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1.
Laccase, EC 1.10.3.2 or p-diphenol:dioxygen oxidoreductase, has been proposed to be involved in lignin synthesis in plants based on its in vitro enzymatic activity and a close correlation with the lignification process in plants. Despite many years of research, genetic evidence for the role of laccase in lignin synthesis is still missing. By screening mutants available for the annotated laccase gene family in Arabidopsis, we identified two mutants for a single laccase gene, AtLAC15 (At5g48100) with a pale brown or yellow seed coat which resembled the transparent testa (tt) mutant phenotype. A chemical component analysis revealed that the mutant seeds had nearly a 30% decrease in extractable lignin content and a 59% increase in soluble proanthocyanidin or condensed tannin compared with wild-type seeds. In an in vitro enzyme assay, the developing mutant seeds showed a significant reduction in polymerization activity of coniferyl alcohol in the absence of H2O2. Among the dimers formed in the in vitro assay using developing wild-type seeds, 23% of the linkages were β-O-4 which resembles the major linkages formed in native lignin. The evidence strongly supports that AtLAC15 is involved in lignin synthesis in plants. To our knowledge, this is the first genetic evidence for the role of laccase in lignin synthesis. Changes in seed coat permeability, seed germination and root elongation were also observed in the mutant.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at . 相似文献
2.
Arabidopsis COGWHEEL1 links light perception and gibberellins with seed tolerance to deterioration 总被引:1,自引:0,他引:1
Eduardo Bueso Jesús Muñoz‐Bertomeu Francisco Campos Cándido Martínez Carlos Tello Irene Martínez‐Almonacid Patricia Ballester Miguel Simón‐Moya Veronique Brunaud Lynne Yenush Cristina Ferrándiz Ramón Serrano 《The Plant journal : for cell and molecular biology》2016,87(6):583-596
3.
Deposition and localization of lipid polyester in developing seeds of Brassica napus and Arabidopsis thaliana 总被引:2,自引:0,他引:2
Molina I Ohlrogge JB Pollard M 《The Plant journal : for cell and molecular biology》2008,53(3):437-449
Mature seeds of Arabidopsis thaliana and Brassica napus contain complex mixtures of aliphatic monomers derived from non-extractable lipid polyesters. Most of the monomers are deposited in the seed coat, and their compositions suggest the presence of both cutin and suberin layers. The location of these polyesters within the seed coat, and their contributions to permeability of the seed coat and other functional properties are unknown. Polyester deposition was followed over Brassica seed development and distinct temporal patterns of monomer accumulation were observed. Octadecadiene-1,18-dioate, the major leaf cutin monomer, was transiently deposited. In contrast, the saturated dicarboxylates maintained a constant level during seed desiccation, whereas the fatty alcohols and saturated omega-hydroxy fatty acids continually increased. Dissection and analysis of Brassica seed coats showed that suberization is not specific to the chalaza. Analysis of the Arabidopsis ap2-7 mutant suggested that suberin monomers are preferentially associated with the outer integument. Several Arabidopsis knockout mutant lines for genes involved in polyester biosynthesis (att1, fatB and gpat5) were examined for seed monomer load and composition. The variance in polyester monomers of these mutants is correlated with dye penetration assays. Furthermore, stable transgenic plants expressing promoter::YFP fusions showed ATT1 promoter activity in the inner integument, whereas GPAT5 promoter is active in the outer integument. Together, the Arabidopsis data indicated that there is a suberized layer associated with the outer integument and a cutin-like polyester layer associated with the inner seed coat. 相似文献
4.
