Trehalose 6-phosphate Controls Seed Filling by Inducing Auxin Biosynthesis

Plants undergo several developmental transitions during their life cycle. One of these, the differentiation of the young embryo from a meristem-like structure into a highly-specialized storage organ, is vital to the formation of a viable seed. For crops in which the seed itself is the end product, effective accumulation of storage compounds is of economic relevance, defining the quantity and nutritive value of the harvest yield. However, the regulatory networks underpinning the phase transition into seed filling are poorly understood. Here we show that trehalose 6-phosphate (T6P), which functions as a signal for sucrose availability in plants, mediates seed filling processes in seeds of the garden pea (Pisum sativum), a key grain legume. Seeds deficient in T6P are compromised in size and starch production, resembling the wrinkled seeds studied by Gregor Mendel. We show also that T6P exerts these effects by stimulating the biosynthesis of the pivotal plant hormone, auxin. We found that T6P promotes the expression of the auxin biosynthesis gene TRYPTOPHAN AMINOTRANSFERASE RELATED2 (TAR2), and the resulting effect on auxin levels is required to mediate the T6P-induced activation of storage processes. Our results suggest that auxin acts downstream of T6P to facilitate seed filling, thereby providing a salient example of how a metabolic signal governs the hormonal control of an integral phase transition in a crop plant.

Transformasi Genetik Kedelai dengan Gen Proteinase Inhibitor II Menggunakan Teknik Penembakan Partikel

<p class="p1">An experiment was conducted at the Molecular Biology and Genetic Engineering Laboratory of BB-Biogen, Bogor with an objective to obtain transgenic soybean plants containing the <em>proteinase inhibitor </em>II (<em>pin</em>II) gene. The experiment consisted of three steps, i.e., optimalization of the soybean transformation technique using the <em>gus </em>gene; transformation of soybean using the <em>pin</em>II gene, and molecular analysis of the transformed soybean plants. Two type of explants (young embryo and cotyledon) were bombarded with <em>p</em>RQ6 plasmid containing the <em>gus </em>gene with the following treatment: Helium gas pressure (1100 psi and 1300 psi), shoot distance (5 and 7 cm), and number of bombardment (1x and 2x). The result of <em>gus </em>assay indicated that the best bombardment was done on young cotyledon explants with 1100 psi Helium pressure, shoot distance 5 cm, and 1x bombardment. Transformation of the soybean explant using the <em>pin</em>II gene (inside the <em>p</em>TWa plasmid) was conducted using the best bombardment treatment from the first activity. Two plants from c.v. Wilis (WP<span class="s1">1</span>, WP<span class="s1">2</span>) and three plants from c.v. Tidar (TP<span class="s1">1</span>, TP<span class="s1">2</span>, TP<span class="s1">3</span>) were recovered from regeneration and selection of the transformed explants. Molecular analysis of the regenerated plants using the PCR technique showed that only WP<span class="s1">2 </span>contained the <em>pin</em>II gene. This plant was fertile and will be used for further evaluation.</p>

Rape embryogenesis I. The proembryo development

The development of the proembryo of rape <i>Brassica napus</i> L. from the zygote to the young embryo proper is described. A number of regularities were found in the direction, succession, and distribution of segmental and differentiating divisions of the proembryo. The direction of the divisions seems to foe determined by the direction of growth and the shape of the cells. The termyoung embryo proper is proposed to denote the globular embryo which already possesses separate plerome and periblem mother-cells and mother-cells of the iec layer and of clumella. The body of the embryo proper is derived from the apical cell ca which arose from the first division of the zygote and from the hypophysis - the only suspensor cell which closes the spheroid of the embryo. The development of the <i>Brassica napus</i> L. proembryo follows the sub-archetype <i>Capsella bursa-pastoris</i> in the IV megarchetype of Soueges.

Nonhomologous Chromosome Pairing in Aegilops-Secale Hybrids

Intergeneric hybrids and amphidiploid hybrids from crosses of Aegilopstauschii and Secale cereale were produced using young embryo rescue. The hybrids showed complete sets of both parental chromosomes. The dihaploid plants showed an average meiotic pairing configuration of 10.84 I + 1.57 II + 0.01 III. Genomic in situ staining revealed 3 types of bivalent associations, i.e. D-D, R-R and D-R at frequencies of 8.6, 8.2 and 83.3%, respectively. Trivalents consisted of D-R-D or R-D-R associations. These results suggested that both intra- and intergenomic chromosome homology were contributed to chromosome pairing. Derived amphidiploids with 2n = 28 paired at metaphase I of meiosis as 4.51 I + 11.70 II + 0.03 III. Chromosome pairing of amphidiploids appeared more or less regular, i.e. bivalent-like with some trivalent configurations.

Epigenetic control of cell invasion – the trophoblast model

Trophoblast implantation and placentation allow the survival of the young embryo and its normal development inside the uterus. In order for these processes to function properly, the trophoblast has to undergo a series of characteristic changes that lead to its adhesion and invasion of the uterus. This is achieved, among other mechanisms, by inactivation of specific tumor suppressor genes, commonly by methylation of their promoters. Cell adhesion and tissue invasion are also characteristics of malignant tumors and patterns of methylation similar to that seen in trophoblast are found in various tumor types. Another important mechanism that aids trophoblast cells invasion is their transition from epithelial to mesenchymal phenotype. Such a transition is also a common characteristic of invading malignant cells. Thus, studying tissue invasion and its control mechanisms can benefit the understanding of both the trophoblast and malignant cells behavior.

