Late Embryogeny Research Articles

Multiple analyses of various factors affecting the plantlet regeneration of Picea mongolica (H. Q. Wu) W.D. Xu from somatic embryos

Picea mongolica, a native species with excellent industrial wood quality and strong sand-fixing capacity, may be utilized in construction of urban green spaces in arid areas in China. However, now the sustainability of the ecosystems where this species grows is at serious risk due to a lack of natural regeneration. In this study, we developed an efficient regeneration system and comprehensively analyzed various factors affecting somatic embryogenesis (SE) using zygotic embryos as explants. We identified the optimal plant growth regulators (PGRs) performance and the best donor trees (k81) for the generation of somatic embryos (SEMs). Additionally, we confirmed that the positive developmental window of SEMs initiation was at the end of July to early August, which is when zygotic embryos was at the late embryogeny. In this time period, specific transcripts associated with the regulation of epigenetic modifications, plant hormone-related genes, and embryonic development-related transcription factors play important roles for early SEMs initiation. These results may provide a valuable resource for vegetative propagation of Picea mongolica. Our results may help to establish a reliable protocol for plantlet regeneration, which may facilitate urban greening applications and industrialization in arid areas.

Recalcitrant behaviour of the seeds of Syzygium cumini (L.) Skeels during embryogeny and natural desiccation

Syzygium cumini (L.) Skeels is an indigenous, evergreen arborescent species in the Western-Ghats having multiple utilization. Though the species has been reported as recalcitrant one, the exact seed biology has not been well documented. The work mainly focussed on understanding the seed physiology during embryogeny and natural drying. The embryonal axis and cotyledons showed a tendency to import water from the maternal plant during embryogeny with higher water content in the embryos at maturity, compared to other recalcitrant embryos. No delay was observed during seed germination, the rate of drying was faster, seeds lost viability after 360 h of natural drying and the critical moisture content of the embryonal axis was found to be 27.5%. A strong positive correlation existed between the rate of seed germination and the moisture content of the embryo. Desiccation was accompanied by electrolyte leakage from the embryo due to membrane damage, an inverse relationship could be observed between moisture content and electrolyte leakage in the embryos. The growth regulator, ABA showed a peak during mid-embryogeny and then a decreasing trend in the late embryogeny in both cotyledons and axis, indicating the true recalcitrant behaviour of the seeds.

WUSCHEL-RELATED HOMEOBOX 2 is important for protoderm and suspensor development in the gymnosperm Norway spruce.

BackgroundDistinct expression domains of WUSCHEL-RELATED HOMEOBOX (WOX) gene family members are involved in patterning and morphogenesis of the early embryo in Arabidopsis. However, the role of WOX genes in other taxa, including gymnosperms, remains elusive. Here, we use somatic embryos and reverse genetics for studying expression and function of PaWOX2, the corresponding homolog of AtWOX2 in the gymnosperm Picea abies (Pa; Norway spruce).ResultsThe mRNA level of PaWOX2 was transiently up-regulated during early and late embryogeny. PaWOX2 mRNA in early and early late embryos was detected both in the embryonal mass and in the upper part of the suspensor. Down-regulation of PaWOX2 during development of early embryos resulted in aberrant early embryos, which failed to form a proper protoderm. Cells on the surface layer of the embryonal mass became vacuolated, and new embryogenic tissue differentiated from the embryonal mass. In addition, the aberrant early embryos lacked a distinct border between the embryonal mass, and the suspensor and the length of the suspensor cells was reduced. Down-regulation of PaWOX2 in the beginning of embryo development, before late embryos were formed, caused a significant decrease in the yield of mature embryos. On the contrary, down-regulation of PaWOX2 after late embryos were formed had no effect on further embryo development and maturation.ConclusionsOur data suggest an evolutionarily conserved function of WOX2 in protoderm formation early during embryo development among seed plants. In addition, PaWOX2 might exert a unique function in suspensor expansion in gymnosperms.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0706-7) contains supplementary material, which is available to authorized users.

Wuschel-related homeobox 8/9 is important for proper embryo patterning in the gymnosperm Norway spruce.

