Temperature Regulation of Primary and Secondary Seed Dormancy in Rosa canina L.: Findings from Proteomic Analysis

A Multifaceted Evaluation Approach for Greek Native Neglected and Underutilized Forest Fruit Trees and Shrubs as Natural Sources of Antioxidants: Consolidating the Framework for Their Sustainable Agronomic Exploitation

Fruits from wild forest trees and shrubs represent a natural source of antioxidants against oxidative stress and a growing market for novel minor crops. This study presents a multifaceted approach which sets the basis for sustainable agronomic exploitation of selected Greek native germplasm of four traditional but neglected and underutilized forest fruit trees and shrubs, namely Amelanchier ovalis Medik., Cornus mas L., Rosa canina L., and Sambucus nigra L. The studied plant species are traditionally used in Greek ethnobotany but are currently neglected and underutilized in commercial terms, thus characterized as neglected and underutilized plant species (NUPs). The investigation includes new information on the evaluation of the ex situ cultivation of the Greek germplasm (three of the four focal NUPs), thus supplementing respective full datasets for their comparative evaluation based on four evaluation axes (documentation and molecular authentication of genotypes, phytochemical evaluation, asexual propagation via rooting of cuttings, and ex situ cultivation) after multi-year and multifaceted groundwork data previously acquired. Consecutively, the work includes feasibility and readiness timescale evaluation for the sustainable exploitation of each focal species based on existing literature and extant research experience. The feasibility for sustainable exploitation and readiness timescale evaluation results were very encouraging, showing high exploitation feasibility with an already achieved readiness timescale for R. canina and S. nigra, whereas C. mas and A. ovalis showed an achievable readiness in the short term. The comparative evaluation of the Greek native focal NUPs outlined the excellent potential of R. canina, S. nigra, and A. ovalis, and the high potential of C. mas. The results herein illustrate the very high fruit antioxidant potential (free radical scavenging activity) of all focal species, the diverse but effective asexual propagation capacity via cuttings at the species level, and summarize the results of a pilot cultivation trial set up in 2020 (still ongoing) outlining tree growth rates and the onset of fruit production among genotypes and species. Overall, the meta-analysis of previously published data in conjunction with new data generated herein may serve the sustainable exploitation of the studied NUPs.

Transcriptome and proteome analyses reveal the potential mechanism of seed dormancy release in Amomum tsaoko during warm stratification

BACKGROUND

In Amomum tsaoko breeding, the low germination rate is the major limitation for their large-scale reproduction. We found that warm stratification was an effective treatment to break the seed dormancy of A. tsaoko prior to sowing and could be an important component of improving breeding programs. The mechanism of seed dormancy release during warm stratification remains unclear. Therefore, we studied the differences between transcripts and proteomes at 0, 30, 60, and 90 days of warm stratification, to identify some regulatory genes and functional proteins that may cause seed dormancy release in A. tsaoko and reveal their regulatory mechanism.

RESULTS

RNA-seq was performed for the seed dormancy release process, and the number of differentially expressed genes (DEGs) was 3196 in three dormancy release periods. Using TMT-labelling quantitative proteome analysis, a total of 1414 proteins were defined as differentially expressed proteins (DEPs). Functional enrichment analyses revealed that the DEGs and DEPs were mainly involved in signal transduction pathways (MAPK signaling, hormone) and metabolism processes (cell wall, storage and energy reserves), suggesting that these differentially expressed genes and proteins are somehow involved in response to seed dormancy release process, including MAPK, PYR/PYL, PP2C, GID1, GH3, ARF, AUX/IAA, TPS, SPS, and SS. In addition, transcription factors ARF, bHLH, bZIP, MYB, SBP, and WRKY showed differential expression during the warm stratification stage, which may relate to dormancy release. Noteworthy, XTH, EXP, HSP and ASPG proteins may be involved in a complex network to regulate cell division and differentiation, chilling response and the seed germination status in A. tsaoko seed during warm stratification.

CONCLUSION

Our transcriptomic and proteomic analysis highlighted specific genes and proteins that warrant further study in fully grasping the precise molecular mechanisms that control the seed dormancy and germination of A. tsaoko. A hypothetical model of the genetic regulatory network provides a theoretical basis for overcoming the physiological dormancy in A. tsaoko in the future.

Seed Germination Ecology of Semiparasitic Weed Pedicularis kansuensis in Alpine Grasslands

The semiparasitic weed Pedicularis kansuensis Maxim. has rapidly spread in the alpine grasslands of northern China over the past twenty years and has caused serious ecological problems. In order to effectively halt the spread of this weed, a thorough understanding of the dormancy type and the seed-germination ecology of P. kansuensis is required. We have conducted a series of experiments to investigate the effects of plant growth regulators (gibberellin (GA₃) and strigolactone synthesis (GR24)), as well as different abiotic (temperature, light, cold stratification, and drought) and biotic (aqueous extracts of three native dominant plants) factors on the seed-germination characteristics of P. kansuensis. The seed-germination percentages ranged from 2% to 62% at all of the temperatures that were examined, with the highest occurring at 25/10 °C. The light conditions did not significantly affect the germination percentage. The seed germination was greatly improved after two to eight weeks of cold stratification. The seed germination decreased dramatically with an increasing polyethylene glycol (PEG-6000) concentration, from 55% to 0%, under 10% and 20% PEG-6000. The seed germination was improved at a proper concentration of GA₃, GR24, and the aqueous extracts of Festuca ovina L., Stipa purpurea L., and Leymus secalinus (Georgi) Tzvel. Furthermore, in the pot experiment, the seedling emergence of P. kansuensis was also improved by the cultivation of these three dominant grasses. These findings indicate that the dormancy type of P. kansuensis seeds is non-deep physiological dormancy, and such findings will help in paving the way for the creation of effective weed management strategies, based on a thorough knowledge of germination ecology.

Regulation of Seed Dormancy and Germination Mechanisms in a Changing Environment

Environmental conditions are the basis of plant reproduction and are the critical factors controlling seed dormancy and germination. Global climate change is currently affecting environmental conditions and changing the reproduction of plants from seeds. Disturbances in germination will cause disturbances in the diversity of plant communities. Models developed for climate change scenarios show that some species will face a significant decrease in suitable habitat area. Dormancy is an adaptive mechanism that affects the probability of survival of a species. The ability of seeds of many plant species to survive until dormancy recedes and meet the requirements for germination is an adaptive strategy that can act as a buffer against the negative effects of environmental heterogeneity. The influence of temperature and humidity on seed dormancy status underlines the need to understand how changing environmental conditions will affect seed germination patterns. Knowledge of these processes is important for understanding plant evolution and adaptation to changes in the habitat. The network of genes controlling seed dormancy under the influence of environmental conditions is not fully characterized. Integrating research techniques from different disciplines of biology could aid understanding of the mechanisms of the processes controlling seed germination. Transcriptomics, proteomics, epigenetics, and other fields provide researchers with new opportunities to understand the many processes of plant life. This paper focuses on presenting the adaptation mechanism of seed dormancy and germination to the various environments, with emphasis on their prospective roles in adaptation to the changing climate.