SUMO化修饰系统在哺乳动物胚胎发育及器官发生中的作用

小分子泛素相关修饰物蛋白（small ubiquitin-related modifier protein,SUMO）化修饰是一种广泛存在的蛋白质翻译后修饰形式,存在于动物多个生理和病理过程中,并涉及复杂的信号通路调节过程,是细胞对应激反应的重要调节机制,并且越来越多的研究表明,SUMO化修饰在哺乳动物胚胎发育及器官发生过程中发挥重要作用。在胎儿发育过程中,SUMO化对于器官的形成及发育起着至关重要的作用。SUMO化途径的各组成成分（UBC9、SUMO1~3、PIAS、SENP1~7）在胚胎发育过程中协调胚泡与子宫间的对话、心脏发育以及颅面发育中都发挥着重要作用。在发育过程中SUMO化修饰一旦失调,则可能导致胚胎植入前缺陷、胚胎发育缺陷以及胚胎致死。本综述总结了SUMO化修饰的分子机制,以及SUMO化途径各个组成成分（SUMO、UBC9、PIAS、SENPs）在早期胚胎发育及后续器官发生中功能的最新进展,以望为后续的研究提供借鉴。     

Avian fissura prima: differential accumulation of extracellular matrix at a fold

Extracellular matrix components that flank the fissura prima, a primary surface infolding of the cerebellum in birds and mammals, were examined in the embryonic chick using light and transmission electron microscopy. Cerebella dissected from Day 10 embryos were perfused with a paraformaldehyde-glutaraldehyde-tannic acid primary fixative and sectioned in the sagittal plane through the mid-vermis. Ultrastructural analysis revealed a distinct, continuous basal lamina separating the organ parenchyma (epithelia) from pia mater (mesenchyme) at the fissure surface (arbitrarily labeled; fissure floor, folia wall, and folia apex). The basal lamina was significantly thicker (P < 0.001) at the fissure floor compared to that found at the folia wall, which was significantly thicker (P < 0.001) than that observed at the folia apex. Folds in the basal lamina were observed exclusively at the fissure floor. Surface-associated collagen fibrils were distributed in an aligned, relatively dense manner at the fissure floor, compared with fibrils observed in various orientations and widely separated or absent at the folia wall and folia apex. Metachromasia was more pronounced in the fissure floor than in either the folia wall or folia apex in methylene blue-stained tissue sections. Together, the thicker, folded basal lamina and densely aligned collagen fibrils at the fissure floor provide a chemical rationale for this color change. These findings suggest that the differential accumulation of extracellular matrix at the fissura prima is positioned to play a structural and/or biochemical role in the maintenance of this fold.     

Light quality influences adventitious shoot production from cotyledon explants of lettuce (<Emphasis Type="Italic">Lactuca sativa</Emphasis> L.)

Summary The influence of light quality on competence and determination for organogenesis was investigated using lettuce cotyledon explants. Lettuce seedlings from four genotypes were germinated in the dark or under white, red, or blue light. Cotyledon explants were excised and cultured on a shoot-inducing medium for 28 d under white light. Germination in the dark reduced shoot numbers, suggesting that light improves the competence of explants for organogenesis. When explants from seedlings germinated under white light were cultured under different light qualities, blue was found to inhibit shoot production while red light either promoted production or had no effect on shoot number compared to controls. Treatment with blue plus red light failed to overcome the inhibition by blue light. To ascertain the temporal responses of explants to light quality, they were cultured under red or blue light prior to transfer to the alternate treatment. Exposure to blue light within 7 d of excision permanently reduced explant competence for organogenesis. Exposure after this time had a minimal effect. These results suggest that both phytochrome and cryptochrome can regulate shoot production from lettuce cotyledon explants and blue light can only inhibit organogenesis, in lettuce, during a relatively small developmental window.     

In vitro propagation of loblolly pine via direct somatic organogenesis from mature cotyledons and hypocotyls

A high-efficiency two-step culture procedure for direct somaticorganogenesis in loblolly pine (Pinus taeda L.) resulting inthe formation of multiple shoot structures induced on cotyledons andhypocotyls of mature zygotic embryos is described. Mature zygoticembryos of eight genotypes of loblolly pine were used as explants toinduce direct somatic organogenesis with this two-step culture method,involving the induction and the differentiation of direct adventitiousshoots. After mature zygotic embryos of eight genotypes of loblolly pinewere cultured on induction medium containing 2,4-dichlorophenoxyaceticacid (2,4-D) or -naphthaleneacetic acid (NAA), 6-benzyladenine(BA), and kinetin for 2–3 weeks, embryos were transferred todifferentiation medium. Adventitious shoot regeneration via directsomatic organogenesis with the frequency of 8.7–27.8% wasobtained from mature zygotic embryo cultures of the genotypes tested.The highest mean number of 32.6 adventitious shoots per mature zygoticembryo was produced from genotype La. The tissue culture protocol of invitro shoot regeneration via direct somatic embryogenesis was optimizedafter examining the periods of the induction culture, chillingtreatment, glutamine concentration, and basic medium levels. Rooting wasachieved on TE medium supplemented with 0.5 mg/l indole-3-butyric acid(IBA), 0.5 mg/l gibberellic acid (GA₃), and 1 mg/l6-benzyladenine (BA), and regenerated plantlets were established insoil. These results suggested that adventitious shoot regeneration viadirect somatic organogenesis could be useful for clonal micropropagationof some genotypes of loblolly pine and for establishing a transformationsystem of this coniferous species.     