Seed-coat dormancy in Grevillea linearifolia: little change in permeability to an apoplastic tracer after treatment with smoke and heat 总被引:1,自引:0,他引:1
BACKGROUND AND AIMS: Seeds of Grevillea linearifolia germinate following fire, and have seed-coat dormancy broken by smoke and heat shock. Smoke breaks seed coat dormancy in Emmenanthe penduliflora by altering the permeability of the seed coat to an internal germination inhibitor, which subsequently escapes. This model was tested for in G. linearifolia by investigating the permeability of the seed coat to diffusion of high-molecular-weight compounds, and whether this changed after exposure to fire cues. METHODS: Germination response of the seeds to heat shock, smoke or heat + smoke was tested. Penetration of Lucifer Yellow dye into intact seeds was examined after 24 and 48 h of exposure, and penetration of the dye from the inside of the seed coat outwards was examined after 24 h. Histochemical staining with Nile Red and Acridine Orange was used to locate cuticles, suberin and lignin. KEY RESULTS: Twenty-three per cent of untreated seeds germinated; heat shock and smoke increased germination additively up to approx. 80 % for both cues combined. Lucifer Yellow did not penetrate fully through the seed coat of untreated seeds, whether diffusing inwards or outwards. Three barriers to diffusion were identified. Treatment with heat or smoke slightly increased penetration of the dye, but did not completely remove the barriers. Suberin was identified in secondary walls of exotestal and mesotestal cells, and was absent from primary cell walls. Movement of Lucifer Yellow occurred through the middle lamella and primary cell wall of suberized cells; movement of the dye was impeded where suberin was absent. CONCLUSIONS: Fire cues did not significantly decrease barriers to diffusion of high-molecular-weight compounds in the seed coat of Grevillea, and must be breaking dormancy by another mechanism. 相似文献
5.
Effects of APETALA2 on embryo, endosperm, and seed coat development determine seed size in Arabidopsis 总被引:2,自引:0,他引:2
Masa-aki Ohto Sandra K. Floyd Robert L. Fischer Robert B. Goldberg John J. Harada 《Sexual plant reproduction》2009,22(4):277-289
Arabidopsis APETALA2 (AP2) controls seed mass maternally, with ap2 mutants producing larger seeds than wild type. Here, we show that AP2 influences development of the three major seed compartments:
embryo, endosperm, and seed coat. AP2 appears to have a significant effect on endosperm development. ap2 mutant seeds undergo an extended period of rapid endosperm growth early in development relative to wild type. This early
expanded growth period in ap2 seeds is associated with delayed endosperm cellularization and overgrowth of the endosperm central vacuole. The subsequent
period of moderate endosperm growth is also extended in ap2 seeds largely due to persistent cell divisions at the endosperm periphery. The effect of AP2 on endosperm development is
mediated by different mechanisms than parent-of-origin effects on seed size observed in interploidy crosses. Seed coat development
is affected; integument cells of ap2 mutants are more elongated than wild type. We conclude that endosperm overgrowth and/or integument cell elongation create
a larger postfertilization embryo sac into which the ap2 embryo can grow. Morphological development of the embryo is initially delayed in ap2 compared with wild-type seeds, but ap2 embryos become larger than wild type after the bent-cotyledon stage of development. ap2 embryos are able to fill the enlarged postfertilization embryo sac, because they undergo extended periods of cell proliferation
and seed filling. We discuss potential mechanisms by which maternally acting AP2 influences development of the zygotic embryo
and endosperm to repress seed size. 相似文献
6.
7.
Emile J. M. Clerkx Hetty Blankestijn-De Vries Gerda J. Ruys Steven P. C. Groot Maarten Koornneef 《Physiologia plantarum》2004,121(3):448-461
Seeds gradually lose their viability during dry storage. The damage that occurs at the biochemical level can alter the seed physiological status and is affected by the storage conditions of the seeds. Although these environmental conditions controlling loss of viability have been investigated frequently, little information is available on the genetics of seed longevity. Using Arabidopsis mutants in defined developmental or biochemical pathways such as those affected in seed coat composition, seed dormancy, hormone function and control of oxidative stress, we tried to gain insight into the genes and mechanisms controlling viability of stored seeds. Mutations like abscisic acid insensitive3 ( abi3 ) as well as abscisic acid deficient1 ( aba1 ) show reduced longevity, which may be partially related to the seed dormancy phenotype of these mutants. Mutants with seed coat alterations, especially aberrant tests shape ( ats ), showed a stronger reduction in germination percentage after storage, indicating the importance of a 'functional' seed coat for seed longevity. A specific emphasis was placed on mutants affected in dealing with Reactive Oxygen Species (ROS). Because several pathways are involved in protection against ROS and because gene redundancy is a common feature in Arabidopsis , 'double' mutants were generated. These 'double' mutants and the corresponding single mutants were subjected to a controlled deterioration test (CDT) and a germination assay on hydrogen peroxide (H2 O2 ) after prolonged storage at two relative humidities. CDT and germination on H2 O2 affected all genotypes, although it appears that other effects like genetic background are more important than the deficiencies in the ROS scavenging pathway. Explanations for this limited effect of mutations affecting ROS scavenging are discussed. 相似文献
8.
