A commitment for life: Decades of unraveling the molecular mechanisms behind seed dormancy and germination

Hormonomics profiles revealed the mechanisms of cold stratification in breaking the dormancy during seed germination and emergence process of Polygonatum sibiricum Red

Polygonatum sibiricum Red, known as Huangjing in Chinese, is a perennial plant valued in traditional Chinese medicine and is a nutritional food ingredient. With increasing market demand outpacing wild resource availability, cultivation has become essential for sustainable production. However, the cultivation of P. sibiricum is challenged by the double dormancy characteristics of seeds, which include embryo and physiological dormancy. This affected the germination of seeds and the establishment of seedlings. This study investigates the role of plant hormones in breaking seed dormancy and regulating germination and emergence in P. sibiricum. We found that cold stratification at 4°C for over 70 d significantly alleviates seed dormancy, associated with changes in endogenous hormone levels. Auxin, gibberellin, abscisic acid, cytokinin, salicylic acid, jasmonic acid, and ethylene were identified as key players in these processes. Exogenous applications of GA3 and 2-coumarate (2-hydroxycinnamic acid) significantly enhanced seed germination, while 6-BA and GA3 promoted corm growth and development. In conclusion, our research provides insights into the hormonal regulation of seed dormancy and germination in P. sibiricum, offering valuable strategies for improving cultivation practices. Further studies are needed to explore the specific mechanisms of hormone interactions and to develop optimized germination and seedling establishment strategies for this medicinally important plant.

Planting Genomes in the Wild: Arabidopsis from Genetics History to the Ecology and Evolutionary Genomics Era

The genetics model system Arabidopsis thaliana (L.) Heynh. lives across a vast geographic range with contrasting climates, in response to which it has evolved diverse life histories and phenotypic adaptations. In the last decade, the cataloging of worldwide populations, DNA sequencing of whole genomes, and conducting of outdoor field experiments have transformed it into a powerful evolutionary ecology system to understand the genomic basis of adaptation. Here, we summarize new insights on Arabidopsis following the coordinated efforts of the 1001 Genomes Project, the latest reconstruction of biogeographic and demographic history, and the systematic genomic mapping of trait natural variation through 15 years of genome-wide association studies. We then put this in the context of local adaptation across climates by summarizing insights from 73 Arabidopsis outdoor common garden experiments conducted to date. We conclude by highlighting how molecular and genomic knowledge of adaptation can help us to understand species' (mal)adaptation under ongoing climate change.

Phase separation as a key mechanism in plant development, environmental adaptation, and abiotic stress response

Liquid-liquid phase separation is a fundamental biophysical process in which biopolymers, such as proteins, nucleic acids, and their complexes, spontaneously demix into distinct coexisting phases. This phenomenon drives the formation of membraneless organelles-cellular subcompartments without a lipid bilayer that perform specialized functions. In plants, phase-separated biomolecular condensates play pivotal roles in regulating gene expression, from genome organization to transcriptional and post-transcriptional processes. In addition, phase separation governs plant-specific traits, such as flowering and photosynthesis. As sessile organisms, plants have evolved to leverage phase separation for rapid sensing and response to environmental fluctuations and stress conditions. Recent studies highlight the critical role of phase separation in plant adaptation, particularly in response to abiotic stress. This review compiles the latest research on biomolecular condensates in plant biology, providing examples of their diverse functions in development, environmental adaptation, and stress responses. We propose that phase separation represents a conserved and dynamic mechanism enabling plants to adapt efficiently to ever-changing environmental conditions. Deciphering the molecular mechanisms underlying phase separation in plant stress responses opens new avenues for biotechnological strategies aimed at engineering stress-resistant crops. These advancements have significant implications for agriculture, particularly in addressing crop productivity in the face of climate change.

Map-based cloning of Zmccr3 and its network construction and validation for regulating maize seed germination