Extracellular matrix remodeling and metalloproteinase involvement during intestine regeneration in the sea cucumber Holothuria glaberrima

The sea cucumber, Holothuria glaberrima, has the capacity to regenerate its internal organs. Intestinal regeneration is accomplished by the thickening of the mesenteric border and the invasion of this thickening by mucosal epithelium from the esophagus and the cloaca. Extracellular matrix (ECM) remodeling has been associated with morphogenetic events during embryonic development and regeneration. We have used immunohistochemical techniques against ECM components to show that differential changes occur in the ECM during early regeneration. Labeling of fibrous collagenous components and muscle-related laminin disappear from the regenerating intestine and mesentery, while fibronectin labeling and 4G7 (an echinoderm ECM component) are continuously present. Western blots confirm a decrease in fibrous collagen content during the first 2 weeks of regeneration. We have also identified five 1,10-phenanthroline-sensitive bands in collagen gelatin zymographs. The gelatinolytic activities of these bands are enhanced during early stages of regeneration, suggesting that the metalloprotease activity is associated with ECM remodeling. Inhibition of MMPs in vivo with 1,10-phenanthroline, p-aminobenzoyl-Gly-Pro-D-Leu-D-Ala hydroxamate or N-CBZ-Pro-Leu-Gly hydroxamate produces a reversible inhibition of intestinal regeneration and ECM remodeling. Our results show that significant changes in ECM content occur during intestine regeneration in the sea cucumber and that the onset of these changes is correlated to the proteolytic activities of MMPs.     

Periods of organogenesis in shoots of Nothofagus dombeyi (Mirb.) oersted (Nothofagaceae)

The organogenetic cycle of main-branch shoots of Nothofagus dombeyi (Nothofagaceae) was studied. Twelve samples of 52-59 parent shoots were collected from a roadside population between September 1999 and October 2000. Variations over time in the number of nodes of terminal and axillary buds, and the length, diameter and number of leaves of shoots derived from these buds (sibling shoots) were analysed. The number of nodes of buds developed by parent shoots was compared with the number of nodes of buds developed, I year later, by sibling shoots. The length, diameter and number of leaves of sibling shoots increased from October 1999 to February 2000 in those shoots with a terminal bud. However, extension of most sibling shoots, including the first five most distal leaf primordia, ceased before February due to abscission of the shoot apex. Axillary buds located most distally on a shoot had more nodes than both terminal buds and more proximal axillary buds. The longest shoots included a preformed part and a neoformed part. The organogenetic event which initiated the neoformed organs continued until early autumn, giving rise to the following year's preformation. The absence of cataphylls in terminal buds could indicate a low intensity of shoot rest. The naked terminal bud of Nothofagus spp. could be interpreted as a structure less specialized than the scaled bud found in genera of Fagaceae and Betulaceae.     

Direct regeneration of Drosera from leaf explants and shoot tips

An efficient protocol for the micropropagation of Drosera anglica, D. binata and D. cuneifolia is described. Proliferation was obtained from leaf segments and shoot tips, which served as initial explants. The regeneration capacity of explants was influenced by factors such as nutrient media, concentrations of growth regulators and the type of medium (liquid or solid). The highest number of plants regenerating from D. binata explants was obtained on the growth regulator-free Vacin and Went medium. In the case of D. anglica the highest proliferation rate was obtained on the Fast medium supplemented with 0.05 M 6-benzyladenine (BA) and 0.005 M -naphthaleneacetic acid (NAA), whereas for D. cuneifolia the optimal regeneration medium proved to be 1/2 MS with the growth regulator supplementation estimated at 0.2 M BA and 0.2 M NAA. Liquid media significantly increased the regeneration potential of D. anglica and D. binata explants.     

Plant regeneration from embryo-derived callus of oil palm – the effect of exogenous polyamines

Regeneration in oil palm was achieved through somatic embryogenesis/organogenesis from embryo-derived callus. Callus was induced from mature embryos of the cross 281 (D)×18 (P) on modified MS medium supplemented with 2,4-D (113.12 M) and 2-iP (14.76 M). The embryogenic calluses obtained were transferred to Blaydes medium supplemented with 2,4-D (0.045 M) and one of the following growth regulators: TDZ (4.54 M), zeatin riboside (2.85 M), putrescine (1 mM) and spermine (100 M). Secondary somatic embryogenesis was found to occur in media supplemented with polyamines. The efficiency of formation of somatic embryos, secondary somatic embryos and shoot meristemoids were significantly higher in putrescine containing medium. Histological studies were also undertaken.