Dendrobium Candidum Wall EX Lindl Protocorm Morphogenesis And Bioinformatics Analysis Of NAC Family

Dendrobium candidum Wall ex Lindl is an important Orchid plant, it has high medicinal and ornamental values. But human excavate it excessively and destruct of their habitats, and wild D. candidum has long reproductive cycle, low survival rate, so it becomes endangered species. In this paper, four aspects of D. candidum, which are how to save the pod and seed germination, morphological processes of protocorm happened and the processes of cellular occurred and bioinformatics analysis of NAC gene regulated protocorm primary meristem formation, are studied. In order to become an important means of protecting D. candidum germplasm, and provide a reference to breeding work. The main results are described as follows:1. Without cryopreservation experiments, the optimal way of pods storage was surface disinfection first then putted in 4℃ vacuum environment. It can save 4 months, and seed germination rate was more than 90%.2. Dendrobium normal seed colour was yellow-green, both micro-tip ends of the seed was spindle-shaped, dozens of cells became oval-shaped embryo in the middle of seed coat. Testa was a layer of elongated parenchyma cells, it was transparent with no content. The thick ring had a certain deflection angle. Spindle-shaped testa had different ends, the fine tip end and the obtuse end. The average length of embryo was 180μm, width was 120μm. Testa length was 400μm, width was 120μm. The length ratio of embryo and seed was 22.2%.3.Dendrobium seed in the process of non-symbiotic culture, seeds broke through testa about 25d. Protocorm top would have some green pigment accumulation there, since the bottom of the embryo and scattering absorption hair appeared. A week later, it developed into a round ball. Notch appeared on the top central region of the protocorm about 40d. Then protuberance appeared on the notch, it would fill the notch with protuberance. Protuberance continued to develop into the cotyledon, then formed a small ditch in the cotyledon flank. Lasted a month it gradually developed into ellipsoidal. And a leaf grew from cotyledons contralateral ditch. It looked like dumbbell about 80d. The protocorm had gradual degradation at the bottom, and roots came in a week. Finally, the formation of seedlings lasted totaling around 110d.4. The trend aspect ratio of the protocorm was affected of the growth rate of cell division protocorm in longitudinal direction and latitudinal direction. After 45d, it increased mainly the length of protocorm. Seed had strongest vigor in mid-pods. When a single vaccination required the number of seed pods was far below the seed pods content, people should better choose mid-pod seeds. No significant effect of light occurred in the ball of the previous period and the protocorm. Dark culture only delayed the process and increased the length of the protocorm.5. We used protocorm of different form-stages and conventional paraffin sectioning techniques to research cellular processes when seed became protocorm. It had four successive developmental stages feature. The first was embryo stage (only meristem cell divided), the second was the protocorm formation stage (parenchyma cells also started to split), then it came protocorm maturity and protocorm degradation. Protocorm maturity divided into the original meristem formation, shoot apical meristem (SAM) formation, leaf primordia or vascular system formation and the formation of the root apical meristem (RAM).6.Analyzing amino acid sequence and the genomic sequence in NAM domain of NAC transcription factor of Arabidopsis thaliana, Oryza sativa, Zea mays, Glycine max and Medicago truncatula, the NAC family had been divided into some group according to the amino acid sequence features.