Development of endosperm inScrophularia himalensis with a discussion on the variation in the endosperm of the tribeScrophularieae (Scrophulariaceae)

Scrophularia himalensis has anab initio cellular endosperm. A transverse division separates a micropylar chamber from a chalazal chamber. The second division is vertical in both, the third is also vertical but at right angles to the second and restricted to the micropylar chamber just as the fourth transverse division. The four-celled micropylar haustorium is branched, highly aggressive, and persists for a long time during seed development. The bicelled chalazal haustorium is non-aggressive and is relatively short-lived. The endosperm proper is ruminate. Variation in the early ontogeny of the endosperm and the structure of endosperm haustoria in the tribeScrophularieae are evaluated.     

Oxidative protein folding: Selective pressure for prolamin evolution in rice

During seed development, endosperm cells of highly productive cereals, including rice, synthesize disulfide-rich proteins in large amounts and deposit them into storage organelles. Disulfide bond formation involves electron transfer and generates H₂O₂ as a by-product. To ensure proper development and maturation of seeds, the endosperm cells must supply large amounts of oxidizing equivalents to dithiols in nascent proteins in a controlled manner. This review compares multiple oxidative protein folding systems in yeast, cultured human cells, and rice endosperm. We discuss possible roles of ERO1, other sulfhydryl oxidases, and the protein disulfide isomerase family in the formation of disulfide bonds in storage proteins and the development of protein bodies. Rice prolamins, encoded by a multigene family, are divided into Cys-rich and Cys-depleted subgroups. We discuss the potential importance of disulfide bond formation in the evolution of the prolamin family in japonica rice.     

ENDOSPERM DEFECTIVE1 Is a Novel Microtubule-Associated Protein Essential for Seed Development in Arabidopsis

Early endosperm development involves a series of rapid nuclear divisions in the absence of cytokinesis; thus, many endosperm mutants reveal genes whose functions are essential for mitosis. This work finds that the endosperm of Arabidopsis thaliana endosperm-defective1 (ede1) mutants never cellularizes, contains a reduced number of enlarged polyploid nuclei, and features an aberrant microtubule cytoskeleton, where the specialized radial microtubule systems and cytokinetic phragmoplasts are absent. Early embryo development is substantially normal, although occasional cytokinesis defects are observed. The EDE1 gene was cloned using a map-based approach and represents the pioneer member of a conserved plant-specific family of genes of previously unknown function. EDE1 is expressed in the endosperm and embryo of developing seeds, and its expression is tightly regulated during cell cycle progression. EDE1 protein accumulates in nuclear caps in premitotic cells, colocalizes along microtubules of the spindle and phragmoplast, and binds microtubules in vitro. We conclude that EDE1 is a novel plant-specific microtubule-associated protein essential for microtubule function during the mitotic and cytokinetic stages that generate the Arabidopsis endosperm and embryo.     

The specialized chalazal endosperm inArabidopsis thaliana andLepidium virginicum (Brassicaceae)

Summary Endosperm of the nuclear type initially develops into a large multinucleate syncytium that lines the central cell. This seemingly simple wall-less cytoplasm can, however, be highly differentiated. In developing seeds of members of the family Brassicaceae the curved postfertilization embryo sac comprises three chambers or developmental domains. The syncytium fills the micropylar chamber around the embryo, spreads as a thin peripheral layer surrounding a large central vacuole in the central chamber, and is organized into individual nodules and a large multinucleate cyst in the chalazal tip. Later in development, after the endosperm has cellularized in the micropylar and central chambers, the chalazal endosperm cyst remains syncytial and shows considerable internal differentiation. The chalazal endosperm cyst consists of a domelike apical region that is separated from the cellularized endosperm by a remnant of the central vacuole and a basal haustorial portion which penetrates the chalazal proliferative tissue atop the vascular supply. In the shallow chalazal depression ofArabidopsis thaliana, the cyst is mushroom-shaped with short tentacle-like processes penetrating the maternal tissues. The long narrow chalazal channel ofLepidium irginicum is filled by an elongate stalklike portion of the cyst. In both, the dome contains a labyrinth of endoplasmic reticulum, dictyosomes with associated vesicles, nuclei, and plastids. The basal portions, which lack the larger organelles, exhibit extensive wall ingrowths and contain parallel arrays of microtubules. The highly specialized ultrastructure of the chalazal endosperm cyst and its intimate association with degrading chalazal proliferative cells suggest an important role in loading of maternal resources into the developing seed.     

大车前胚乳发育的超微结构研究

采用透射电镜技术对大车前(Plantago major L.)胚乳发育的超微结构进行了研究。结果表明:(1)大车前为细胞型胚乳;初生胚乳核经一次横分裂产生1个珠孔室细胞和1个合点室细胞;珠孔室两次纵向分裂一次横向分裂形成2层8个细胞,位于上层的4个细胞发育为4个珠孔吸器,位于下层的4个细胞发育为胚乳本体;合点室细胞进行一次核分裂,发育为两核的合点吸器。(2)珠孔吸器呈管状插入珠被组织,珠孔端细胞壁加厚呈现少量分支并具有壁内突,壁内突周围细胞质里分布着大量线粒体、粗面内质网、高尔基体、质体等,细胞核与核仁明显,细胞质浓厚,代谢活动旺盛;球胚期,珠孔吸器的体积呈现最大值,珠孔吸器周围的珠被组织均被水解,形成明显的空腔。珠孔吸器从珠被组织吸收并转运营养物质至胚乳本体,参与胚乳的构建与营养物质的贮藏。球胚后期,珠孔吸器逐渐退化。(3)4个胚乳本体原始细胞具旺盛的分生能力,经不断的平周与垂周分裂增加胚乳细胞数目,使胚乳本体呈现圆球体状,并将胚包围其中;珠孔吸器、合点吸器以及珠被绒毡层吸收转运的营养物质贮存在胚乳本体;球胚后期,随着胚柄的退化,胚体周围的胚乳细胞被水解,为发育的胚所利用。(4)合点吸器的2个细胞核与核仁巨大,线粒体、质体、高尔基体、内质网主要绕核分布,液泡化明显;胚体与胚乳本体的体积增大,逐渐将合点吸器向胚珠合点部位挤压,合点吸器周围的合点组织逐渐被水解,形成巨大空腔。合点吸器自珠心组织吸收并转运营养物质至胚乳本体,参与胚乳的结构构建与营养物质的贮藏。球胚后期,合点吸器逐渐失去功能,呈现退化状态。     

