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Expansins and cell growth 总被引:10,自引:0,他引:10
Expansins are now generally accepted to be key regulators of wall extension during growth. Several alternative roles for expansins have emerged in which the emphasis of their action is on wall breakdown or softening in processes such as fruit ripening, pollination, germination and abscission. Expansins are commonly encoded by substantial gene families and have classically been divided into two subfamilies, referred to as alpha- and beta-expansins. Two further subfamilies have now been identified: gamma-expansins, which were first described in Arabidopsis, and delta-expansins, which were identified in rice and are absent from Arabidopsis. Both are truncated versions of alpha- and beta-expansins, with gamma-expansins representing the amino-terminal half of a mature expansin and delta-expansins the carboxy-terminal half of a beta-expansin. Functional roles for gamma- and delta-expansins have yet to be defined, although recent data indicate a signalling role for gamma-expansins. 相似文献
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Ortega JK 《Plant physiology》1985,79(1):318-320
The Growth Equation representing the relative rate of irreversible wall expansion is augmented with an elastic expansion component. Some of the utility of this augmented Growth Equation is demonstrated through selected applications. 相似文献
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Plant cell expansion: scaling the wall 总被引:5,自引:0,他引:5
The regulation of plant cell size and shape is poorly understood at the molecular level. Recently, two loci required for normal cell expansion in Arabidopsis were cloned. They both encode enzymes involved in the construction of the cell wall. These studies are the first promising examples of the use of Arabidopsis molecular genetics for the study of wall synthesis and assembly during plant cell elongation. 相似文献
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Decapitation of 30 mm oat coleoptiles, which are commonly usedfor growth tests, resulted in a decrease in their elastic extensibility(DE) but not in their plastic extensibility (DP). By auxin treatmentunder osmotic stress, old coleoptile (45 mm) cells showed noincrease in subsequent expansion in water, whereas RNA synthesisin these cells was stimulated just as in young ones. Auxin increasedthe DE of young coleoptile cell walls but not that of old ones.Significant increase of DE occurred in only 10 min, and themaximum level of DE was reached in 15 min of the auxin treatment.An antiauxin (2,4,6-trichlorophenoxyacetic acid), mitomycinC and cycloheximide inhibited auxin-induced increases in expansionand DE (or Rex, reversible extensibility) of young coleoptilecells. (Received July 23, 1968; ) 相似文献
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Expansins 总被引:4,自引:0,他引:4
Biochemical dissection of the "acid-growth" process of plant cell walls led to the isolation of a new class of wall loosening proteins, called expansins. These proteins affect the rheology of growing walls by permitting the microfibril matrix network to slide, thereby enabling the wall to expand. Molecular sequence analysis suggests that expansins might have a cryptic glycosyl transferase activity, but biochemical results suggest that expansins disrupt noncovalent bonding between microfibrils and the matrix. Recent discoveries of a new expansin family and gene expression in fruit meristems and cotton fibers have enlarged our view of the developmental functions of this group of wall loosening proteins. 相似文献
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植物激素在植物细胞壁扩展中的作用 总被引:3,自引:0,他引:3
细胞壁不仅是植物细胞结构的重要组成部分,而且控制着细胞的大小、形状和生长。细胞经有丝分裂后,原生质体吸水膨胀,细胞壁重塑,新生壁物质合成,纤维素定向沉积等引发细胞壁生长。在这些过程中,乙烯(ethylene,ET)、生长素(auxin)、赤霉素(gibberellin,GA)、油菜素甾醇(brassinosteroids,BR)等植物激素调控细胞壁生长相关酶类如纤维素合酶复合体(cellulose synthase A,CESA)、扩展素(expansin,EXP)、木葡聚糖内糖基转移酶/水解酶(xyloglucan endotran glucosylase/hydrolase,XET/XTH)的表达活性,进而调控细胞壁扩展,促使细胞壁的生长。 相似文献
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Morphogenesis of plant cells is tantamount to the shaping of the stiff cell wall that surrounds them. To this end, these cells integrate two concomitant processes: 1), deposition of new material into the existing wall, and 2), mechanical deformation of this material by the turgor pressure. However, due to uncertainty regarding the mechanisms that coordinate these processes, existing models typically adopt a limiting case in which either one or the other dictates morphogenesis. In this report, we formulate a simple mechanism in pollen tubes by which deposition causes turnover of cell wall cross-links, thereby facilitating mechanical deformation. Accordingly, deposition and mechanics are coupled and are both integral aspects of the morphogenetic process. Among the key experimental qualifications of this model are: its ability to precisely reproduce the morphologies of pollen tubes; its prediction of the growth oscillations exhibited by rapidly growing pollen tubes; and its prediction of the observed phase relationships between variables such as wall thickness, cell morphology, and growth rate within oscillatory cells. In short, the model captures the rich phenomenology of pollen tube morphogenesis and has implications for other plant cell types. 相似文献
