An Evolutionarily Conserved Receptor-like Kinases Signaling Module Controls Cell Wall Integrity During Tip Growth

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花粉管细胞结构与生长机制研究进展

花粉管的极性顶端生长是一个复杂的动力学过程,在高等植物有性生殖过程中起着重要的作用。花粉管的生长过程包括许多方面,其中最为重要的是花粉管细胞骨架动态和胞质运动。本文较全面地综述了花粉管的结构、细胞骨架、胞质运动、囊泡转运及循环、线粒体运动以及内质网和高尔基体之间囊泡运动等。     

肌动蛋白在丝瓜花粉管顶端生长中的作用

用非固定荧光标记的鬼笔环肽作为肌动蛋白探针观察并证明了丝瓜未萌发的花粉粒和不同生长时期花粉管中肌动蛋白纤丝的分布及其形态变化。又用细胞松弛素B（CB）、氯两嗪（CPZ）及N-乙酰马来酰胺（NEM）证明了丝瓜花粉管伸长与肌动蛋白既有密切的关系,也受Ca2 的调节。     

植物细胞壁中纤维素合成的研究进展

纤维素是植物细胞壁的主要成分,是植物细胞壁执行生理功能的基础,也是人类生产和生活中必不可少的一类物质。本文对纤维素合成、合成中所需要的酶以及纤维素沉积中微纤丝的作用等方面进行了综述和探讨, 并对纤维素合成的深入研究进行了展望。     

Cell Wall,Cytoskeleton, and Cell Expansion in Higher Plants

To accommodate two seemingly contradictory biological roles in plant physiology, providing both the rigid structural support of plant cells and the adjustable elasticity needed for cell expansion, the composition of the plant cell wall has evolved to become an intricate network of cellulosic, hemicellulosic, and pectic polysaccharides and protein. Due to its complexity, many aspects of the cell wall influence plant cell expansion, and many new and insightful observations and technologies are forthcoming. The biosynthesis of cell wall polymers and the roles of the variety of proteins involved in polysaccharide synthesis continue to be characterized. The interactions within the cell wall polymer network and the modification of these interactions provide insight into how the plant cell wall provides its dual function. The complex cell wall architecture is controlled and organized in part by the dynamic intracellular cytoskeleton and by diverse trafficking pathways of the cell wall polymers and cell wall-related machinery. Meanwhile, the cell wall is continually influenced by hormonal and integrity sensing stimuli that are perceived by the cell. These many processes cooperate to construct, maintain, and manipulate the intricate plant cell wall--an essential structure for the sustaining of the plant stature, growth, and life.     

KINKY POLLEN encodes a SABRE-like protein required for tip growth in Arabidopsis and conserved among eukaryotes

In higher plants, pollen tubes and root hairs share an ancient growth process named tip growth. We have isolated three allelic Arabidopsis mutant lines showing kinky-shaped pollen tubes and, when homozygous, showing shorter and thicker root hairs. The ultrastructure of pollen tubes in these kinky pollen (kip) mutants is similar to that of the wild type; however, time-lapse studies suggest that aberrant pollen tube shape is caused by periodic growth arrests alternated with phases of tube axis reorientation. The KIP gene encodes a protein of 2587 amino acids that is predicted to be targeted to the secretory pathway. KIP mRNA was detected in all organs investigated but was most abundant in pollen and roots. KIP has putative homologues in many eukaryotes, including mammals and yeast, and is similar to the Arabidopsis SABRE gene, whose mutation causes a dwarf phenotype. The phenotype of the kip/sab double mutant suggests related functions for both genes, however, the KIP protein is mostly required for tip-growth.     

Modeling pollen tube growth: Feeling the pressure to deliver testifiable predictions

The frequency and amplitude of oscillatory pollen tube growth can be altered by changing the osmotic value of the surrounding medium. This has motivated the proposition that the periodic change in growth velocity is caused by changes in turgor pressure. Using mathematical modeling we recently demonstrated that the oscillatory pollen tube growth does not require turgor to change but that this behavior can be explained with a mechanism that relies on changes in the mechanical properties of the cell wall which in turn are caused by temporal variations in the secretion of cell wall precursors. The model also explains why turgor and growth rate are correlated for oscillatory growth with long growth cycles while they seem uncorrelated for oscillatory growth with short growth cycles. The predictions made by the model are testifiable by experimental data and therefore represent an important step towards understanding the dynamics of the growth behavior in walled cells.     