Molecular cloning, characterization and expression of cDNA encoding translationally controlled tumor protein (TCTP) from Jatropha curcas L

A cDNA encoding translationally controlled tumor protein (TCTP) of Jatropha curcas L., JcTCTP, was isolated from an endosperm cDNA library. JcTCTP consisted of a 5?? untranslated region (UTR) of 526 bp, a 3?? UTR of 377 bp and an open reading frame (ORF) of 507 bp, encoding a protein of 168 amino acid residues, which contained two signature sequences of TCTP family. Its deduced amino acid sequence was similar to the other known plants TCTPs in a range of 77.4?C92.3%. Expression of JcTCTP was the highest in the stem, endosperm at embryo formation stage and embryo of J. curcas tissues, and the lowest in the endosperm at seminal leaf embryo stage and flower, demonstrating a pattern of temporal and spatial specific expression.     

Seed development in Malpighiaceae species with an emphasis on the relationships between nutritive tissues

Malpighiaceae ovules have a well-developed nucellus; previous observations indicate that during seed development, the endosperm does not proliferate, thus, remaining scarce. This study aimed at identifying the nutritive tissues during seed development in Malpighiaceae, focusing especially on the endosperm. We analysed the seed development of Janusia mediterranea, J. occhionii, Mascagnia cordifolia, and Tetrapterys chamaecerasifolia, which were collected and processed by traditional methods for light microscopy. Ovules are subcampylotropous, crassinucellate and unitegmic in Janusia and bitegmic in M. cordifolia and T. chamaecerasifolia. The nucellus is well developed and protrudes through the micropyle, touching the funicular obturator. During development, a pachychalaza is formed, and the integuments coalesce in bitegmic species. Through a series of nucellar cell divisions, the perisperm is formed. In Janusia species, the endosperm is not produced. In M. cordifolia and T. chamaecerasifolia, the endosperm is nuclear, but it is scarce and ephemeral. The mature seed is exalbuminous, and the perisperm is consumed, and thus, the mature embryo is total. The absence of endosperm in Janusia is newly observed for the family and indicates functional transfer for the abundant perisperm.     

THE DEVELOPMENT OF THE SEED IN ANDROGRAPHIS SERPYLLIFOLIA

Mohan Ram , H. Y. (U. Delhi, India.) The development of the seed in Andrographis serpyllifolia. Amer. Jour. Bot. 47(3) : 215—219. Illus. 1960.–Andrographis serpyllifolia, a member of the Acanthaceae, has an embryo sac with a bifurcated chalazal part. At the time of fertilization both synergids and antipodal cells disintegrate. Early in its development the endosperm is composed of 3 distinct parts: (1) a binucleate densely cytoplasmic chalazal haustorium; (2) a large binucleate micropylar haustorium; and (3) a central chamber which develops into the endosperm proper. The divisions in the central endosperm chamber are ab initio cellular. A few of the endosperm cells elongate enormously, ramify into the integument and destroy the surrounding cells. These cells have been termed secondary haustoria. Due to the unequal destruction of the integument, the endosperm assumes a ruminate condition. The mature seed is nearly naked because the seed coat is almost completely digested. The embryo has a long suspensor. The micropylar cells of the suspensor are hypertrophied and multinucleate. Contrary to Mauritzon's (1934) belief, the course of endosperm development is markedly different from that observed in Thunbergia. So far, albuminous seeds have been reported only in the subfamily Nelsonioideae. The present investigation provides a case of its occurrence in the Acanthoideae also.     

Degree of pectin methyl esterification in endosperm cell walls is involved in embryo bending in Arabidopsis thaliana

The endosperm is a transitory structure involved in proper embryo elongation. The cell walls of mature seed endosperm are generally composed of a uniform distribution of cellulose, unesterified homogalacturonans, and arabinans. Recent studies suggest that changes in cell wall properties during endosperm development could be related to embryo growth. The degree of methyl esterification of homogalacturonans may be involved in this endosperm tissue remodelling. The relevance of the degree of homogalacturonan methyl esterification during seed development was determined by immunohistochemical analyses using a panel of probes with specificity for homogalaturonans with different degrees of methyl esterification. Low-esterified and un-esterified homogalacturonans were abundant in endosperm cells during embryo bending and were also detected in mature embryos. BIDXII (BDX) could be involved in seed development, because bdx-1 mutants had misshapen embryos. The methyl esterification pattern described for WT seeds was different during bdx-1 seed development; un-esterified homogalacturonans were scarcely present in the cell walls of endosperm in bending embryos and mature seeds. Our results suggested that the degree of methyl esterification of homogalacturonans in the endosperm cell wall may be involved in proper embryo development.