KEY MESSAGE

Map-based cloning of Zmccr3 for regulate SG and its molecular regulatory pathway was performed and validated. WGCNA, target genes/pathways during the process of seed dormancy formation were obtained. Seed dormancy (SD) and pre-harvest sprouting (PHS) affect the grain yield and quality of grain in cereal and hybrid seed production. Although the benefits of studying SD and seed germination (SG) during seed development are well established, research into the genetic variation and molecular regulation of SD, particularly during the transition from SD to SG, remains very limited. In this study, bulked segregant analysis (BSA) and linkage analysis were used to map the QTL for the maize vp16 mutant of PHS. Using genetic and biological methods, the candidate gene was identified as Zmccr3, encoding cinnamoyl-CoA reductase 3 (ccr3), which is involved in the phenylalanine pathway of lignin metabolism and affects SG. Based on RNA-seq (RNA sequencing) at two stages of grain development with extreme PHS traits, a weighted gene coexpression network analysis (WGCNA) related to SD and SG formation was constructed, and ten target genes and three pathways during the transition from SD to SG were identified. Simultaneously, the Zmccr3 pathway was established and validated, involving upstream lipid metabolism, redox modification and degradation of cell wall oligosaccharides (as electrophilic compounds), regulation of GA signaling and intracellular ROS homeostasis, and downstream oxidation of cell wall lignin units and synthesis of phenolic compounds that affect endosperm weakening and cell wall loosening, ultimately regulating SG or SD. Therefore, we propose the Zmccr3 hypothesis to elucidate its possible functions. These findings have important theoretical and practical implications for understanding the genetic basis of PHS and SD in maize, increasing genetic resources and improving traits.

Phenotypic Plasticity and Stability in Plants: Genetic Mechanisms, Environmental Adaptation, Evolutionary Implications, and Future Directions

The phenotypic display, survival, and reproduction of organisms depend on genotype-environment interactions that drive development, evolution, and diversity. Biological systems exhibit two basic but paradoxical features that contribute to developmental robustness: plasticity and stability. However, the understanding of these concepts remains ambiguous. The morphology and structure of plant reproductive organs-flowers and fruits-exhibit substantial stability but display a certain level of plasticity under environmental changes, thus representing promising systems for the study of how stability and plasticity jointly govern plant development and evolution. Beyond the genes underlying organ formation, certain genes may maintain stability and induce plasticity. Variations in relevant genes can induce developmental repatterning, thereby altering stability or plasticity under light and temperature fluctuations, which often affects fitness. The regulation of developmental robustness in plant vegetative organs involves transcriptional and post-transcriptional regulation, epigenetics, and phase separation; however, these mechanisms in the reproductive organs of flowering plants remain poorly investigated. Moreover, genes that specifically determine phenotypic plasticity have rarely been cloned. This review clarifies the concepts and attributes of phenotypic plasticity and stability and further proposes potential avenues and a paradigm to investigate the underlying genes and elucidate how plants adapt and thrive in diverse environments, which is crucial for the design of genetically modified crops.

A DOF transcriptional repressor-gibberellin feedback loop plays a crucial role in modulating light-independent seed germination

Plants have evolved several strategies to cope with the ever-changing environment. One example of this is given by seed germination, which must occur when environmental conditions are suitable for plant life. In the model system Arabidopsis thaliana seed germination is induced by light; however, in nature, seeds of several plant species can germinate regardless of this stimulus. While the molecular mechanisms underlying light-induced seed germination are well understood, those governing germination in the dark are still vague, mostly due to the lack of suitable model systems. Here, we employ Cardamine hirsuta, a close relative of Arabidopsis, as a powerful model system to uncover the molecular mechanisms underlying light-independent germination. By comparing Cardamine and Arabidopsis, we show that maintenance of the pro-germination hormone gibberellin (GA) levels prompt Cardamine seeds to germinate under both dark and light conditions. Using genetic and molecular biology experiments, we show that the Cardamine DOF transcriptional repressor DOF AFFECTING GERMINATION 1 (ChDAG1), homologous to the Arabidopsis transcription factor DAG1, is involved in this process functioning to mitigate GA levels by negatively regulating GA biosynthetic genes ChGA3OX1 and ChGA3OX2, independently of light conditions. We also demonstrate that this mechanism is likely conserved in other Brassicaceae species capable of germinating in dark conditions, such as Lepidium sativum and Camelina sativa. Our data support Cardamine as a new model system suitable for studying light-independent germination studies. Exploiting this system, we have also resolved a long-standing question about the mechanisms controlling light-independent germination in plants, opening new frontiers for future research.

Plant ubiquitin E2 enzymes UBC32, UBC33, and UBC34 are involved in ERAD and function in host stress tolerance

BACKGROUND

Endoplasmic reticulum (ER)-associated protein degradation (ERAD) is a critical component of the ER-mediated protein quality control (ERQC) system and plays a vital role in plant stress responses. However, the ubiquitination machinery underlying plant ERAD-particularly the ubiquitin-conjugating enzymes (E2s)-and their contributions to stress tolerance remain poorly understood.