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In azuki bean epicotyl segments, ethylN-phenylcarbamate, at the concentration where it brought about almost complete disappearance of wall microtubules, reversed
the gibberellin promotion and the kinetin inhibition of stem elongation. 相似文献
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Expansins in growing tomato leaves 总被引:18,自引:0,他引:18
An expansin-like protein from growing tomato leaves was identified by its ability to restore the 'acid-growth' response to heat-inactivated tomato walls and by its similarity to expansins from cucumber hypocotyls. Native walls from growing tomato leaves exhibit an endogenous acid-induced extension (creep) that resembles in various biochemical characteristics the acid-growth activity of cucumber hypocotyls. For example, the acid-growth activity is lost when the walls of tomato leaves are briefly heated and is largely restored by addition of a crude protein extract from the walls of growing leaves. Wall proteins from growing leaves enhance the stress relaxation spectrum of tomato walls in a fashion characteristic of cucumber expansins. HPLC fractionation of the crude wall protein from tomato leaves yielded an active fraction containing a major 27 kDa protein that cross-reacts with an antibody raised against cucumber expansin. The results show that tomato leafwalls possess at least one expansin that is responsible for the acid-growth property of leaves and indicate that cell wall extension in leaves shares an underlying protein mechanism common to cell wall expansion in stems. 相似文献
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Expansins and coleoptile elongation in wheat 总被引:2,自引:0,他引:2
Expansins are now generally accepted to be the key regulators of wall extension during plant growth. The aim of this study was to characterize expansins in wheat coleoptiles and determine their roles in regulating cell growth. Endogenous and reconstituted wall extension activities of wheat coleoptiles were measured. The identification of beta-expansins was confirmed on the basis of expansin activity, immunoblot analysis, and beta-expansin inhibition. Expansin activities of wheat coleoptiles were shown to be sensitive to pH and a number of exogenously applied factors, and their optimum pH range was found to be 4.0 to 4.5, close to that of alpha-expansins. They were induced by dithiothreitol, K(+), and Mg(2+), but inhibited by Zn(2+), Cu(2+), Al(3+), and Ca(2+), similar to those found in cucumber hypocotyls. An expansin antibody raised against TaEXPB23, a vegetative expansin of the beta-expansin family, greatly inhibited acid-induced extension of native wheat coleoptiles and only one protein band was recognized in Western blot experiments, suggesting that beta-expansins are the main members affecting cell wall extension of wheat coleoptiles. The growth of wheat coleoptiles was closely related to the activity and expression of expansins. In conclusion, our results suggest the presence of expansins in wheat coleoptiles, and it is possible that most of them are members of the beta-expansin family, but are not group 1 grass pollen allergens. The growth of wheat coleoptiles is intimately correlated with expansin expression, in particularly that of beta-expansins. 相似文献
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Expansins: ever-expanding numbers and functions 总被引:24,自引:0,他引:24
Expansins were first identified as cell-wall-loosening proteins that, at least in part, mediate pH-dependent extension of the plant cell wall and growth of the cell. More recently, it has been realized that expansins belong to two protein families, the alpha-and beta-expansins, and that they appear to be involved in regulating, besides cell expansion, a variety of plant processes, including morphogenesis, softening of fruits, and growth of the pollen tube of grasses through the stigma and the style. The Arabidopsis genome contains 26 alpha-expansin genes and the rice genome at least 26. There are more beta-expansin genes in monocots than in dicots, at least 14 in rice and five in Arabidopsis. Expansin genes are differentially regulated by environmental and hormonal signals, and hormonal regulatory elements have been found in their promoter regions. An analysis of exon/intron structure led to the hypothesis that alpha-and beta-expansins evolved from a common ancestral gene. 相似文献