Proper embryo development is crucial as that is when the primary body axes are established. In Arabidopsis, AtWOX8 and AtWOX9, members of the Wuschel-related homeobox (WOX) gene family, are critical for embryo development. In Norway spruce, PaWOX8/9, which is expressed in embryos, is the homologue of AtWOX8 and AtWOX9. In this work, it is shown that the transcript abundance of PaWOX8/9 is high during early and late embryogeny and that it decreases when the maturation phase starts. To address the function of PaWOX8/9 during embryo development, RNAi lines were established to down-regulate the transcript level of PaWOX8/9, using both constitutive and inducible promoters. Embryos in the PaWOX8/9 RNAi lines show an aberrant morphology caused by disturbed orientation of the cell division plane at the basal part of the embryonal mass during early and late embryogeny. In addition, the transcript level of several key cell-cycle-regulating genes, for example, PaE2FAB-like and PaCYCLIN B-like, are affected in the PaWOX8/9 RNAi lines. Taken together, our results suggest that PaWOX8/9 may perform an evolutionarily conserved function as a regulator of the establishment of the apical-basal embryo pattern.

Embryogenic potential and expression of embryogenesis-related genes in conifers are affected by treatment with a histone deacetylase inhibitor

Somatic embryogenesis is used for vegetative propagation of conifers. Embryogenic cultures can be established from zygotic embryos; however, the embryogenic potential decreases during germination. In Arabidopsis, LEAFY COTYLEDON (LEC) genes are expressed during the embryonic stage, and must be repressed to allow germination. Treatment with the histone deacetylase inhibitor trichostatin A (TSA) causes de-repression of LEC genes. ABSCISIC ACID3 (ABI3) and its Zea mays ortholog VIVIPAROUS1 (VP1) act together with the LEC genes to promote embryo maturation. In this study, we have asked the question whether TSA treatment in a conifer affects the embryogenic potential and the expression of embryogenesis-related genes. We isolated two conifer LEC1-type HAP3 genes, HAP3A and HAP3B, from Picea abies and Pinus sylvestris. A comparative phylogenetic analysis of plant HAP3 genes suggests that HAP3A and HAP3B are paralogous genes originating from a duplication event in the conifer lineage. The expression of HAP3A is high, in both somatic and zygotic embryos, during early embryo development, but decreases during late embryogeny. In contrast, the expression of VP1 is initially low but increases during late embryogeny. After exposure to TSA, germinating somatic embryos of P. abies maintain the competence to differentiate embryogenic tissue, and simultaneously the germination progression is partially inhibited. Furthermore, when embryogenic cultures of P. abies are exposed to TSA during embryo maturation, the maturation process is arrested and the expression levels of PaHAP3A and PaVP1 are maintained, suggesting a possible link between chromatin structure and expression of embryogenesis-related genes in conifers.

Embryogenic potential and expression of embryogenesis-related genes in conifers are affected by treatment with a histone deacetylase inhibitor.

Somatic embryogenesis is used for vegetative propagation of conifers. Embryogenic cultures can be established from zygotic embryos; however, the embryogenic potential decreases during germination. In Arabidopsis, LEAFY COTYLEDON (LEC) genes are expressed during the embryonic stage, and must be repressed to allow germination. Treatment with the histone deacetylase inhibitor trichostatin A (TSA) causes de-repression of LEC genes. ABSCISIC ACID3 (ABI3) and its Zea mays ortholog VIVIPAROUS1 (VP1) act together with the LEC genes to promote embryo maturation. In this study, we have asked the question whether TSA treatment in a conifer affects the embryogenic potential and the expression of embryogenesis-related genes. We isolated two conifer LEC1-type HAP3 genes, HAP3A and HAP3B, from Picea abies and Pinus sylvestris. A comparative phylogenetic analysis of plant HAP3 genes suggests that HAP3A and HAP3B are paralogous genes originating from a duplication event in the conifer lineage. The expression of HAP3A is high, in both somatic and zygotic embryos, during early embryo development, but decreases during late embryogeny. In contrast, the expression of VP1 is initially low but increases during late embryogeny. After exposure to TSA, germinating somatic embryos of P. abies maintain the competence to differentiate embryogenic tissue, and simultaneously the germination progression is partially inhibited. Furthermore, when embryogenic cultures of P. abies are exposed to TSA during embryo maturation, the maturation process is arrested and the expression levels of PaHAP3A and PaVP1 are maintained, suggesting a possible link between chromatin structure and expression of embryogenesis-related genes in conifers.Electronic supplementary materialThe online version of this article (doi:10.1007/s00425-011-1418-8) contains supplementary material, which is available to authorized users.