RESULTS

In this study, we identified UBC32, UBC33, and UBC34 as ER-localized ubiquitin E2 enzymes involved in ERAD and demonstrated their roles in biotic and abiotic stress tolerance in tomato (Solanum lycopersicum) and Arabidopsis (Arabidopsis thaliana). In response to biotic stress, UBC33 and UBC34 collectively contribute more substantially than UBC32 to plant immunity against Pseudomonas syringae pv. tomato (Pst). Under abiotic stress and ER stress induced by tunicamycin (TM), all three E2s play important roles. Notably, mutation of UBC32 enhances tolerance to TM-induced ER stress, whereas the loss of function in UBC33 or UBC34 suppresses this response. Additionally, UBC32, UBC33, and UBC34 act synergistically in Arabidopsis seed germination under salt stress and abscisic acid (ABA) treatment. While the single mutants atubc32, atubc33, and atubc34 exhibit germination rates comparable to Col-0 under salt stress or ABA treatment, the double mutants atubc32/33, atubc32/34, and atubc33/34 show a significantly greater reduction in germination rate. Interestingly, the atubc32/33/34 triple mutant exhibits a seed germination rate under salt stress and ABA treatment, as well as a level of host immunity to Pst, comparable to that of the atubc33/34 and atubc32/34 double mutants.

CONCLUSIONS

Our findings establish UBC32, UBC33, and UBC34 as key components of the plant ERAD machinery, contributing to plant tolerance to both abiotic and biotic stress. Despite their close phylogenetic relationship, these E2 enzymes exhibit redundant, synergistic, or antagonistic roles depending on the specific stress response pathway, underscoring the complexity of their functional interactions.

A space for time. Exploring temporal regulation of plant development across spatial scales

Plants continuously undergo change during their life cycle, experiencing dramatic phase transitions altering plant form, and regulating the assignment and progression of cell fates. The relative timing of developmental events is tightly controlled and involves integration of environmental, spatial, and relative age-related signals and actors. While plant phase transitions have been studied extensively and many of their regulators have been described, less is known about temporal regulation on a smaller, cell-level scale. Here, using examples from both plant and animal systems, we outline time-dependent changes. Looking at systemic scale changes, we discuss the timing of germination, juvenile-to-adult transition, flowering, and senescence, together with regeneration timing. Switching to temporal regulation on a cellular level, we discuss several instances from the animal field in which temporal control has been examined extensively at this scale. Then, we switch back to plants and summarize examples where plant cell-level changes are temporally regulated. As time cannot easily be separated from signaling derived from the environment and tissue context, we next discuss factors that have been implicated in controlling the timing of developmental events, reviewing temperature, photoperiod, nutrient availability, as well as tissue context and mechanical cues on the cellular scale. Afterwards, we provide an overview of mechanisms that have been shown or implicated in the temporal control of development, considering metabolism, division control, mobile signals, epigenetic regulation, and the action of transcription factors. Lastly, we look at remaining questions for the future study of developmental timing in plants and how recent technical advancement can enable these efforts.

Light regulates seed dormancy through FHY3-mediated activation of ACC OXIDASE 1 in Arabidopsis

Seed dormancy enables plants to delay germination until conditions are favorable for the survival of the next generation. Seed dormancy and germination are controlled by a combination of external and internal signals, in which light and ethylene act as critical regulators. However, how light and ethylene are interlinked to control these two processes remains to be investigated. Here, we show that ethylene and its precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), promote seed germination under light. Light facilitates the conversion of ACC to ethylene, in which phytochrome B (phyB) and FAR-RED ELONGATED HYPOCOTYL3 (FHY3) are functionally required. ACC oxidases (ACOs) catalyze the conversion of ACC to ethylene, among which ACO1 is specifically and predominantly expressed in imbibed seeds. Ethylene induces FHY3 protein accumulation in imbibed seeds, whereby FHY3 directly binds to ACO1 promoter and specifically mediates light-promoted ACO1 expression. Light promotes ACO1 protein accumulation. Overexpression of ACO1 significantly promotes seed germination, and almost completely restores the dormant defect of fhy3 loss-of-function mutants. In summary, this study reveals an ethylene-responsive regulatory cascade of phyB-FHY3-ACO1 that integrates external light input with internal factors to regulate seed dormancy and germination.

Nitrate attenuates abscisic acid signaling via NIN-LIKE PROTEIN8 in Arabidopsis seed germination

