Seed Science Research最新文献

Seeds are complex structures that serve as dispersal units in angiosperms. Seeds consist of three specialized tissues with distinct roles and molecular compositions. Hence, the characterization of the genetic regulators that act within individual seed tissues, and how their activity changes during seed development and germination, has been a primary focus of seed research. However, our knowledge of the spatiotemporal modulation of genetic regulators within seeds, across different seed cell types, has been limited by the resolution of available techniques. In the last few years, the development and application of single-cell technologies in plants have enabled the elucidation of gene networks involved in various developmental processes at the cellular level. Some studies have applied these technologies to seeds, enabling further characterization of seed development and germination at the cellular level. Here, we review the current status of the application of single-cell technologies to seeds and present a workflow for conducting single-cell transcriptomics. Additionally, we discuss the integration of single-cell multi-omics, aiming to demonstrate the potential of single-cell technologies in enhancing our comprehension of the spatiotemporal regulations governing seed development and germination.

Seed persistence, desiccation tolerance, and dormancy play a crucial role in plant population and community dynamics. However, these life-history traits remain largely understudied in perennial herbaceous species, particularly in tropical ecosystems. We evaluated the seed storage behaviour, potential longevity, soil seed bank, seed dormancy alleviation in the field and the effects of after-ripening temperature and time on seed dormancy alleviation in Carajasia cangae – an endangered perennial forb endemic to the ironstone outcrops of the Eastern Amazon. We performed germination experiments to examine the effect of storage conditions (−20, 5 and 28°C, as well as field storage) and time on seed viability, mean germination time and percentage. Our results suggested that C. cangae seeds form a transient soil seed bank and show orthodox storage behaviour. The seeds' longevity was favoured in all controlled storage conditions in relation to soil-stored seeds (field). However, the marked loss of seed viability in less than 1 year, regardless of storage condition, indicates a low potential for long-term germplasm conservation through seed banking. Seed dormancy was fully alleviated after 3 months of field storage during the dry season. Moreover, seeds stored for 6 months at 28°C had their dormancy partially alleviated, indicating that environmental conditions found throughout the dry season in the species habitat are required to alleviate its seed dormancy. A transient seed bank type is favoured by predictable seasonal variations in climate in the region, species iteroparity and seed dormancy alleviation during the dry season, which delays germination until the onset of the next rainy season.

The previous study indicated that ubiquitination is involved in the freezing tolerance of hydrated seeds. Parthenolide (PN), inducing the ubiquitination of MDM2, an E3 ring-finger ubiquitin ligase, adversely affects the freezing tolerance of hydrated lettuce seeds. Therefore, a proteomics analysis was conducted to identify PN's targets in hydrated seeds exposed to cooling conditions. Several pathways, including oxidative phosphorylation (KEGG00190), amino sugar and nucleotide sugar metabolism (KEGG00520), and biosynthesis of nucleotide sugars (KEGG01250), were enriched in the PN treatment under slow-cooling conditions (3°C h−1, P < 0.05). Among the proteins in oxidative phosphorylation, the expression of NADH dehydrogenases and ATP synthases (ATPsyn) decreased in PN treatment. In contrast, uncoupling proteins increased after PN treatment, which led to the dissociation of the electron transport chain from ATP synthesis. Treatments with rotenone, dicoumarol, and oligomycin (i.e., oxidative phosphorylation inhibitors) decreased the survival rate of hydrated seeds under freezing conditions, which indicated that energy metabolism was related to the freezing tolerance of hydrated seeds. The predicted interactions between PN and MDM2-like proteins of Lactuca indicated that LsMDM2-5 forms two potential hydrogen bonds with PN. Furthermore, based on AlphaFold predictions and yeast 2-hybrid results, MDM2-5 might interact directly with NADH2. The knockdown of MDM2-5 by RNAi caused a higher level of NADH2 and ATPsyn and a higher freezing tolerance of hydrated seeds. This indicated that MDM2 played negative roles in regulating ATP synthesis and freezing tolerance of hydrated seeds.