一种植物细胞壁松驰蛋白:膨胀素

在植物细胞的生长过程中 ,多糖和蛋白质分泌到细胞壁里层 ,并形成具有一定机械强度的网络 ,这个网络是能伸展的 ,除非细胞停止生长。在细胞的生长过程中 ,一种细胞壁蛋白—膨胀素首次被鉴定出来具有使细胞壁的多糖网络疏松的能力 ,从而使膨压驱动的细胞扩大。膨胀素由两个多基因家族即α -膨胀素和 β -膨胀素多基因家族编码 ,每种基因的表达具有部位和细胞类型的特异性 ,但最新的研究也表明拟南芥中的膨胀素可以分为三个亚家族。越来越多的膨胀素基因从各种植物中鉴定出来 ,系统分析显示它们可能从一个共同的祖先基因进化而来。膨胀素的作用机理研究的还不是很清楚 ,但因为它们具有特别的功能 ,因此展现出良好的工业化应用前景。     

Stem Elongation and Cell Wall Proteins in Flowering Plants

Abstract: The growth of stems (hypocotyls, epicotyls) and stem-like organs (coleoptiles) in developing seedlings is largely due to the elongation of cells in the sub-apical region of the corresponding organ. According to the organismal concept of plant development, the thick outer epidermal wall, which can be traced back to the peripheral cell wall of the zygote, creates a sturdy organ sheath that determines the rate of stem elongation. The cells of the inner tissues are the products of secondary partitioning of one large protoplast; these turgid, thin-walled cells provide the driving force for organ growth. The structural differences between these types of cell walls are described (outer walls: thick, sturdy, helicoidal cellulose architecture; inner walls: thin, extensible, transversely-oriented cellulose microfibrils). On the basis of these facts, current models of cell wall loosening (and wall stiffening) are discussed with special reference to the expansin, enzymatic polymer remodelling and osmiophilic particle hypothesis. It is concluded that the exact biochemical mechanism(s) responsible for the coordinated yielding of the growth-controlling peripheral organ wall(s) have not yet been identified.     

Wall architecture with high porosity is established at the tip and maintained in growing pollen tubes of Nicotiana tabacum

A major question in pollen tube growth in planta remains: do the pollen tube walls form a barrier to interaction with the environment? Using cryo‐FESEM, we directly assessed the 3D construction and porosity of tobacco pollen tube walls. Fractured mature primary walls showed a 40–50 nm spaced lattice of continuous fibers interconnected by short rods in the primary wall. These observations agree with TEM observations of sectioned walls. In the secondary callose wall, for which no structure is visible using TEM, cryo‐FESEM also revealed a 50 nm lattice consisting of longer fibers, approximately 10–15 nm wide, with rod‐like, thinner interconnections at angles of approximately 90° with the longer fibers. Such architecture may reflect functional needs with respect to porosity and mechanical strength. The wall does not form a mechanical barrier to interaction with the environment and is gained at low cost. Cryo‐FESEM additionally revealed another special feature of the wall: the tubes were tiled with scales or rings that were highly conspicuous after pectin extraction with EDTA. These rings cause the typical banding patterns of pectin that are commonly seen in pollen tubes during oscillatory growth, as confirmed by staining with toluidine blue as well as by DIC microscopy. Growth analysis by VEC‐LM showed that the ring‐ or scale‐like structures of the primary wall consist of material deposited prior to the growth pulses. The alternating band pattern seen in the callose wall is probably imposed by constrictions resulting from the rings of the primary wall.     

植物原生质体的细胞壁再生

细胞壁作为植物细胞重要的组成部分,在决定细胞形状、维持机械支撑、吸收养分等方面发挥重要功能.因此,揭示植物细胞壁合成的调控机制具有重大的生物学意义.基于植物组织水平研究细胞壁的生物合成具有难以控制时间尺度、观察空间狭小等局限性.原生质体作为去除细胞壁的单个细胞是研究细胞壁再生的理想系统.在过去的几十年里报道了大量关于植...     

柿果实采后软化过程中细胞壁组分代谢和超微结构的变化

柿果实采后果胶酯酶活性迅速上升,其活性与果实硬度的下降呈明显的负相关。多聚半乳糖醛酸酶活性增加缓慢,但其活性与果实硬度的下降无明显相关性。β-半乳糖苷酶活性迅速增加,其活性与果实硬度的下降呈明显的负相关。纤维素酶活性呈逐渐上升趋势,与果实硬度的下降也呈明显的负相关。伴随着细胞壁水解酶活性的增加,果实原果胶和纤维素含量迅速下降,而水溶性果胶含量则迅速上升。柿果刚采收时细胞壁结构完整,3d后细胞壁中胶层基本被溶解,甚至初生壁也局部发生降解。     

植物细胞壁蛋白质组学研究进展

植物细胞壁蛋白质在细胞代谢和发育调控、细胞壁组分修饰、信号转导及胁迫响应等生物学事件中具有重要功能.最近,国内外学者开展了大量植物细胞壁蛋白质组学的研究工作,并取得了巨大进展.本文详述了细胞壁蛋白质的分类、提取、鉴定及生物信息学分析的最新进展,总结了植物细胞壁蛋白质组学的应用和面临的挑战,提出了植物细胞壁蛋白质组学研究的框架图,以期为植物细胞壁蛋白质组学的广泛研究提供借鉴.     

