Heart Stage Of Embryo Development Research Articles

Ultrastructural aspects of the embryo and different endosperm compartments, inEruca sativaHill cv. Nemat (Brassicaceae) during Heart and Torpedo stages

Abstract These observations are the first on the ultrastructure of the embryo and the endosperm of Eruca sativa Hill. We investigated the cv. Nemat, which is characterized by a particularly high amount of lipids and glucosinolates. Our observations suggested that the thick and abundant micropylar endosperm, completely surrounding the suspensor, may be the main active source of nutrients for the embryo. This endosperm, like the central chamber endosperm, is particularly rich in functional chloroplasts and cellularizes later with respect to the other previ- ously investigated Brassicaceae. The last (distal with respect to the embryo) suspensor cell exhibits important features related to the passage of nutrients, such as wall ingrowths. In fact these ingrowths appear as highly convoluted labyrinthine wall projections. Such ultrastructural features are typical of transfer cells. The accumu- lation stage in E. sativa cv. Nemat appears to occur early (Heart stage of embryo development, as Brassica na pus). The ...

RETARDED GROWTH OF EMBRYO1, a New Basic Helix-Loop-Helix Protein, Expresses in Endosperm to Control Embryo Growth

We have isolated two dominant mutants from screening approximately 50,000 RIKEN activation-tagging lines that have short inflorescence internodes. The activation T-DNAs were inserted near a putative basic helix-loop-helix (bHLH) gene and expression of this gene was increased in the mutant lines. Overexpression of this bHLH gene produced the original mutant phenotype, indicating it was responsible for the mutants. Specific expression was observed during seed development. The loss-of-function mutation of the RETARDED GROWTH OF EMBRYO1 (RGE1) gene caused small and shriveled seeds. The embryo of the loss-of-function mutant showed retarded growth after the heart stage although abnormal morphogenesis and pattern formation of the embryo and endosperm was not observed. We named this bHLH gene RGE1. RGE1 expression was determined in endosperm cells using the beta-glucuronidase reporter gene and reverse transcription-polymerase chain reaction. Microarray and real-time reverse transcription-polymerase chain reaction analysis showed specific down-regulation of putative GDSL motif lipase genes in the rge1-1 mutant, indicating possible involvement of these genes in seed morphology. These data suggest that RGE1 expression in the endosperm at the heart stage of embryo development plays an important role in controlling embryo growth.

MINISEED3 ( MINI3 ), a WRKY family gene, and HAIKU2 ( IKU2 ), a leucine-rich repeat ( LRR ) KINASE gene, are regulators of seed size in Arabidopsis

We have identified mutant alleles of two sporophytically acting genes, HAIKU2 (IKU2) and MINISEED3 (MINI3). Homozygotes of these alleles produce a small seed phenotype associated with reduced growth and early cellularization of the endosperm. This phenotype is similar to that described for another seed size gene, IKU1. MINI3 encodes WRKY10, a WRKY class transcription factor. MINI3 promoter::GUS fusions show the gene is expressed in pollen and in the developing endosperm from the two nuclei stage at approximately 12 hr postfertilization to endosperm cellularization at approximately 96 hr. MINI3 is also expressed in the globular embryo but not in the late heart stage of embryo development. The early endosperm expression of MINI3 is independent of its parent of origin. IKU2 encodes a leucine-rich repeat (LRR) KINASE (At3g19700). IKU2::GUS has a similar expression pattern to that of MINI3. The patterns of expression of the two genes and their similar phenotypes indicate they may operate in the same genetic pathway. Additionally, we found that both MINI3 and IKU2 showed decreased expression in the iku1-1 mutant. IKU2 expression was reduced in a mini3-1 background, whereas MINI3 expression was unaltered in the iku2-3 mutant. These data suggest the successive action of the three genes IKU1, IKU2, and MINI3 in the same pathway of seed development.

Isolation of GUS marker lines for genes expressed in Arabidopsis endosperm, embryo and maternal tissues.

