Changes in oxidative patterns during dormancy break by warm and cold stratification in seeds of an edible fruit tree

Amomum tsaoko DRM1 regulate seed germination and improve heat tolerance in Arabidopsis

Seed dormancy and germination are critical to medicinal plant reproduction. Dormancy-associated gene (DRM1) has been involved in the regulation of dormancy in Arabidopsis meristematic tissues or organs. However, research on molecular functions and regulations of DRM1 in Amomum tsaoko, an important medicinal plant, is rare. In this study, the DRM1 was isolated from embryos of A. tsaoko, and the results of protein subcellular localization in Arabidopsis protoplast indicated that DRM1 was mainly nucleus and cytoplasm. Expression analysis showed that DRM1 especially exhibited the highest transcript level in dormant seed and short-time stratification while displaying a high response of hormone and abiotic stress. Further investigation showed that ectopic expression of DRM1 in Arabidopsis exhibited delayed seed germination and germination capability to high temperatures. Additionally, DRM1 transgenic Arabidopsis exhibited increased tolerance to heat stress by enhancing antioxidative capacities and regulating stress-associated genes (AtHsp25.3-P, AtHsp18.2-CI, AtHsp70B, AtHsp101, AtGolS1, AtMBF1c, AtHsfA2, AtHsfB1 and AtHsfB2). Overall, our results reveal the role of DRM1 in seed germination and abiotic stress response.

RNA-seq study reveals the signaling and carbohydrate metabolism regulators involved in dormancy release by warm stratification in Paris polyphylla var. yunnanensis

Long-term seed dormancy of Paris polyphylla var. yunnanensis limits its large-scale artificial cultivation. It is crucial to understand the regulatory genes involving in dormancy release for artificial cultivation in this species. In this study, seed dormancy of Paris polyphylla var. yunnanensis was effectively released by warm stratification (20°C) for 90 days. The freshly harvested seeds (dormant) and stratified seeds (non-dormant) were used to sequence, and approximately 147 million clean reads and 28,083 annotated unigenes were detected. In which, a total of 10,937 differentially expressed genes (DEGs) were identified between dormant and non-dormant seeds. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) classification revealed that the majority unigenes involved in signaling transduction and carbohydrate metabolism. Of them, the signaling transduction-related DEGs were mainly hormones-, reactive oxygen species (ROS)-, and transcription factor (TF)-related genes. The largest number of signaling transduction-related DEGs were auxin-responsive genes (SAUR, AUX/IAA, and ARF) and AP2-like ethylene-responsive transcription factor (ERF/AP2). Moreover, at least 29 DEGs such as α-amylase (AMY), β-glucosidase (Bglb/Bglu/Bglx), and endoglucanase (Glu) were identified involving in carbohydrate metabolism. These identified genes provide a valuable resource to investigate the molecular basis of dormancy release in Paris polyphylla var. yunnanensis.

Nitric Oxide in Seed Biology

Nitric oxide (NO) has been recognized as a gasotransmitter in the mainstream of plant research since the beginning of the 21st century. It is produced in plant tissue and the environment. It influences plant physiology during every ontogenetic stage from seed germination to plant senescence. In this review, we demonstrate the increased interest in NO as a regulatory molecule in combination with other signalling molecules and phytohormones in the information network of plant cells. This work is a summary of the current knowledge on NO action in seeds, starting from seed pretreatment techniques applied to increase seed quality. We describe mode of action of NO in the regulation of seed dormancy, germination, and aging. During each stage of seed physiology, NO appears to act as a key agent with a predominantly beneficial effect.

Cool-Warm Temperature Stratification and Simulated Bird Digestion Optimize Removal of Dormancy in Rosa rugosa Seeds

Rosa rugosa Thunb. has been explored multi-function in medicinal, edible, cosmetic, ornamental and ecological etc. However, R. rugosa natural populations have recently declined substantially in China, besides of global climate change, this species also has the defect of limiting the reproduction of itself such as the hard-to-release seed dormancy. In this study, only 30% of R. rugosa seeds were viable, and the others were incompletely developed or diseased seeds. Without stratification, morphologically complete viable seeds imbibed water but those seeds could not germinate even after seed husk removal under suitable condition to exhibit a physiological dormancy. After cold (4°C) and warm (18 ± 2°C) stratification, macromolecular substances containing carbon or nitrogen accumulated, and respiration, antioxidant enzyme activity, and gibberellin (GA₃) /abscisic acid (ABA) and auxin (IAA)/ABA ratios increased significantly in seeds. Water absorption also increased as endocarps softened. Thus, physiological dormancy of seed was broken. Although warm and cold stratification increased separation between endocarp and embryo, the endocarp binding force was removed insufficiently, because only 10.20% of seeds germinated. Therefore, stratified seeds were treated with simulated bird digestion. Then, folds and cracks in loosened endocarps increased permeability, and water absorption rate increased to 64.43% compare to 21.14% in cold and warm stratification treatment. With simulated digestion, 24.20% of radicles broke through the endocarp with plumules and cambiums to develop into seedlings. Thus, the seed dormancy type of R. rugosa is physiological as seeds imbibed water and possessed fully developed embryos with a low growth potential in combination with a mechanical constraint from the endocarp. Cold stratification helped remove physiological dormancy, and additional warm stratification accelerated the process. The optimal stratification treatment was 4°C for 45 days followed by 18 ± 2°C for 15 days. After warm and cold stratification, simulated bird digestion broke the mechanical constraint from the seed covering layers. Based on this research, production of R. rugosa seedlings can be greatly increased to help protect the species from further declines.