A Seed Shape Mutant of Arabidopsis That Is Affected in Integument Development.

Léon‐Kloosterziel, Karen M.; Keijzer, Christian J.; Koornneef, M.

doi:10.1105/tpc.6.3.385

Cited by 175 publications

(86 citation statements)

References 17 publications

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“…ap2 mutant seeds are altered in overall shape and in the shape of the epidermal cells (Bowman and Koornneef, 1994;Jofuku et al, 1994). We used electron and light microscopy to investigate more thoroughly the seed defects associated with the strong ap2-6 mutant allele.…”

Section: Mutants Affecting Differentiation Of Seed Coat Epidermal Andmentioning

confidence: 99%

“…Observation of ap2 seeds showed altered seed shape and the absence of mucilage and columellae (Bowman and Koornneef, 1994;Jofuku et al, 1994). Mutants defective in ABERRANT TESTA SHAPE, a gene involved in ovule integument development, have heart-shaped seeds that have a reduced amount of mucilage (Léon-Kloosterziel et al, 1994). Finally, abscisic acid deficient1 mutants, as part of their syndrome resulting from lack of abscisic acid, produce a reduced amount of mucilage (Karssen et al, 1983).…”

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Isolation and Characterization of Mutants Defective in Seed Coat Mucilage Secretory Cell Development in Arabidopsis

Western¹

2001

Plant Physiology

221

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In Arabidopsis, fertilization induces the epidermal cells of the outer ovule integument to differentiate into a specialized seed coat cell type producing extracellular pectinaceous mucilage and a volcano-shaped secondary cell wall. Differentiation involves a regulated series of cytological events including growth, cytoplasmic rearrangement, mucilage synthesis, and secondary cell wall production. We have tested the potential of Arabidopsis seed coat epidermal cells as a model system for the genetic analysis of these processes. A screen for mutants defective in seed mucilage identified five novel genes (MUCILAGE-MODIFIED [MUM]1-5). The seed coat development of these mutants, and that of three previously identified ones (TRANSPARENT TESTA GLABRA1, GLABRA2, and APETALA2) were characterized. Our results show that the genes identified define several events in seed coat differentiation. Although APETALA2 is needed for differentiation of both outer layers of the seed coat, TRANSPARENT TESTA GLABRA1, GLABRA2, and MUM4 are required for complete mucilage synthesis and cytoplasmic rearrangement. MUM3 and MUM5 may be involved in the regulation of mucilage composition, whereas MUM1 and MUM2 appear to play novel roles in post-synthesis cell wall modifications necessary for mucilage extrusion.Fertilization of the angiosperm ovule not only results in the development of the embryo and endosperm, but also initiates differentiation of the ovule integuments to form the seed coat. The seed coat consists of multiple specialized cell layers that play important roles in embryo protection and the regulation of germination. One specialization is known as myxospermy, a property of epidermal cells whereby they produce large quantities of pectic polysaccharide (mucilage; Frey-Wyssling, 1976; Grubert, 1981; Boesewinkel and Bouman, 1995). Myxospermy is commonly found in species of the Brassicaceae, Solanaceae, Linaceae, and Plantaginaceae, where mucilage forms a gel-like capsule surrounding the seed upon imbibition. Proposed roles for mucilage include facilitating seed hydration and/or dispersal. Mucilages are also found in the root cap and transmitting tract (Frey-Wyssling, 1976; Esau, 1977), where they foster root tip and pollen tube growth, respectively.Mucilages are largely composed of pectins, a heterogeneous group of complex, acidic polysaccharides that also comprise the majority of the plant cell wall matrix. Dicotyledonous pectins largely consist of poly-GalUA (PGA) and rhamnogalacturonan I (RG I; Brett and Waldron, 1990; Carpita and Gibeaut, 1993; Cosgrove, 1997). PGA is composed of an unbranched chain of ␣1,4-linked GalUA residues, whereas RG I is a highly branched polysaccharide with a backbone of alternating ␣1,4-linked GalUA and ␣1,2-linked rhamnose (Rha), with sugar side chains attached to the Rha residues (Brett and Waldron, 1990). The degree of gelling of pectins is largely dependent on ionic bonding between PGA molecules and free divalent calcium. Thus, cell wall fluidity is affected by the degree of methyl esterification of...

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Section: Mutants Affecting Differentiation Of Seed Coat Epidermal Andmentioning

confidence: 99%

mentioning

confidence: 99%

Isolation and Characterization of Mutants Defective in Seed Coat Mucilage Secretory Cell Development in Arabidopsis

Western¹

2001

Plant Physiology

221

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“…One group of these mutants is affected in the testa structure or testa color. It is hypothesized that these mutations allow an easier penetration of the radicle through the testa because this structure is a mechanical barrier (Léon-Kloosterziel et al, 1994). In addition, a number of mutants have been described in which reduced dormancy is due to the embryo genotype.…”

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Arabidopsis Mutants with a Reduced Seed Dormancy

Léon‐Kloosterziel¹,

Bunt²,

Zeevaart³

et al. 1996

Plant Physiol.