9.
Fang Chen Yuki Tobimatsu Lisa Jackson Jin Nakashima John Ralph Richard A. Dixon 《The Plant journal : for cell and molecular biology》2013,73(2):201-211
We have recently described a hitherto unsuspected catechyl lignin polymer (C‐lignin) in the seed coats of Vanilla orchid and in cacti of one genus, Melocactus (Chen et al., Proc. Natl. Acad. Sci. USA. 2012, 109, 1772‐1777.). We have now determined the lignin types in the seed coats of 130 different cactus species. Lignin in the vegetative tissues of cacti is of the normal guaiacyl/syringyl (G/S) type, but members of most genera within the subfamily Cactoidae possess seed coat lignin of the novel C‐type only, which we show is a homopolymer formed by endwise β–O–4‐coupling of caffeyl alcohol monomers onto the growing polymer resulting in benzodioxane units. However, the species examined within the genera Coryphantha, Cumarinia, Escobaria and Mammillaria (Cactoideae) mostly had normal G/S lignin in their seeds, as did all six species in the subfamily Opuntioidae that were examined. Seed coat lignin composition is still evolving in the Cactaceae, as seeds of one Mammillaria species (M. lasiacantha) possess only C‐lignin, three Escobaria species (E. dasyacantha, E. lloydii and E. zilziana) contain an unusual lignin composed of 5‐hydroxyguaiacyl units, the first report of such a polymer that occurs naturally in plants, and seeds of some species contain no lignin at all. We discuss the implications of these findings for the mechanisms that underlie the biosynthesis of these newly discovered lignin types. 相似文献
10.
In this work, we investigated the inhibitory effects of water-soluble phenolic compounds (WSPCs) in the coat of after-ripening
wheat (Triticum aestivum L.) seeds on the processes of germination and peroxidase reactivation. Wheat bran has a WSPC content of 862.5 μg gallic acid
equivalent g−1 dry weight. When seeds were incubated in the water extract of bran, germination, peroxidase reactivation, and coleoptile
and radicle growth were suppressed in a WSPC concentration-dependent manner. The inhibitory effects were significantly ameliorated
by removing WSPCs from bran extract by treating with 1% insoluble polyvinylpolypyrrolidone. Pretreatment of seeds with 0.1%
H2O2 reduced the WSPC content in the coat, which was confirmed using Fourier transform infrared microspectroscopy. With H2O2 pretreatment, seed germination, peroxidase reactivation, and post-germination seedling growth were significantly stimulated.
Application of the known phenolics caffeic acid, feruic acid, or vanillin to the germination medium blocked seed germination
and suppressed peroxidase reactivation. The results described here indicate that WSPCs act as endogenous inhibitors in the
coat to control germination of Triticum aestivum seeds, and that inhibition of germination is at least partially caused by suppressing peroxidase reactivation. 相似文献
11.
A. Poljakoff-Mayber G. F. Somers E. Werker J. L. Gallagher 《American journal of botany》1992,79(3):249-256
Dormancy of Kosteletzkya virginica (L.) Presl. seeds is primarily due to the impermeability of the seed coat to water. The impermeable structure is assumed to be, in other Malvaceae, the palisade layer of the seed coat. The percentage of seeds capable of imbibition and germination increased with increasing time of storage at low temperatures, but the release from dormancy was not accompanied by decreased seed coat resistance to pressure. Under natural conditions, mechanical damage to the seed coat due to changes in temperature and/or abrasion may render the seeds water permeable. It is not clear what causes water permeability during storage under laboratory conditions. During seed maturation and drying, the inner epidermis of the tegmen partly separates from the rest of the seed coat and an air space, which makes the seed buoyant, is formed around the region of the chalazal cleft. The optimal temperature for germination of K. virginica seeds is between 28 and 30 C in light or darkness. 相似文献
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13.