For many decades, seed germination data have been modelled by probit analysis. In particular, it is the basis of the seed viability equation used, in the first instance, to describe the decline in germination of seeds in storage, but then also the rate of the decline, depending on seed moisture content and the temperature of storage. The underlying assumption of a probit model is that the response follows a normal distribution, in this case, loss of the ability to germinate over time. Probit analysis also takes into account the binomial error associated with germination data. Many statistical packages have probit analysis as an option within the generalized linear modelling framework; here, we present code for applying probit analysis in the free software, R. Codes are provided for fitting a single survival curve, for a single seed lot stored in a constant storage environment; for fitting multiple survival curves and evaluating the effect of constraining parameters for the different seed lots; and lastly, to model the moisture relations of seed longevity. The code bases provided could also be used in pollen and fern/bryophyte spore longevity modelling.

Seeds rely on temperature to adjust their germination timing by modulating primary and secondary dormancy. The knowledge regarding an intraspecific variation in the germination responses to supra-optimal temperatures during imbibition within the Solanum lycopersicon species and its relation with pre- and post-harvest environments is limited. Here, we studied the impact of imbibition at 35°C in 17 genotypes selected from a multiparent advanced generation intercross (MAGIC) population. We discovered a high genetic variability in the germination responses to heat, leading to thermotolerance, thermoinhibition or thermodormancy with different depths. While thermodormancy appeared more profound than primary dormancy, there was no correlation between the deepness of primary and thermodormancy. Post-harvest treatments influenced considerably germination at supra-optimal temperatures. Dry storage beyond the apparent loss of primary dormancy led to an increased proportion of thermotolerant or thermoinhibited seeds at the expense of thermodormancy in a genotype-dependent manner, thereby revealing cryptic genetic variation. Prolonged cold imbibition also led to increased thermodormancy in genotypes that produced thermotolerant and thermoinhibited seeds. The thermal history before and after flowering influenced primary dormancy and the germination response to heat during imbibition in a genotype-dependent manner, with high temperatures leading to increased thermotolerance or thermoinhibition at the expense of thermodormancy, suggesting transgenerational plasticity despite the domestication of the species. The high potential of the MAGIC population for quantitative trait loci mapping and causal polymorphism identification will be helpful in deciphering the regulatory mechanisms that lead to the plasticity of thermoinhibition or thermodormancy, as well as their connection to the parental environment.

We have reviewed seed dormancy and germination in the Rubiaceae, the fourth-largest angiosperm family (in terms of species richness), in relation to ecology, life form, biogeography and phylogeny (subfamily/tribe). Life forms include trees, shrubs, vines and herbs, and tropical rainforest trees have the greatest number of tribes and species. The family has five kinds of embryos: investing, linear-full, linear-underdeveloped, spatulate and spatulate-underdeveloped, and seeds are non-dormant (ND) or have morphological (MD), morphophysiological (MPD) or physiological (PD) dormancy. Except for the occurrence of the investing embryo only in dry fruits of Dialypetalanthoideae, each kind of embryo is found in dry and fleshy fruits of Dialypetalanthodies and of Rubioideae. In tropical and temperate regions, there are species with ND seeds and others whose seeds have MD, MPD or PD. A complete seed dormancy profile (i.e. some species with ND seeds and others whose seeds have MD, MPD or PD) was found for tropical rainforest trees and shrubs and semi-evergreen rainforest shrubs. Dormancy-break occurs during cold or warm stratification or dry-afterripening, depending on the species. Some tropical species have long periods of dormancy-break/germination extending for 4–5 to 30–40 weeks. Soil seed banks are found in 5 and 15 tribes of Rubiaceae in tropical and temperate regions, respectively. With increased distance from the Equator, diversity of life forms and seed dormancy decreases, resulting in only herbs with PD at high latitudes. We conclude that the low species richness of Rubiaceae in temperate regions is not related to low diversity of seed dormancy/germination.