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The distribution and activity of the cell wall-loosening protein expansin is correlated with internodal growth in deepwater rice (Oryza sativa L.). Acid-induced extension of native cell walls and reconstituted extension of boiled cell walls were confined to the growing region of the internode, i.e. to the intercalary meristem (IM) and the elongation zone. Immunolocalization by tissue printing and immunoblot analysis, using antibody against cucumber expansin 29 as a probe, confirmed that rice expansin occurred primarily in the IM and elongation zone. Rice expansin was localized mainly around the vascular bundles at the base of the IM and along the inner epidermal cell layer surrounding the internodal cavity. Submergence greatly promoted the growth of rice internodes, and cell walls of submerged internodes extended much more in response to acidification than did the cell walls of air-grown internodes. Susceptibility of cell walls to added expansin was also increased in submerged internodes, and analysis by immunoblotting showed that cell walls of submerged internodes contained more expansin than did cell walls of air-grown internodes. Based on these data, we propose that expansin is involved in mediating rapid internodal elongation in submerged deepwater rice internodes. 相似文献
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We investigated the function of the auxin-regulated cell wall gene DC 2.15, a member of a small gene family, present in Daucus carota (L.) and other plants. Cultured cells derived from carrot hypocotyls transformed by the DC 2.15 cDNA in antisense direction were ten-fold longer than wild-type cells, indicating a function of the corresponding protein in suppression of cell expansion. The analysis of carrot plants expressing the DC 2.15 gene in antisense direction showed that the corresponding protein and/or related proteins probably are involved in leaf and vascular bundle development. The antisense plants generally displayed a retarded growth phenotype and delayed greening in comparison to wild-type plants. The asymmetric architecture of the wild-type leaves was degenerated in the DC 2.15 antisense plants and the leaves showed a torsion within and along their major vein. The vascular bundles showed a lowered ratio of the phloem/xylem area in cross sections of the leaf middle vein whereas the bundle sheath and the cambium showed no obvious phenotype. Expression of a promoter-GUS construct was found primarily in vascular bundles of stems, leaves and in the nectar-producing flower discs. The observed pleiotropic antisense phenotype indicates, by loss of function, that one or several related cell wall proteins of this gene family are necessary to realize several complex developmental processes. 相似文献
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The results of studies of Micrasterias rotata (Grev.) Ralfs, M. thomasiana Archer (biradiate and uniradiate forms) and Closterium sp. using one- and two-dimensional vibrating probes show that transcellular ionic currents are detectable only around cells undergoing expansion of the primary cell wall (half-cell); current enters local regions of expansion and exits over both the rigid surface of the secondary wall and regions of the primary wall where hardening of the wall prevents further expansion. Current densities remain at steady levels until expansion stops with maturation of the primary wall, whereupon currents are no longer detectable. The temporal and spatial correlation between the currents and regions of wall expansion is particularly evident because morphogenesis of the half-cell is a determinate process. Measurements of inward currents ranged from 0.1 to 5.4 A · cm–2, and outward currents ranged from-0.05 to -1.5 A · cm–2 measured at 18 from the cell surface. The results of ion substitution and channel-blocker studies indicate that the currents may be carried at least in part by Ca2+, Cl–, H+ and K+ ions. The possible role of a Ca2+ influx during tip growth in desmids is discussed.This work was conducted at the National Vibrating Probe Facility, Marine Biological Laboratory, Woods Hole, Mass., USA. Dr. Lionel F. Jaffe, Director of the Facility, and Dr. Jeremy D. PickettHeaps, University of Colorado, Boulder, USA, provided valuable guidance and support, and gave unstinting encouragement during these studies. Dr. Franklin M. Harold provided support for the writing of this paper during C.L.T.'s postdoctoral year at the National Jewish Center for Immunology and Respiratory Research, Denver. Mr. Alan Shipley and Mr. Steve Dixon provided talented technical assistance. C.L.T. is grateful for support received from a National Institutes of Health Pre-doctoral Training Grant in the Department of Molecular, Cellular and Developmental Biology, University of Colorado. The work was supported by N.I.H. grants 5 P41 RR01395 and 3 P41 RR01395-02S1 (to L.F.J.), National Science Foundation grants No. BSR 82 14199 and PCM 83 09331 (to J.P.-H.), and No. DCB 86 18694 (to F.M.H.). 相似文献