Abscisic acid (ABA) suppresses Arabidopsis (Arabidopsis thaliana) seed germination and post-germinative growth. Nitrate stimulates seed germination, but whether it directly regulates ABA signaling and the associated underlying molecular mechanisms remain unknown. Here, we showed that nitrate alleviates the repressive effects of ABA on seed germination independently of the nitric oxide (NO) pathway. Moreover, nitrate attenuates ABA signaling activated by ABSCISIC ACID INSENSITIVE3 (ABI3) and ABI5, two critical transcriptional regulators of the ABA pathway. Mechanistic analyses demonstrated that ABI3 and ABI5 physically interact with the nitrate signaling-related core transcription factor NIN-LIKE PROTEIN 8 (NLP8). After ABA treatment, NLP8 suppresses ABA responses during seed germination without affecting ABA content. Notably, nitrate represses ABA signaling mainly through NLP8. Genetic analyses showed that NLP8 acts upstream of ABI3 and ABI5. Specifically, NLP8 inhibits the transcriptional functions of ABI3 and ABI5, as well as their ABA-induced accumulation. Additionally, NLP8 overexpression largely suppresses the ABA hypersensitivity of mutant plants exhibiting impaired NO biosynthesis or signaling. Collectively, our study reveals that nitrate counteracts the inhibitory effects of ABA signaling on seed germination and provides mechanistic insights into the NLP8-ABI3/ABI5 interactions and their antagonistic relationships in ABA signaling.

Integrated analyses provide insights into the seed dormancy mechanisms of the endangered plant Sinojackia sarcocarpa

Sinojackia sarcocarpa, an endangered ornamental plant endemic to China, faces germination challenges that contribute to its endangered status. The mechanisms of its seed dormancy are not well understood. This study used morphological, physiological, transcriptomic, and gene function analyses to investigate these mechanisms. Our research shows that seed dormancy in Sinojackia sarcocarpa involves both physical and physiological factors. We found that removing the hard endocarp and applying gibberellic acid can effectively break dormancy. Transcriptomic analysis identified 2218 up-regulated and 374 down-regulated genes during germination. Notably, DOG1-domain genes SsDOGL4, SsTGA9, and SsTGA10 were significantly downregulated, while SsDOG1 was not. Additionally, overexpression of SsDOGL4 in Arabidopsis endosperm was found to enhance seed dormancy. Collectively, these findings offer significant insights into the mechanisms underlying seed dormancy in this endangered plant species.

DOG1 controls dormancy independently of ABA core signaling kinases regulation by preventing AFP dephosphorylation through AHG1

Seed dormancy determines germination timing, influencing seed plant adaptation and overall fitness. DELAY OF GERMINATION 1 (DOG1) is a conserved central regulator of dormancy cooperating with the phytohormone abscisic acid (ABA) through negative regulation of ABA HYPERSENSITIVE GERMINATION (AHG) 1 and AHG3 phosphatases. The current molecular mechanism of DOG1 signaling proposes it regulates the activation of central ABA-related SnRK2 kinases. Here, we unveil DOG1's functional autonomy from the regulation of ABA core signaling components and unravel its pivotal control over the activation of ABSCISIC ACID INSENSITIVE FIVE BINDING PROTEINs (AFPs). Our data revealed a molecular relay in which AFPs' genuine activation by AHG1 is contained by DOG1 to prevent the breakdown of maturation-imposed ABA responses independently of ABA-related kinase activation status. This work offers a molecular understanding of how plants fine-tune germination timing, while preserving seed responsiveness to adverse environmental cues, and thus represents a milestone in the realm of conservation and breeding programs.

Stress sensing and response through biomolecular condensates in plants

Plants have developed intricate mechanisms for rapid and efficient stress perception and adaptation in response to environmental stressors. Recent research highlights the emerging role of biomolecular condensates in modulating plant stress perception and response. These condensates function through numerous mechanisms to regulate cellular processes such as transcription, translation, RNA metabolism, and signaling pathways under stress conditions. In this review, we provide an overview of current knowledge on stress-responsive biomolecular condensates in plants, including well-defined condensates such as stress granules, processing bodies, and the nucleolus, as well as more recently discovered plant-specific condensates. By briefly referring to findings from yeast and animal studies, we discuss mechanisms by which plant condensates perceive stress signals and elicit cellular responses. Finally, we provide insights for future investigations on stress-responsive condensates in plants. Understanding how condensates act as stress sensors and regulators will pave the way for potential applications in improving plant resilience through targeted genetic or biotechnological interventions.

Evaluation of morphological and cytotoxic effects of minoxidil on Phaseolus vulgaris L. as a plant model

The increasing presence of drugs in the environment has triggered a pollution crisis on a global scale, generating concern about their ecotoxicological effects on ecosystems. In this context, minoxidil, a vasodilator drug widely used in the treatment of androgenic alopecia, has been scarcely investigated in plant systems. Therefore, this study evaluated the morphological and cytotoxic effects of minoxidil on Phaseolus vulgaris L as a bioindicator. P. vulgaris seeds were exposed to different concentrations of minoxidil (0.0, 0.25, 0.5, 1, 1.25, 2.5 and 5 mg/L) and parameters such as germination, root growth, mitotic index and frequency of chromosomal abnormalities were assessed. The results showed a significant inhibition of germination (75-76%) and root growth (52.6-55.3%) at high concentrations of minoxidil (2.55 mg/L-5 mg/L). In addition, a decrease in the mitotic index (8.2) and an increase in the frequency of chromosomal abnormalities (10.2) were observed, suggesting a cytotoxic effect. These findings show that minoxidil, even at low concentrations, can have adverse effects on the morphology and cell division of P. vulgaris. This study demonstrates the potential of plants as tools to evaluate the phytotoxicity and cytotoxicity of drugs and highlights the need to implement measures to reduce the contamination of these drugs in the environment.

