks to&#x2009;<&#x2009;200&#xa0;kb, resolving causal genes such as GhHOX3, GhZF14 and GhMYB7. Multi-omics evidence links auxin, ethylene, gibberellin, brassinosteroid and strigolactone signaling to HDZIP IV, MYB, bHLH/HLH and ERF networks that drive fiber initiation, extreme cell elongation and cellulose deposition. Population genomics shows that&#x2009;~&#x2009;40% of favorable fiber alleles are fixed in elite Gossypium hirsutum, yet wild diploids and landraces still harbor variants that could break the length strength trade-off. We propose a three-step roadmap genomic selection, CRISPR gene pyramiding and accelerated introgression to expand cotton's genetic base and deliver fibers suited to sustainable textile demands.

Gossypium

Seed shattering habit in millets and the secrets of the abscission layer - a comprehensive review.

Though seed shattering continues to be a significant barrier affecting yield stability and harvesting efficiency in millets and other grasses, millets are increasingly acknowledged as climate-resilient, nutrient-rich 2007cereal crops with the potential to strengthen global nutritional and food security under the combined pressures of climate change, population growth, and limited natural resources. Since strong artificial selection favoured non-shattering phenotypes during domestication, seed shattering, an adaptive trait in wild species that promotes seed dispersal through the formation and activation of specialised abscission layers, became a distinguishing feature of cultivated cereals. With a focus on the morphological, physiological, hormonal, and genetic modulation of the abscission zone, this article summarizes the state of the art regarding seed shattering in millets. Abscission layer morphology, location, and lignification vary greatly among grasses, from well-defined lignified zones in rice and sorghum to non-lignified and anatomically subtle zones in Setaria and Panicum species. Cell wall-modifying enzymes like polygalacturonases, cellulases, expansins, and pectin methylesterases that mediate middle lamella degradation are modulated by coordinated hormonal signalling involving auxin, ethylene, and abscisic acid, which controls the timing and progression of cell separation at the physiological level. Domestication-related genes, including SH1, qSH1, SH4, and LES1, demonstrate convergent evolutionary mechanisms controlling abscission layer development in a variety of grass lineages at the molecular level. Understanding these regulatory networks has been greatly enhanced by recent developments in transcriptomics, functional genomics, and genome sequencing in both model species and underused millets. The role of millets as climate-smart cereals for sustainable future agriculture is reinforced by the integration of anatomical, physiological, and genetic insights, which offer a solid basis for targeted breeding and genome-editing strategies intended to improve seed retention, enhance yield stability, and increase harvest efficiency.

Abscission Layer

Research progress on the regulatory mechanisms of the PSY promoter.

Carotenoids are essential pigments in the plant photosynthetic apparatus, functioning in light harvesting, photoprotection, and signal transduction, and serving as precursors of vital nutrients such as vitamin A. Phytoene synthase (PSY) is the first rate-limiting enzyme in the plant carotenoid biosynthetic pathway, and its transcriptional regulation primarily depends on cis-acting promoter elements, associated transcription factors, and epigenetic status. The PSY promoter region contains core cis-elements as well as multiple light-, hormone-, and stress-responsive elements, which collectively function as key regulatory sites governing spatiotemporal expression. This review systematically summarizes recent advances in PSY promoter regulation by plant hormones (e.g., abscisic acid, ethylene, jasmonic acid), environmental factors (light signaling, temperature, salinity, and drought), and epigenetic mechanisms (DNA methylation, histone modifications, and chromatin remodeling). In addition, the application of transgenic and biotechnological approaches to PSY promoter regulation is further summarized. Including promoter sequence engineering with precise editing of cis-elements and promoter-targeted CRISPR activation/interference (CRISPRa/i) for tunable transcriptional control. Emphasis is placed on how these signals are integrated at the promoter level. Deeper insights into these mechanisms will provide both theoretical foundations and practical strategies for enhancing carotenoid accumulation and stress tolerance in crops through molecular design.

Promoter Regions, Genetic