Ultrastructure of amyloplasts and intercellular transport of old and new scales inFritillaria ussuriensis

Amyloplast structure and intercellular transport in old and new scales ofFritillaria ussuriensis were observed by means of electron microscope. Most amyloplasts in old scales contained one starch grain, which was constructed by the layered deposition of starch around the hilum. Membrane systems and stroma of amyloplasts were pushed aside to form a shell surrounding the starch grain. In contrast, amyloplast shells in new scales contained a relatively light stroma and few internal membranes that were not organized into grana and stroma thylakoids. Active intercellular transport was observed in both new and old scales. Encytosis and exocytosis were common in the cell membrane and produced many vesicles containing numerous particles and filaments. These results lay the foundation for the further study on the mechanisms of growth and development in     

紫竹梅雄蕊毛发育过程中胞间连丝通透能力的动态变化

运用显微注射法将不同分子量的荧光分子探针注入紫竹梅雄蕊毛细胞中,在荧光显微镜下观察其通过胞间连丝转移情况。表明,开放花和花蕾Ⅳ期胞间连丝允许通过物质的分子量不超过１０００Ｄ,衰老花可允许ＦＩＴＣ－ｉｎｓｕｌｉｎＡ链（２９２１Ｄ）通过,而花蕾Ⅰ期可允许ＦＩＴＣ－ｄｅｘｔｒａｎ（４４００Ｄ）通过。说明胞间连丝允许通过物质的分子量极限不是固定不变的,它随组织、细胞的发育进程而改变。     

Plasmodesmata as a Modulator of Osmotic Water Fluxes in Plants

Solutions to some key problems in the relationships between the structure and functions of plasmodesmata, a component of the plant intercellular communication system, are proposed on the basis of the theory of osmotic flows through porous membranes. The theory accounts for structural characteristics of plasmodesmata, such as their dimension, shape, and length. It considers the steric and adsorption potentials of the solution–cell wall interaction and estimates water and solute (e.g., sucrose) flows under the sustained difference of osmotic pressures at the ends of plasmodesmata. The theory predicts that the water flow through plasmodesmata increases with the widening of the neck constriction and reaches its peak when its size is equal to the diameter of the solute molecule. The water-flow direction was found to depend on the opening of the annulus in neck constrictions at negative adsorption potentials of the plasmodesmata channel walls. Taking into account the presence of sphincters in the neck constrictions, our data suggest the role of plasmodesmata as a modulator of osmotic water fluxes in plants.     

To close or not to close: Plasmodesmata in defense

Cell death is a biological process that occurs during differentiation and maturation of certain cell types, during senescence, or as part of a defense mechanism against microbial pathogens. Intercellular coordination is thought to be necessary to restrict the spread of death signals, although little is known about how cell death is controlled at the tissue level. The recent characterization of a plasmodesmal protein, PDLP5, has revealed an important role for plasmodesmal control during salicylic acid-mediated cell death responses. Here, we discuss molecular factors that are potentially involved in PDLP5 expression, and explore possible signaling networks that PDLP5 interacts with during basal defense responses.     

破坏光敏色素A改变生长素反应因子8的表达谱

拟南芥生长素反应因子8（auxin response factor8,ARF8）受光诱导表达,涉及光信号转导。为阐明光信号通过光受体传递给ARF8的过程和机理,首先利用半定量RT-PCR分析发现,PhyA的突变促进幼苗中ARF8的表达,而PhyB、Cry1和Cry2的突变对ARF8的表达没有明显影响。进而,利用GUS染色以及半定量和定量RT-PCR方法,系统分析PhyA基因的突变对ARF8基因表达的影响。结果表明,在黑暗、白光和远红光条件下,PhyA突变均明显提高拟南芥（Arabidopsis thaliana）幼苗子叶和叶片中ARF8的表达水平,并且明显降低其在幼苗下胚轴、茎尖和根尖中的表达水平。上述结果说明,PhyA基因的突变组成型地改变了ARF8基因的表达谱。然而,ARF8的突变并未明显改变PhyA的表达。说明在远红光信号通路中,ARF8位于PhyA的下游。     

生长素与乙烯信号途径及其相互关系研究进展

长期的研究表明,生长素在调节植物生长发育的各种生理活动中起关键作用,但对它如何调控这些生理活动却缺乏系统和深入的了解。最近,细胞核内生长素信号途径的发现为揭示其作用机制带来了曙光。乙烯参与果实成熟及植物对逆境的反应等生理活动,其信号途径也已得到部分阐明。越来越多的证据表明,乙烯的作用与生长素对植物生长发育的调控之间有密切的联系。该文概述了生长素与乙烯信号途径的研究进展及其相互关系,讨论了生长素在植物三重反应中的作用;并对生长素与乙烯相互关系研究中存在的问题及研究前景进行了探讨。