In this study, we characterized a putative peroxidase Prx1 of Candida albicans by: 1) demonstrating the thioredoxin-linked peroxidase activity with purified proteins, 2) examining the sensitivity to several
oxidants and the accumulation of intracellular reactive oxygen species with a null mutant (prx1Δ), a mutant (C69S) with a point mutation at Cys69, and a revertant, and 3) subcelluar localization. Enzymatic assays showed
that Prx1 is a thioredoxin-linked peroxidase which reduces both hydrogen peroxide (H2O2) and tert-butyl hydroperoxide (t-BOOH). Compared with two other strong H2O2 scavenger mutants for TSA1 and CAT1, prx1Δ and C69S were less sensitive to H2O2, menadione and diamide at all concentrations tested, but were more sensitive to low concentration of t-BOOH. Intracellular reactive oxygen species accumulated in prx1Δ and C69S cells treated with t-BOOH but not H2O2. These results suggest that peroxidase activity of Prx1 is specified to t-BOOH in cells. In both biochemical and physiological cases, the evolutionarily conserved Cys69 was found to be essential
for the function. Immunocytochemical staining revealed Prx1 is localized in the cytosol of yeast cells, but is translocated
to the nucleus during the hyphal transition, though the significances of this observation are unclear. Our data suggest that
PRX1 has a thioredoxin peroxidase activity reducing both t-BOOH and H2O2, but its cellular function is specified to t-BOOH. 相似文献
14.
The Arabidopsis thaliana seed coat typically has a brown color due to the accumulation of flavonoid pigments in the testa. Mutants of A. thaliana with defects in pigment biosynthesis often produce seeds that are olive brown or even yellow in appearence, and the responsible
genetic loci are referred to as TRANSPARENT TESTA (TT). Large-scale screening for mutants affected in seed development and complementation analysis of a candidate mutant line
with all published A. thalianatt mutants identified a new tt locus designated tt15. The tt15 mutation maps to the lower part of chromosome 1. Mutant plants produced pale greenish-brown seeds whose dormancy was slightly
reduced. The phenotype was consistent with the maternal origin of the testa. Analysis of pigment accumulation and the study
of expression patterns of genes involved in flavonoid biosynthesis in tt15 plants and seeds indicated a seed-specific phenotype. Most notable was a reduction of the cyanidin and quercetin content
of tt15 seeds.
Received: 2 October 1998 / Accepted: 10 October 1998 相似文献
15.
Vandana Yadav Isabel Molina Kosala Ranathunge Indira Queralta Castillo Steven J. Rothstein Jason W. Reed 《The Plant cell》2014,26(9):3569-3588
Effective regulation of water balance in plants requires localized extracellular barriers that control water and solute movement. We describe a clade of five Arabidopsis thaliana ABCG half-transporters that are required for synthesis of an effective suberin barrier in roots and seed coats (ABCG2, ABCG6, and ABCG20) and for synthesis of an intact pollen wall (ABCG1 and ABCG16). Seed coats of abcg2 abcg6 abcg20 triple mutant plants had increased permeability to tetrazolium red and decreased suberin content. The root system of triple mutant plants was more permeable to water and salts in a zone complementary to that affected by the Casparian strip. Suberin of mutant roots and seed coats had distorted lamellar structure and reduced proportions of aliphatic components. Root wax from the mutant was deficient in alkylhydroxycinnamate esters. These mutant plants also had few lateral roots and precocious secondary growth in primary roots. abcg1 abcg16 double mutants defective in the other two members of the clade had pollen with defects in the nexine layer of the tapetum-derived exine pollen wall and in the pollen-derived intine layer. Mutant pollen collapsed at the time of anther desiccation. These mutants reveal transport requirements for barrier synthesis as well as physiological and developmental consequences of barrier deficiency. 相似文献
16.
Mutational and kinetic analysis of basic amino acid transport in the cyanobacterium Synechocystis sp. PCC 6803 总被引:4,自引:0,他引:4
Two nitrogen-deregulated mutants of Phanerochaete chrysosporium, der8-2 and der8-5, were isolated by subjecting wild type conidia to gamma irradiation, plating on Poly-R medium containing high levels of nitrogen, and identifying colonies that are able to decolorize Poly-R. The mutants showed high levels of ligninolytic activity (14C-synthetic lignin 14CO2), and lignin peroxidase, manganese peroxidase and glucose oxidase activities in both low nitrogen (2.4 mM) and high nitrogen (24 mM) media. The wild type on the otherhand displayed these activities in low nitrogen medium but showed little or no activities in high nitrogen medium. Fast protein liquid chromatographic analyses showed that the wild type as well as the der mutants produce three major lignin peroxidase peaks (designated L1, L2 and L3) with lignin peroxidase activity in low nitrogen medium. Furthermore, in low nitrogen medium, mutant der8-5 produced up to fourfold greater lignin peroxidase activity than that produced by the wild type. In high nitrogen medium, the wild type produced no detectable lignin peroxidase peaks whereas the mutants produced peaks L1 and L2, but not L3, and a new lignin peroxidase protein peak designated LN. Mutants der8-2 and der8-5 also produced high levels of glucose oxidase, an enzyme known to be associated with secondary metabolism and an important source of H2O2 in ligninolytic cultures, both in low and high nitrogen media. In contrast, the wild type produced high levels of glucose oxidase in low nitrogen medium and only trace amounts of this enzyme in high nitrogen medium. The results of this study indicate that the der mutants are nitrogen-deregulated for the production of a set of secondary metabolic activities associated with lignin degradation such as lignin peroxidases, manganese peroxidases and glucose oxidase. 相似文献
17.