Arachis hypogaea monoacylglycerol lipase AhMAGL3b participates in lipid metabolism

BACKGROUND

Monoacylglycerol lipase (MAGL) belongs to the serine hydrolase family; it catalyzes MAG to produce glycerol and free fatty acids (FFAs), which is the final step in triacylglycerol (TAG) hydrolysis. The effects of MAGL on comprehensive lipid metabolism and plant growth and development have not been elucidated, especially in Arachis hypogaea, an important oil crop.

RESULTS

Herein, AhMAGL3b encoding a protein with both hydrolase and acyltransferase regions, a member of MAGL gene family, was cloned and overexpressed in Arabidopsis thaliana. A total of 9 homozygous T3 generation transgenic lines were obtained. Compared with wild type (WT), overexpression (OE) of AhMAGL3b had no obvious growth inhibition by investigation of agronomic traits, including growth and photosynthetic parameters. The leaf fatty acid (FA) content was increased by 12.1-27.4% in AhMAGL3b-OE lines, while seed oil content was decreased by 10.7-17.3%. Furthermore, the overexpression of AhMAGL3b resulted in higher soluble sugar and starch content, and lower total soluble protein content in both leaves and seeds. Additionally, during seed germination, AhMAGL3b-OE seeds were more dormant than that of WT and the sensitivity to abscisic acid (ABA) treatment was decreased.

CONCLUSIONS

Taken together, our results indicate that AhMAGL3b is involved in homeostasis among carbohydrates, lipids and protein in A. hypogaea.

The BRAHMA-associated SWI/SNF chromatin remodeling complex controls Arabidopsis seed quality and physiology

The SWI/SNF (SWItch/Sucrose Non-Fermentable) chromatin remodeling complex is involved in various aspects of plant development and stress responses. Here, we investigated the role of BRM (BRAHMA), a core catalytic subunit of the SWI/SNF complex, in Arabidopsis thaliana seed biology. brm-3 seeds exhibited enlarged size, reduced yield, increased longevity, and enhanced secondary dormancy, but did not show changes in primary dormancy or salt tolerance. Some of these phenotypes depended on the expression of DOG1, a key regulator of seed dormancy, as they were restored in the brm-3 dog1-4 double mutant. Transcriptomic and metabolomic analyses revealed that BRM and DOG1 synergistically modulate the expression of numerous genes. Some of the changes observed in the brm-3 mutant, including increased glutathione levels, depended on a functional DOG1. We demonstrated that the BRM-containing chromatin remodeling complex directly controls secondary dormancy through DOG1 by binding and remodeling its 3' region, where the promoter of the long noncoding RNA asDOG1 is located. Our results suggest that BRM and DOG1 cooperate to control seed physiological properties and that BRM regulates DOG1 expression through asDOG1. This study reveals chromatin remodeling at the DOG1 locus as a molecular mechanism controlling the interplay between seed viability and dormancy.

Diverse functional interactions between ABA and ethylene in plant development and responses to stress

Abscisic acid (ABA) and ethylene are two essential hormones that play crucial roles throughout the entire plant life cycle and in their tolerance to abiotic or biotic stress. In recent decades, increasing research has revealed that, in addition to their individual roles, these two hormones are more likely to function through their interactions, forming a complex regulatory network. More importantly, their functions change and their interactions vary from synergistic to antagonistic depending on the specific plant organ and development stage, which is less focused, compared and systematically summarized. In this review, we first introduce the general synthesis and action signaling pathways of these two plant hormones individually and their interactions in relation to seed dormancy and germination, primary root growth, shoot development, fruit ripening, leaf senescence and abscission, and stomatal movement regulation under both normal and stress conditions. A better understanding of the complex interactions between ABA and ethylene will enhance our knowledge of how plant hormones regulate development and respond to stress and may facilitate the development of crops with higher yields and greater tolerance to stressful environments through tissue-specific genetic modifications in the future.