Self Cite

133

105

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The development of seed dormancy is an aspect of seed maturation, the last stage of seed development. To isolate mutants of Arabidopsis thaliana that are affected in this process, we selected directly for the absence of dormancy among freshly harvested M, seeds. l h e screen yielded two mutants exhibiting a reduced dormancy, rdol and rdo2, that are specifically affected in dormancy determined by the embryo. l h e rdol and rd02 mutants show normal levels of abscisic acid and the same sensitivity to abscisic acid, ethylene, auxin, and cytokinin as the wild type. l h e rdolmutant but not the rdol mutant has a reduced sensitivity to the gibberellin biosynthesis inhibitor tetcyclacis. Double-mutant analysis suggested that the R D O l and R D 0 2 genes are involved in separate pathways leading to the development of dormancy. We assume that the R D 0 2 gene controls a step in the induction of dormancy that is most likely induced by abscisic acid and is expressed as an increase of the gibberellin requirement for germination. ~Many plant species produce seeds that are dormant when they are released from the plant. Seed dormancy has been defined as a temporary failure of a viable seed to germinate in conditions that favor germination when the restrictive state (i.e. dormancy) has come to an end (Simpson, 1990). Dormancy is relieved by a cold treatment of seeds allowed to imbibe and during dry storage of the seeds, often referred to as after-ripening. It can be reinduced (secondary dormancy) when the conditions do not meet a11 requirements for germination (Karssen, 1982). The cycling of dormancy, leading to seedling emergence in specific periods of the year, is thought to reflect the seeds' responsiveness to the environmental factors temperature, light, and nitrate (Hilhorst et al., 1995).The small crucifer Avabidopsis thaliana exhibits seed dormancy, allowing the seeds in the natural situation to survive the dry summer period and germinate in autumn (Baskin and Baskin, 1972). The many environmental and genetic factors that determine seed dormancy in Arabidopsis have been reviewed by Koornneef and Karssen (1994). Dormancy differences between seed lots can be "measured" by comparing the germination percentage of these seed lots after a specified period of dry storage. The conditions during seed development and the duration and conditions of dry storage after harvest influence the degree of dormancy, which is expressed in the germination behavior of the seeds. Therefore, these parameters and the test conditions have to be identical when genotypes are compared. Despite these precautions, seeds from different plants of a homozygous genotype may show larger differences than statistically expected.The nature and variability of seed dormancy determine that this trait behaves genetically more as a quantitative trait than as a qualitative trait. However, severa1 Arabidopsis mutants have been described that have a reduced dormancy. One group of these mutants is affected in the testa structure or testa color. It is hypothesized that ...

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“…Les plus importants sont la nutrition de l'embryon [15] et la taille de la graine [16,17]. En outre, des mutants de forme ou de couleur des téguments (mutants transparent testa, tt) (figure 2 D) montrent une dormance et une viabilité réduite ainsi qu'une perméabilité aux solutés augmentée [18].…”

Section: Mutant De Tégumentsunclassified

NORD : IMPACTS DES BIOTECHNOLOGIES RECHERCHES Approches moléculaires de la qualité et du développement des graines

Dubreucq¹,

Grappin²,

Miquel³

et al. 2001

OCL

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Résumé :Les semences constituent le maillon essentiel de la production végétale car elles sont à la fois le vecteur de la multiplication des plantes et la source de denrées alimentaires. L'agriculture moderne exige le respect des critères de qualité des semences qui ne sont évidemment pas les mêmes suivant que l'utilisation des semences sera alimentaire, industrielle ou de simple semis. Du point de vue alimentaire ou industriel, la qualité se définit en fonction de la nature et du rendement de l'extraction du produit d'intérêt. Lorsque la graine est utilisée comme semence, la qualité est appréciée suivant des critères qui sont la conformité génétique, l'état sanitaire et la capacité germinative. Les normes qualitatives alors retenues concourent à l'obtention de peuplements homogènes et vigoureux. La semence idéale doit évidemment combiner ces différents critères de qualité. Les bases biologiques qui sous-tendent la plupart des critères de qualité sont encore très mal connues et leur élucidation demeure un défi scientifique majeur. Summary : Seeds are essential for plant propagation and crop production and must satisfy the increasingly diverse requirements of both modern agriculture and the agro-industry. The biological bases of seed quality are still poorly understood. Progress in this area will no doubt emerge from the identification of genes that control quality parameters, through the tremendous advances made using genomic based techniques. In this way, the use of 50,000 Arabidopsis thaliana T-DNA mutant lines, developed in France, at the Inra Versailles has enabled us to isolate genes whose functions are essential for seed development and maturation, e.g. storage compound synthesis and deposition, and tegument composition. Mutants have been isolated that are either strongly impaired in protein glycosylation (glycosidase I mutant) or whose lipid composition is modified (diacylglycerol acyltransferase: DGAT mutant). The corresponding cloned genes should prove useful in biotechnological applications for the reduction of the allergenicity of engineered proteins produced in plants and for modifying seed lipid composition respectively. New Transparent Testa genes have also been obtained that play a role in the control of pigment deposition in the seed testa. Engineering the composition of seed coats is a real challenge for the improvement of the nutritional value of seeds for animal feeding. The zeaxanthin epoxidase gene has been cloned, as this is required for the biosynthesis of the hormone abscisic acid (ABA). Using this gene it has been possible to Article disponible sur le site http://www.ocl-journal.org ou http://dx

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A Seed Shape Mutant of Arabidopsis That Is Affected in Integument Development.

Cited by 175 publications

References 17 publications

Isolation and Characterization of Mutants Defective in Seed Coat Mucilage Secretory Cell Development in Arabidopsis

Isolation and Characterization of Mutants Defective in Seed Coat Mucilage Secretory Cell Development in Arabidopsis

Arabidopsis Mutants with a Reduced Seed Dormancy

NORD : IMPACTS DES BIOTECHNOLOGIES RECHERCHES Approches moléculaires de la qualité et du développement des graines

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