Abstract
BackgroundCinnamomum migao is an endangered evergreen woody plant species endemic to China. Its fruit is used as a traditional medicine by the Miao nationality of China and has a high commercial value. However, its seed germination rate is extremely low under natural and artificial conditions. As the foundation of plant propagation, seed germination involves a series of physiological, cellular, and molecular changes; however, the molecular events and systematic changes occurring during C. migao seed germination remain unclear.ResultsIn this study, combined with the changes in physiological indexes and transcription levels, we revealed the regulation characteristics of cell structures, storage substances, and antioxidant capacity during seed germination. Electron microscopy analysis revealed that abundant smooth and full oil bodies were present in the cotyledons of the seeds. With seed germination, oil bodies and other substances gradually degraded to supply energy; this was consistent with the content of storage substances. In parallel to electron microscopy and physiological analyses, transcriptome analysis showed that 80–90 % of differentially expressed genes (DEGs) appeared after seed imbibition, reflecting important development and physiological changes. The unigenes involved in material metabolism (glycerolipid metabolism, fatty acid degradation, and starch and sucrose metabolism) and energy supply pathways (pentose phosphate pathway, glycolysis pathway, pyruvate metabolism, tricarboxylic acid cycle, and oxidative phosphorylation) were differentially expressed in the four germination stages. Among these DEGs, a small number of genes in the energy supply pathway at the initial stage of germination maintained high level of expression to maintain seed vigor and germination ability. Genes involved in lipid metabolism were firstly activated at a large scale in the LK (seed coat fissure) stage, and then genes involved in carbohydrates (CHO) metabolism were activated, which had their own species specificity.ConclusionsOur study revealed the transcriptional levels of genes and the sequence of their corresponding metabolic pathways during seed germination. The changes in cell structure and physiological indexes also confirmed these events. Our findings provide a foundation for determining the molecular mechanisms underlying seed germination.
Highlights
Cinnamomum migao is an endangered evergreen woody plant species endemic to China
Morphology and scanning electron microscopy observation during C. migao seed germination During the four germination stages of C. migao seeds (Fig. 1), structural changes were observed in the cotyledon cells under a scanning electron microscope (Fig. 2)
After the seeds absorbed water, the oil bodies were completely wrapped by the activated amorphous enzyme, the structure of the smooth oil bodies disappeared (Fig. 2 C and D), and some precipitates were observed on oil bodies, making their surfaces rough
Summary
Cinnamomum migao is an endangered evergreen woody plant species endemic to China. Its fruit is used as a traditional medicine by the Miao nationality of China and has a high commercial value. Its seed germination rate is extremely low under natural and artificial conditions. As the foundation of plant propagation, seed germination involves a series of physiological, cellular, and molecular changes; the molecular events and systematic changes occurring during C. migao seed germination remain unclear. W. Li is a species of the most important evergreen medicinal trees of the family Lauraceae. Owing to its special efficacy for angiocardiopathy and stomachache, C. migao has been commended as a famous and genuine medicinal material in Guizhou province. Excessive utilization of wild resources and the low germination rate of C. migao have resulted in the rare regeneration of individuals in the natural environment. Previous studies and our previous research field investigations have found that the number of the species has decreased [2, 3]
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