Regulation of seed dormancy by histone post-translational modifications in the model plant Arabidopsis thaliana

Plants synchronize their growth and development with environmental changes, which is critical for their survival. Among their life cycle transitions, seed germination is key for ensuring the survival and optimal growth of the next generation. However, even under favorable conditions, often germination can be blocked by seed dormancy, a regulatory multilayered checkpoint integrating internal and external signals. Intricate genetic and epigenetic mechanisms underlie seed dormancy establishment, maintenance, and release. In this review, we focus on recent advances that shed light on the complex mechanisms associated with physiological dormancy, prevalent in seed plants, with Arabidopsis thaliana serving as a model. Here, we summarize the role of multiple epigenetic regulators, but with a focus on histone modifications such as acetylation and methylation, that finely tune dormancy responses and influence dormancy-associated gene expression. Understanding these mechanisms can lead to a better understanding of seed biology in general, as well as resulting in the identification of possible targets for breeding climate-resilient plants.

Sleeping but not defenceless: seed dormancy and protection

To ensure their vital role in disseminating the species, dormant seeds have developed adaptive strategies to protect themselves against pathogens and predators. This is orchestrated through the synthesis of an array of constitutive defences that are put in place in a developmentally regulated manner, which are the focus of this review. We summarize the defence activity and the nature of the molecules coming from the exudate of imbibing seeds that leak into their vicinity, also referred to as the spermosphere. As a second layer of protection, the dual role of the seed coat will be discussed; as a physical barrier and a multi-layered reservoir of defence compounds that are synthesized during seed development. Since imbibed dormant seeds can persist in the soil for extensive periods, we address the question of whether during this time a constitutively regulated defence programme is switched on to provide further protection, via the well-defined pathogenesis-related (PR) protein family. In addition, we review the hormonal and signalling pathways that might be involved in the interplay between dormancy and defence and point out questions that need further attention.

Modulation in the ratio of abscisic acid to gibberellin level determines genetic variation of seed dormancy in barley (Hordeum vulgare L.)

Abscisic acid (ABA) and gibberellin (GA) are major regulators of seed dormancy, an adaptive trait closely associated with preharvest sprouting. This study examined transcriptional regulation of ABA and GA metabolism genes and modulation of ABA and GA levels in seeds of barley genotypes exhibiting a range of dormancy phenotype. We observed a very strong negative correlation between genetic variation in seed germination and embryonic ABA level (r = 0.85), which is regulated by transcriptional modulation of HvNCED1 and/or HvCYP707A genes. A strong positive correlation was evident between variation in seed germination and GA level (r = 0.64), mediated via transcriptional regulation of GA biosynthesis genes, HvGA20ox2 and/or HvGA3oxs, and GA catabolism genes, HvGA2ox3 and/or HvGA3ox6. Modulation of the ABA and GA levels in the genotypes led to the prevalence of ABA to GA level ratio that exhibited a very strong negative correlation (r = 0.84) with seed germination, highlighting the importance of a shift in ABA/GA ratio in determining genetic variation of dormancy in barley seeds. Our results overall show that transcriptional regulation of specific ABA and GA metabolism genes underlies genetic variation in ABA/GA ratio and seed dormancy, reflecting the potential use of these genes as molecular tools for enhancing preharvest sprouting resistance in barley.

Ethylene, a Signaling Compound Involved in Seed Germination and Dormancy

The present review is focused on current findings on the involvement of ethylene in seed biology. The responsiveness of seeds to ethylene depends on the species and the dormancy status, improving concentrations ranging from 0.1 to 200 μL L-1. The signaling pathway of ethylene starts with its binding to five membrane-anchored receptors, which results in the deactivation of Constitutive Triple Response 1 (CTR1, a protein kinase) that does not exert its inhibitory effect on Ethylene Insensitive 2 (EIN2) by phosphorylating its cytosolic C-terminal domain. An analysis of germination in the presence of inhibitors of ethylene synthesis or action, and using seeds from mutant lines altered in terms of the genes involved in ethylene synthesis (acs) and the signaling pathway (etr1, ein2, ein4, ctr1 and erf1), demonstrates the involvement of ethylene in the regulation of seed dormancy. The promoting effect of ethylene is also regulated through crosstalk with abscisic acid (ABA) and gibberellins (GAs), essential hormones involved in seed germination and dormancy, and Reactive Oxygen Species (ROS). Using a mutant of the proteolytic N-degron pathway, Proteolysis (PRT6), the Ethylene Response Factors (ERFs) from group VII (HRE1, HRE2, RAP 2.2, RAP2.3 and RAP 2.12) have also been identified as being involved in seed insensitivity to ethylene. This review highlights the key roles of EIN2 and EIN3 in the ethylene signaling pathway and in interactions with different hormones and discusses the responsiveness of seeds to ethylene, depending on the species and the dormancy status.