Cell axiality and polarity in plants — adding pieces to the puzzle

Plant cell polarity is important for cellular function and multicellular development. Classical physiological and cell biological analyses identified cues that orient cell polarity and suggested molecules that translate a cue into intracellular asymmetry. A range of proteins that either mark or are involved in the establishment of a (polar) axis are now available, as are many relevant mutants. These tools are likely to facilitate a dissection of the molecular mechanisms behind cell and organ polarity in the near future.     

Regulation of Bacterial,Yeast and Plant Polysaccharide Synthases: Implications for the Regulation of Pollen-tube Callose Synthase

从细菌、酵母及植物多糖合成酶的调控看花粉管胼胝质酶的调控 李惠娟1* Antony BACIC1 Steve M.READ2     

Pollen Cell Wall Patterns Form from Modulated Phases

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植物细胞壁介导的抗病性及其分子机制

本文简要介绍植物与病原菌在细胞壁层面上的相互作用,并从植物细胞对受侵过程中细胞壁损伤的感知、细胞壁损伤引起植物抗病信号途径的活化、植物细胞壁防卫反应的分子机制等方面重点概述植物细胞壁抗性及其分子机制。     

Cell wall deposition during morphogenesis in fucoid algae

Cell wall deposition was investigated during morphogenesis in zygotes of Pelvetia compressa (J. Agardh) De Toni. Young zygotes are spherical and wall is deposited uniformly, but at germination (about 10 h after fertilization) wall deposition becomes localized to the apex of the tip-growing rhizoid. Wall deposition was investigated before and after the initiation of tip growth by disrupting cytoskeleton, secretion or cellulose deposition; effects on wall strength and structure were examined. All three were involved in generating wall strength in both spherical and tip-growing zygotes, but their relative importance were different at the two developmental stages. Much of the wall strength in young zygotes was dependent on F-actin, whereas cellulose and a sulfated component, probably a fucan (F2), were most important in tip growing zygotes. Some treatments had contrasting effects at the two developmental stages; for example, disruption of F-actin or inhibition of secretion weakened walls in spherical zygotes but strengthened those in tip-growing zygotes. Transmission electron microscopic analysis showed that most treatments that altered wall strength induced modifications of internal wall structure. Received: 12 June 2000 / Accepted: 26 July 2000     

Root hair growth in Arabidopsis thaliana is directed by calcium and an endogenous polarity

Tip growth of plant cells has been suggested to be regulated by a tip-focused gradient in cytosolic calcium concentration ([Ca²⁺]_c). However, whether this gradient orients apical growth or follows the driving force for this process remains unknown. Using localized photoactivation of the caged calcium ionophore Br-A23187 we have been able to artificially generate an asymmetrical calcium influx across the root hair tip. This led to a change in the direction of tip growth towards the high point of the new [Ca²⁺]_c gradient. Such reorientation of growth was transient and there was a return to the original direction within 15 min. Root hairs forced to change the direction of their growth by placing a mechanical obstacle in their path stopped, reoriented growth to the side, and grew past the mechanical blockage. However, as soon as the growing tip had cleared the obstacle, growth returned to the original direction. Confocal ratio imaging revealed that a tip-focused [Ca²⁺]_c gradient was always centered at the site of active growth. When the root hair changed direction the gradient also reoriented, and when growth returned to the original direction, so did the [Ca²⁺]_c gradient. This normal direction of apical growth of Arabidopsis thaliana (L.) Heynh. root hairs was found to be at a fixed angle from the root of 85 ± 6.7 degrees. In contrast, Tradescantia virginiana (L.) pollen tubes that were induced to reorient by touch or localized activation of the caged ionophore, did not return to the original growth direction, but continued to elongate in their new orientation. These results suggest that the tip-focused [Ca²⁺]_c gradient is an important factor in localizing growth of the elongating root hair and pollen tube to the apex. However, it is not the primary determinant of the direction of elongation in root hairs, suggesting that other information from the root is acting to continuously reset the growth direction away from the root surface. Received: 22 April 1997 / Accepted: 14 May 1997