Invited Review: Effect of oxygen deprivation on cell cycle activity: a profile of delay and arrest

One of the most fascinating fields that have emanated in the past few decades is developmental biology. This is not only the case from a research point of view but also from the angle of clinical care and treatment strategies. It is now well demonstrated that there are many diseases (some believe all diseases) that have their roots in embryogenesis or in early life, where nature and environment often team up to facilitate the genesis of disease. There is probably no better example to illustrate the interactions between nature and environment than in early life, as early as in the first several cell cycles. As will be apparent in this review, the cell cycle is a very regulated activity and this regulation is genetic in nature, with checkpoint proteins playing an important role in controlling the timing, the size, and the growth of daughter cells. However, it is also very clear, as will be discussed in this work, that the microenvironment of the first dividing cells is so important for the outcome of the organism. In this review, we will focus on the effect of one stress, that of hypoxia, on the young embryo and its cell division and growth. We will first review some of the cell cycle definitions and stages and then review briefly our current knowledge and its gaps in this area.

Pyrophosphate-dependent fructose-6-phosphate 1-phosphotransferase overexpression in transgenic tobacco: physiological and biochemical analysis of source and sink tissues

Transgenic Nicotiana tabacum L. (tobacco) plants expressing an unregulated gene for pyrophosphate-dependent fructose-6-phosphate 1-phosphotransferase (PFP) from the fermentor protist Giardia lamblia were produced. Independently transformed lines revealed a high level of Giardia PFP activity but unaltered activities of native plant PFP, phosphofructokinase, and fructose-1,6-bisphosphatase. Transgenic plants exhibited a decrease in total biomass but no dramatic physiological or morphological alterations or significant reduction of seed yield. Both source and sink tissues demonstrated altered partitioning: leaf starch was significantly lower at the beginning and end of the daily light period and young seeds had lower starch but higher lipid levels, and these changes were correlated with PFP activity. Transgenic seeds had significantly higher percentages of germination, and microscopic examination of these seeds showed a temporal enhancement in growth of the young embryo. The significance of these results as they relate to our current understanding of PFP is discussed.Key words: pyrophosphate-dependent fructose-6-phosphate 1-phosphotransferase (PFP), transgenic, Nicotiana tabacum, glycolysis, photosynthate partitioning.

A subtilisin-like serine protease is required for epidermal surface formation inArabidopsisembryos and juvenile plants

The surfaces of land plants are covered with a cuticle that is essential for retention of water. Epidermal surfaces of Arabidopsis thaliana embryos and juvenile plants that were homozygous for abnormal leaf shape1 (ale1) mutations were defective, resulting in excessive water loss and organ fusion in young plants. In ale1 embryos, the cuticle was rudimentary and remnants of the endosperm remained attached to developing embryos. Juvenile plants had a similar abnormal cuticle. The ALE1 gene was isolated using a transposon-tagged allele ale1-1. The predicted ALE1 amino acid sequence was homologous to those of subtilisin-like serine proteases. The ALE1 gene was found to be expressed within certain endosperm cells adjacent to the embryo and within the young embryo. Expression was not detected after germination. Our results suggest that the putative protease ALE1 affects the formation of cuticle on embryos and juvenile plants and that an appropriate cuticle is required for separation of the endosperm from the embryo and for prevention of organ fusion.

The Short antennae gene of Tribolium is required for limb development and encodes the orthologue of the Drosophila Distal-less protein

Insects bear a stereotyped set of limbs, or ventral body appendages. In the highly derived dipteran Drosophila melanogaster, the homeodomain transcription factor encoded by the Distal-less (Dll) gene plays a major role in establishing distal limb structures. We have isolated the Dll orthologue (TcDll) from the beetle Tribolium castaneum, which, unlike Drosophila, develops well-formed limbs during embryogenesis. TcDll is initially expressed at the sites of limb primordia formation in the young embryo and subsequently in the distal region of developing legs, antennae and mouthparts except the mandibles. Mutations in the Short antennae (Sa) gene of Tribolium delete distal limb structures, closely resembling the Dll phenotype in Drosophila. TcDll expression is severely reduced or absent in strong Sa alleles. Genetic mapping and molecular analysis of Sa alleles also support the conclusion that TcDll corresponds to the Sa gene. Our data indicate functional conservation of the Dll gene in evolutionarily distant insect species. Implications for evolutionary changes in limb development are discussed.

Catalase isozymes as biochemical markers of different developmental stages in cypress (Cuptessussempervirens)

The expression of catalase isozymes has been investigated to define the different developmental stages of cypress (Cupressussempervirens L). To examine the temporal pattern of catalase expression during development, catalases in dry seeds, young embryos, and different tissues of the mature plant were characterized by native polyacrylamide gel electrophoresis. The data indicated the presence of two patterns of expression: one specific to the seed and young embryo and another for the mature plant. Defined isoforms were specific to each developmental time. The results indicated that different catalase isozymes are developmentally expressed. Consequently the changes in their expression pattern can be used to define the development stages of the tree.