Current Insights into Weak Seed Dormancy and Pre-Harvest Sprouting in Crop Species

During the domestication of crops, seed dormancy has been reduced or eliminated to encourage faster and more consistent germination. This alteration makes cultivated crops particularly vulnerable to pre-harvest sprouting, which occurs when mature crops are subjected to adverse environmental conditions, such as excessive rainfall or high humidity. Consequently, some seeds may bypass the normal dormancy period and begin to germinate while still attached to the mother plant before harvest. Grains affected by pre-harvest sprouting are characterized by increased levels of α-amylase activity, resulting in poor processing quality and immediate grain downgrading. In the agriculture industry, pre-harvest sprouting causes annual economic losses exceeding USD 1 billion worldwide. This premature germination is influenced by a complex interplay of genetic, biochemical, and molecular factors closely linked to environmental conditions like rainfall. However, the exact mechanism behind this process is still unclear. Unlike pre-harvest sprouting, vivipary refers to the germination process and the activation of α-amylase during the soft dough stage, when the grains are still immature. Mature seeds with reduced levels of ABA or impaired ABA signaling (weak dormancy) are more susceptible to pre-harvest sprouting. While high seed dormancy can enhance resistance to pre-harvest sprouting, it can lead to undesirable outcomes for most crops, such as non-uniform seedling establishment after sowing. Thus, resistance to pre-harvest sprouting is crucial to ensuring productivity and sustainability and is an agronomically important trait affecting yield and grain quality. On the other hand, seed color is linked to sprouting resistance; however, the genetic relationship between both characteristics remains unresolved. The identification of mitogen-activated protein kinase kinase-3 (MKK3) as the gene responsible for pre-harvest sprouting-1 (Phs-1) represents a significant advancement in our understanding of how sprouting in wheat is controlled at the molecular and genetic levels. In seed maturation, Viviparous-1 (Vp-1) plays a crucial role in managing pre-harvest sprouting by regulating seed maturation and inhibiting germination through the suppression of α-amylase and proteases. Vp-1 is a key player in ABA signaling and is essential for the activation of the seed maturation program. Mutants of Vp-1 exhibit an unpigmented aleurone cell layer and exhibit precocious germination due to decreased sensitivity to ABA. Recent research has also revealed that TaSRO-1 interacts with TaVp-1, contributing to the regulation of seed dormancy and resistance to pre-harvest sprouting in wheat. The goal of this review is to emphasize the latest research on pre-harvest sprouting in crops and to suggest possible directions for future studies.

Non-thermal atmospheric-pressure plasma exposure as a practical method for improvement of Brassica juncea seed germination

Here we report that non-thermal atmospheric-pressure plasma exposure can improve Brassica juncea (leaf mustard) seed germination rate from 50 % to 98 %. The commercially relevant germination rate was achieved by plasma exposure for only 10 minutes and the effect sustains at least for one month under an appropriate storage condition. Improved germination by plasma exposure was also observed for Brassica rapa subsp. pekinensis (Chinese cabbage) seeds. The plasma device used is simple. No pure gas flow system is necessary and it is easy to handle. A large number of seeds can be treated by simply scaling up the device. Plasma exposure can be a practical method for improving seed germination of crop plants important for agriculture.

Transcriptional Control of Seed Life: New Insights into the Role of the NAC Family

Transcription factors (TFs) regulate gene expression by binding to specific sequences on DNA through their DNA-binding domain (DBD), a universal process. This update conveys information about the diverse roles of TFs, focusing on the NACs (NAM-ATAF-CUC), in regulating target-gene expression and influencing various aspects of plant biology. NAC TFs appeared before the emergence of land plants. The NAC family constitutes a diverse group of plant-specific TFs found in mosses, conifers, monocots, and eudicots. This update discusses the evolutionary origins of plant NAC genes/proteins from green algae to their crucial roles in plant development and stress response across various plant species. From mosses and lycophytes to various angiosperms, the number of NAC proteins increases significantly, suggesting a gradual evolution from basal streptophytic green algae. NAC TFs play a critical role in enhancing abiotic stress tolerance, with their function conserved in angiosperms. Furthermore, the modular organization of NACs, their dimeric function, and their localization within cellular compartments contribute to their functional versatility and complexity. While most NAC TFs are nuclear-localized and active, a subset is found in other cellular compartments, indicating inactive forms until specific cues trigger their translocation to the nucleus. Additionally, it highlights their involvement in endoplasmic reticulum (ER) stress-induced programmed cell death (PCD) by activating the vacuolar processing enzyme (VPE) gene. Moreover, this update provides a comprehensive overview of the diverse roles of NAC TFs in plants, including their participation in ER stress responses, leaf senescence (LS), and growth and development. Notably, NACs exhibit correlations with various phytohormones (i.e., ABA, GAs, CK, IAA, JA, and SA), and several NAC genes are inducible by them, influencing a broad spectrum of biological processes. The study of the spatiotemporal expression patterns provides insights into when and where specific NAC genes are active, shedding light on their metabolic contributions. Likewise, this review emphasizes the significance of NAC TFs in transcriptional modules, seed reserve accumulation, and regulation of seed dormancy and germination. Overall, it effectively communicates the intricate and essential functions of NAC TFs in plant biology. Finally, from an evolutionary standpoint, a phylogenetic analysis suggests that it is highly probable that the WRKY family is evolutionarily older than the NAC family.