Ines Capeleti Edicleia Aparecida Bonini Maria de Lourdes Lucio Ferrarese Aline Cristina Neres Teixeira Francisco Carlos Krzyzanowski Osvaldo Ferrarese-Filho 《Acta Physiologiae Plantarum》2005,27(1):103-108
Mechanical damage is one of the causes of great loss in the quality of soybean seeds during harvest and processing. Considerable
interest exists in the lignin since its deposition in the seed coat tissue provides mechanical resistance and protects the
cell against microorganisms. In addition, peroxidases might be involved in the oxidation of cinnamyl alcohols prior to their
polymerization during lignin formation. Thus, the aim of the present work was to analyze the lignin contents and peroxidases
activities of six Brazilian soybean cultivars (Savana, Paranagoiana, FT-10, Santa Rosa, Doko and Paraná) and their relationships
with the mechanical damage. Results showed that the lignin content and peroxidase activity in the seed coat significantly
differed among the soybean cultivars. Cultivars Doko and Paraná had the highest contents of lignin and peroxidases activities
while the other cultivars had lowest lignin contents and enzyme activities. Lignin content and peroxidase activity may be
reasonable indicators of resistance to mechanical damage in soybean seeds. 相似文献
18.
Peter Graven Chris G. de Koster Jaap J. Boon Ferry Bouman 《Plant Systematics and Evolution》1997,205(3-4):223-240
Cannaceae seeds have been analysed regarding seed coat structure, germination and macromolecular composition of the seed coats. Data of several mass spectrometric techniques were combined with those of microscopic and histochemical techniques to acquire insight into the functions of the seed coat.Cannaceae seeds have an exotestal layer of Malpighian cells with a hydrophobic and a hydrophilic part. The hydrophobic part is mainly responsible for the impermeability of the seed and contains silica, callose, lignin as water repellent substances. Water can only enter the seed after a certain temperature-induced opening of an imbibition lid. During imbibition the hydrophilic part of the Malpighian cells swells and the seed coat ruptures due to differences in pressure in the upper and lower part of the Malpighian cells. 相似文献
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20.
掌叶木(Handeliodendron bodinieri)是残遗于中国的稀有单种属植物,因人为破坏、生境特殊及自身特性的影响,资源稀少,被列为国家一级重点保护野生珍稀濒危植物。该研究以掌叶木种子为材料,研究了4种不同发芽条件下(带种皮、浓硫酸处理种皮、完全去除种皮、仅露出胚根)种子萌发性、种皮透水性、掌叶木果皮、假种皮、种皮和种仁四个部位不同浓度甲醇浸提物(0、3.125、6.25、12.5、25 mg/m L)对白菜种子萌发及幼苗生长的影响以及掌叶木各部位浸提物对种子萌发的影响。结果表明:(1)掌叶木种皮具有一定的透水性,为掌叶木种子的萌发提供必要的透水透气条件,不影响种子萌发前的水分吸收,但掌叶木种皮的机械阻碍、易霉变对种子的萌发影响较大。(2)掌叶木的果皮、假种皮、种皮和种仁甲醇浸提物对白菜种子的萌发和生长都有影响,尤其对白菜幼根的生长有较强的抑制作用,抑制强度依次是种仁果皮假种皮种皮,且随着浓度的升高,抑制作用增强。该研究结果揭示了掌叶木种子难发芽、发芽率低的原因,为掌叶木的人工扩繁和保护与利用奠定了基础。 相似文献