Up, down and up again is a signature global gene expression pattern at the beginning of gymnosperm embryogenesis

Somatic embryogenesis of a gymnosperm, Picea abies, represents a sequence of specifically regulated developmental stages including proembryogenic mass (PEM), PEM-to-embryo transition, and early and late embryogeny. Here, we report cDNA array analysis of expression patterns of 373 genes in the beginning of P. abies embryo development. The analysis revealed a group of 107 genes (29% of arrayed cDNAs) which were upregulated upon PEM-to-embryo transition, then downregulated during early embryogeny and finally upregulated again at the beginning of late embryogeny. This major gene expression pattern was abrogated in a developmentally arrested cell line that is unable to pass through the PEM-to-embryo transition. Thirty-five genes (9.4% of arrayed cDNAs) were found to be differentially expressed during normal embryonic pattern formation. Among them, 22 genes (5.9% of arrayed cDNAs) were directly associated with embryo pattern formation and can be considered as marker genes for early stages of P. abies embryogenesis. The majority of the marker genes encode for proteins involved in translation and posttranslational modification. Among them, 18 genes displayed the major expression pattern.

Expression of a Brassica napus Malate Synthase Gene in Transgenic Tomato Plants during the Transition from Late Embryogeny to Germination

To study gene regulation during the transition from late embryogeny to germination, we have analyzed the expression of a gene encoding the glyoxylate cycle enzyme malate synthase in transgenic tomato (Lycopersicon esculentum) plants. We have shown that although there are at least four classes of malate synthase genes in Brassica napus L., one gene is expressed at a high level during both late embryogeny and postgermination. Analyses of transgenic tomato plants containing the expressed B. napus gene along with 4.7 and 1.0 kilobase pairs of 5' and 3' flanking sequences, respectively, confirmed that a single gene is expressed at both stages of development. Furthermore, localization studies have shown that mRNA encoded by the B. napus gene is distributed throughout the tissues of a mature embryo but is not detected in the vascular cylinder of a seedling. We conclude that the sequences required to qualitatively regulate the gene correctly over the plant life cycle are present within the transferred gene and/or flanking regions. Moreover, the malate synthase gene is regulated differently during late embryogeny and postgermination in the developing vascular cylinder.

Transcriptional activities in dry seed nuclei indicate the timing of the transition from embryogeny to germination.

To investigate processes regulating the reinitiation of growth and differentiation during seed germination, we have studied the transcriptional activities of sets of genes that are expressed at specific stages of embryogeny and post-germination in the higher plant Brassica napus L. We show that transcripts from a subset of the genes are elongated in nuclei isolated from dry seeds, indicating that these genes are competent to be transcribed in desiccated and quiescent mature embryos. Analysis of the specific transcripts produced in dry seed nuclei indicates that the changes in gene expression patterns associated with germination are not initiated during late embryogeny. The results suggest that the transition from an embryonic to a postgerminative program of development occurs after seeds are rehydrated.

Light-mediated Inhibition of in Vitro Late Embryogeny of Ilex

Abstract An inhibitory effect of light on in vitro late embyogeny of I. aquifolium and I. opaca cv. Farage was observed. A negative log-linear correlation between the final embryo size and hours of continuous light during preincubation, at an intensity of 64 W·m−2, was established with I. aquifolium. It took ≈ 15 hr of pre-incubation light to result in 50% growth inhibition. Negative log-linear correlations between the final embryo lengths and light intensities were also observed for I. aquifolium and I. opaca. The rudimentary embryos of I. opaca were more sensitive to light inhibition than those of I. aquifolium. During incubation for 11 and 14 days with a 16-hr photoperiod, light intensities for 50% growth inhibition were ≈ 5 and 11 W·m−2 for I. opaca and I. aquifolium, respectively. Since growth inhibition by light could not be reversed by the presence of GA3 concentrations up to 1000 μm, some factor(s) other than the accumulation of abscisic acid or related compounds is probably responsible for such a phenomenon.

Spatially regulated genes expressed during seed germination and postgerminative development are activated during embryogeny

We investigated the control of genes expressed primarily during seed germination and postgerminative development in Brassica napus L. We identified cloned mRNA sequences which became prevalent within 1 day after the start of imbibition and were at low or undetectable levels in immature embryos, dry seeds, and leaves. Most postgermination-abundant mRNAs accumulated primarily, though not exclusively, in different parts of the seedling. Of the 14 cloned mRNAs, 8 were prevalent in cotyledons, 2 were abundant in seedling axes, and 4 were approximately equally distributed in both parts. We showed that although these mRNAs reached maximal levels in seedlings, the spatially regulated mRNAs were also detected at distinct embryonic stages; mRNAs prevalent in seedling axes accumulated primarily during early embryogenesis while cotyledon-abundant mRNA concentration increased during late embryogeny. We conclude that the temporal and spatial regulation of gene expression in seedlings reflects similarities and differences in the physiological functions of cotyledons and axes. Furthermore, the regulated expression of cotyledon-abundant genes during late embryogeny suggests that the mRNAs and possibly proteins may accumulate in preparation for subsequent seedling growth. Similarities in the accumulation of cotyledon-abundant mRNAs may indicate coordinate regulation of this gene set.