In order to identify marker lines expressing GUS in various endosperm compartments and at different developmental stages, a collection of Arabidopsis thaliana (L.) Heynh. promoter trap lines were screened. The screen identified 16 lines displaying GUS-reporter gene expression in the endosperm, embryo and other seed organs. The distinctive patterns of GUS expression in these lines provide molecular markers for most cell compartments in the endosperm of Arabidopsis seeds at all developmental stages, and represent a valuable research tool for characterizing present and future Arabidopsis seed mutants. GUS expression patterns of these 16 lines are presented here. One line showed chalazal endosperm-specific GUS activity at the heart stage of embryo development. In six lines embryo-specific GUS activity was detected. Six lines exhibited GUS activity predominantly in the endosperm and embryo while two lines showed strong GUS activity in all seed organs. In one line GUS activity was detected in integuments and syncytial endosperm, while the GUS activity at the cotyledonary stage of the embryo was seed coat-specific. In addition, two funiculus markers and two silique markers expressed in the abscission zone and the guard cells are also presented.

Isolation of GUS marker lines for genes expressed in Arabidopsis endosperm, embryo and maternal tissues

In order to identify marker lines expressing GUS in various endosperm compartments and at different developmental stages, a collection of Arabidopsis thaliana (L.) Heynh. promoter trap lines were screened. The screen identified 16 lines displaying GUS‐reporter gene expression in the endosperm, embryo and other seed organs. The distinctive patterns of GUS expression in these lines provide molecular markers for most cell compartments in the endosperm of Arabidopsis seeds at all developmental stages, and represent a valuable research tool for characterizing present and future Arabidopsis seed mutants. GUS expression patterns of these 16 lines are presented here. One line showed chalazal endosperm‐specific GUS activity at the heart stage of embryo development. In six lines embryo‐specific GUS activity was detected. Six lines exhibited GUS activity predominantly in the endosperm and embryo while two lines showed strong GUS activity in all seed organs. In one line GUS activity was detected in integuments and syncytial endosperm, while the GUS activity at the cotyledonary stage of the embryo was seed coat‐specific. In addition, two funiculus markers and two silique markers expressed in the abscission zone and the guard cells are also presented.

Gene transfer between canola (Brassica napus L. and B. campestris L.) and related weed species

Summary. Brassica species are particularly receptive to gene transformation techniques. There now exists canola genotypes with transgenic herbicide resistance for glyphosate, imidazolinone, sulfonylurea and glufosinate herbicides. The main concern of introducing such herbicide resistance into commercial agriculture is the introgression of the engineered gene to related weed species. The potential of gene transfer between canola (Brassica napus and B. campestris) and related weed species was determined by hand pollination under controlled greenhouse conditions. Canola was used as both male and female parent in crosses to the related weed species collected in the Inland Northwest region of the United States. Weed species used included: field mustard (B. rapa), wild mustard (S. arvensis) and black mustard (B. nigra). Biological and cytological aspects necessary for successful hybrid seed production were investigated including: pollen germination on the stigma; pollen tube growth down the style; attraction of pollen tubes to the ovule; ovule fertilisation; embryo and endosperm developmental stages. Pollen germination was observed in all 25 hybrid combinations. Pollen tubes were found in the ovary of over 80% of combinations. About 30% of the hybrid combinations developed to the heart stage of embryo development or further. In an additional study involving transgenic glufosinate herbicide resistant B. napus and field mustard it was found that hybrids occurred with relatively high frequency, hybrids exhibited glufosinate herbicide resistance and a small proportion of hybrids produced self fertile seeds. These fertile plants were found to backcross to either canola or weed parent.

Gibberellins in Embryo-Suspensor of Phaseolus coccineus Seeds at the Heart Stage of Embryo Development

Gibberellins (GAs) in suspensors and embryos of Phaseolus coccineus seeds at the heart stage of embryo development were analyzed by combined gas chromatography-mass spectrometry (GC-MS). From the suspensor four C(19)-GAs, GA(1), GA(4), GA(5), GA(6), and one C(20) GA, GA(44), were identified. From the embryo, five C(19)-GAs GA(1), GA(4), GA(5), GA(6), GA(60) and two C(20) GAs, GA(19) and GA(44) were identified. The data, in relation to previous results, suggest a dependence of the embryo on the suspensor during early stages of development.