Preharvest Sprouting in Quinoa: A New Screening Method Adapted to Panicles and GWAS Components

The introduction of quinoa into new growing regions and environments is of interest to farmers, consumers, and stakeholders around the world. Many plant breeding programs have already started to adapt quinoa to the environmental and agronomic conditions of their local fields. Formal quinoa breeding efforts in Washington State started in 2010, led by Professor Kevin Murphy out of Washington State University. Preharvest sprouting appeared as the primary obstacle to increased production in the coastal regions of the Pacific Northwest. Preharvest sprouting (PHS) is the undesirable sprouting of seeds that occurs before harvest, is triggered by rain or humid conditions, and is responsible for yield losses and lower nutrition in cereal grains. PHS has been extensively studied in wheat, barley, and rice, but there are limited reports for quinoa, partly because it has only recently emerged as a problem. This study aimed to better understand PHS in quinoa by adapting a PHS screening method commonly used in cereals. This involved carrying out panicle-wetting tests and developing a scoring scale specific for panicles to quantify sprouting. Assessment of the trait was performed in a diversity panel (N = 336), and the resulting phenotypes were used to create PHS tolerance rankings and undertake a GWAS analysis (n = 279). Our findings indicate that PHS occurred at varying degrees across a subset of the quinoa germplasm tested and that it is possible to access PHS tolerance from natural sources. Ultimately, these genotypes can be used as parental lines in future breeding programs aiming to incorporate tolerance to PHS.

Molecular mechanisms underlying the signal perception and transduction during seed germination

QuerySeed germination is a vital step in the life cycle of a plant, playing a significant role in seedling establishment and crop yield potential. It is also an important factor in the conservation of plant germplasm resources. This complex process is influenced by a myriad of factors, including environmental conditions, the genetic makeup of the seed, and endogenous hormones. The perception of these environmental signals triggers a cascade of intricate signal transduction events that determine whether a seed germinates or remains dormant. Despite considerable progress in uncovering the molecular mechanisms governing these processes, many questions remain unanswered. In this review, we summarize the current progress in the molecular mechanisms underlying the perception of environmental signals and consequent signal transduction during seed germination, and discuss questions that need to be addressed to better understand the process of seed germination and develop novel strategies for germplasm improvement.

Identification of Quantitative Trait Loci and Candidate Genes Controlling Seed Dormancy in Eggplant (Solanum melongena L.)

Seed dormancy is a life adaptation trait exhibited by plants in response to environmental changes during their growth and development. The dormancy of commercial seeds is the key factor affecting seed quality. Eggplant seed dormancy is controlled by quantitative trait loci (QTLs), but reliable QTLs related to eggplant dormancy are still lacking. In this study, F2 populations obtained through the hybridization of paternally inbred lines with significant differences in dormancy were used to detect regulatory sites of dormancy in eggplant seeds. Three QTLs (dr1.1, dr2.1, and dr6.1) related to seed dormancy were detected on three chromosomes of eggplant using the QTL-Seq technique. By combining nonsynonymous sites within the candidate regions and gene functional annotation analysis, nine candidate genes were selected from three QTL candidate regions. According to the germination results on the eighth day, the male parent was not dormant, but the female parent was dormant. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to verify the expression of nine candidate genes, and the Smechr0201082 gene showed roughly the same trend as that in the phenotypic data. We proposed Smechr0201082 as the potential key gene involved in regulating the dormancy of eggplant seeds. The results of seed experiments with different concentrations of gibberellin A3 (GA3) showed that, within a certain range, the higher the gibberellin concentration, the earlier the emergence and the higher the germination rate. However, higher concentrations of GA3 may have potential effects on eggplant seedlings. We suggest the use of GA3 at a concentration of 200-250 mg·L-1 to treat dormant seeds. This study provides a foundation for the further exploration of genes related to the regulation of seed dormancy and the elucidation of the molecular mechanism of eggplant seed dormancy and germination.