Light and electron microscopy of embryo development in an annual × perennial Medicago species cross

Using light and transmission electron microscopy, we studied embryo development from 3 to 14 days after pollination in an interspecific Medicago cross (perennial M. sativa L., 2n = 4x = 32 × annual M. scutellata (L.) Mill, 2n = 4x = 32) to determine factors contributing to abortion in wide crosses. An intraspecific M. sativa cross and an M. sativa self-mating were used for control embryos. Nucellus and integumentary tapetum at the base of the embryo sac appear to be important sources of nutrition during the first 2 weeks of embryo development. Micrographic evidence supports the conclusions that maternal and embryonic tissue of interspecific ovules fail to carry out a timely sequence of metabolism involving lipid, starch, and nucellar crystals. Delayed breakdown of starch and lipid in the integumentary tapetum and nucellus is a probable factor in reduced development of coenocytic endosperm. At the late heart stage of embryo development, relative inactivity of dictyosomes and endoplasmic reticulum in hybrid ovules suggests failure of nutrient metabolism and transport in all nutritive tissue including the nucellus, integumentary tapetum, endosperm, and suspensor of the embryo. Early embryo development in Medicago appears to be a complex phenomenon requiring a high degree of coordination between anabolism and catabolism in both maternal and embryonic tissue.

Embryogeny of Phaseolus: the Role of the Suspensor

Summary Label 14 C-sucrose is administered to the developing embryos via the base of the excised pod, through the endosperm cavity of the seeds, and directly to the excised embryos. The results indicate that the suspensor is the uptake site during early stages of embryo development. When labeled solution is introduced into the endosperm cavity at the late heart stage of embryo development, radioactivity appears in the suspensor and the suspensor end of the embryo-proper. This labeling pattern is unexpected. One might have expected the cotyledonary half of the embryoproper to be more heavily labeled since it is nearer to the endosperm — the source of radioactivity. The uptake of 14 C-sucrose by the suspensor at the late heart stage is sensitive to dinitrophenol whereas the total radioactivity in the embryo-proper increases gradually with time and the uptake of 14 C-sucrose is not inhibited by the presence of dinitrophenol. The uptake pattern is changed at the mid-maturation stage. It appears that the cotyledons become the major uptake site for the maturing embryo. The results are discussed in relation to the current hypotheses of suspensor function.

Embryogeny of Phaseolus coccineus: The Suspensor and the Growth of the Embryo-Proper in vitro

In in vitro embryo culture of Phaseolus coccineus, the presence of the suspensor stimulates the growth of the embryo-proper and resulted in a higher number of plantlets when the embryo is cultured at the heart stage. The effect of the suspensor is stage specific; it has very little effect when the embryo-proper reaches the cotyledon stage. These results are in accord with the structural studies (Yeung And Clutter, 1978a, b). Detail structural ontogenetic studies indicate that the suspensor is a very specialized organ and its activity is maximal during the heart stage of embryo development. GA 3 , is the most effective growth substance when it is substituted for the suspensor, however, ABA may also play a regulatory role in the growth of embryos. The results are discussed in relation to the current hypotheses of suspensor function.

Physiology of sexual reproduction: III. Histochemical characteristics of suspensor during embryo development in Brassica campestrisLinn.Var., Sarson.

The development of suspensor in Brassica campestris is of the "Onagrad type"; The suspensor growth was maximum between the globular and heart stage of embryo development. There after, the suspensor diminished and immediately after the torpedo stage, it degenerated several enzymes (e.g. acid-, alkaline-, adenosine triphosphatase, peroxidase, succinate dehydrogenase, cyotchrome oxidase) and general substances (ascorbic acid, polysaccharides, lipids) were localized in the suspensor during different phases of embryo growth. Between the globular and heartshaped stage, suspensor cells had strong reaction. An attempt is made to elucidate possible physiological functions in relation to specific enzyme localization. The possibility of suspensor having secretory function is also brought out. Present histochemical data indicated that suspensor was chiefly concerned with absorption and transport of metabolites from the surrounding tissue to the developing embryo.

Ultrastructural characteristics of « Diplotaxis erucoides (L.) DC. » suspensor

Abstract The development and general morphology of Diplotaxis erucoides (L.) DC. suspensor is of the « Onagrad Type », « Alyssum Variation ». Maximum growth of the suspensor occurs from the globular to the early heart stage of embryo development. The suspensor starts then to degenerate disintegrating shortly after the torpedo stage of the embryo. The wall ingrowths of the long, tapering, basal cell are especially abundant at the cell's micropilar pole which is closely surrounded by well developed wall ingrowths formed by the endosperm. Wall ingrowths and plasmodesmata are present on the suspensor cells cross walls with the exception of the cell closest to the embryo. No such structures in fact are present on the walls separating this last cell both from the embryo and from the rest of the suspensor. Wall ingrowths are generally associated with numerous, large, mitochondria. The morphological data seem to indicate that absorption and transport of nutrients from the surrounding tissues is a main function of...