ゴマの後期胚形成と組織分化

1) Late embryogeny and histogenesis in Sesamum indicum L. were described.2) The protoderm of the embryo is established early by the periclinal division of the cells of the 8-celled embryo-globe: the cells of the surface layer produced by this division are divided only anticlinally thereafter, except for a few cells participating in the root-cap formation.3) The tissue differentiation in the embryo starts with the appearance of cells with decreased stainability. The first such cells appear in the outer ground meristem, which makes the embryonic cortex, then follows the appearance of such cells in the inner ground meristem, which makes the pith in the hypocotyl. In consequence of the appearance of these less-staining regions, tissues whose cells are dark-staining and appear unaltered are blocked out as a procambial core and a presumptive region of cotyledons and plumule. The procambial core differentiates into the embryonic stele.4) The presumptive region of cotyledons and plumule is regarded as an incipient, juvenile shoot apex. The shoot apex develops from the juvenile to the advanced structure through embryogeny. Even in the full-grown embryo, however, the apical meristem remains incompletely developed. No periclinal division occurs in the 2nd or 3rd cell layer at the leaf position prior to the formation of the first foliage leaves. This makes a contrast with the initiation of later leaves, which is preceded by periclinal divisions in the 2nd and 3rd layers. The apical meristem is connected with the procambium of the hypocotyl by two meristematic strands at opposite sides of the procambial cylinder in the intercotyledonary plane before the first leaf primordia are initiated.5) The apical meristem of the radicle is organized at about the same stage with the cotyledons, earlier than the formation of the plumule. Initials of the root cortex and those of the epidermis and root-cap are distinguished from other cells, from the time of their very origin. The undermost cells of the procambial core, which are contiguous with the cortex initials, function as the initials of the root stele.6) The embryonic stele is differentiated as a structure having the transitional pattern of vascular system between the cotyledons and the root: its fundamental tissue pattern is already determined when the first protoxylem and protophloem poles appear.

INVESTIGATIONS OF PERMEABILITY, DIAPAUSE, AND HATCHING IN THE EGGS OF THE MOSQUITO AEDES HEXODONTUS DYAR

Methods for collection in the laboratory of many thousands of eggs from field-collected, blood-fed females are described. Also a way of separating fertile from infertile eggs is outlined. When the eggs are laid they are white but begin to darken within one-half hour. The darkening did not occur when the egg cell or early embryo was killed.Two changes in permeability in the prediapause stage of the eggs of Aedcs hexodontus were observed. The first took place as the chorion changed from white to black. The egg lost and gained water easily when first laid but resisted water loss and uptake as the chorion darkened. However, a complete waterproofing did not result. With the formation of the transparent cuticle a further change in permeability occurred. The egg lost hardly any water even when exposed to extreme desiccation and what little water was lost was regained very slowly. However, the cuticle, with the chorion removed in sodium hypochlorite, was quite permeable. The impermeability of the chorion and cuticle combination must result from the bonding between the two and this bonding must be disrupted by the dechorionation.To study the obligate diapause that occurs in the late embryogeny of the mosquito egg the effect of making water available to the embryo, of light, and of low temperature was studied. Diapause was not broken when water was available to the embryo, nor did alternate periods of light and dark at room temperature or at lower temperatures disrupt the diapause. To test the influence of cold the temperature of 1° and −3 °C. were used to simulate the temperatures in the field. The low temperatures were found to terminate the diapause but the numbers of eggs hatching did not steadily increase with an increase in the time of exposure to cold. No clue has as yet been discovered to explain these results. A hatching infusion of decaying adult mosquito bodies in distilled water was found to give more hatching than did distilled water alone. The mechanism of the hatching stimulus is not known.

Late Embryogeny and Histogenesis in Pisum

Late Embryogeny and Histogenesis in Pisum

EMBRYOGENY AND THE DEVELOPMENT OF THE APICAL MERISTEMS OF PSEUDOTSUGA. II. LATE EMBRYOGENY

American Journal of BotanyVolume 34, Issue 2 p. 73-80 Article EMBRYOGENY AND THE DEVELOPMENT OF THE APICAL MERISTEMS OF PSEUDOTSUGA. II. LATE EMBRYOGENY George S. Allen, George S. Allen Department of Forestry, University of British Columbia, Vancouver, B. C.Search for more papers by this author George S. Allen, George S. Allen Department of Forestry, University of British Columbia, Vancouver, B. C.Search for more papers by this author First published: 01 February 1947 https://doi.org/10.1002/j.1537-2197.1947.tb12960.xCitations: 19AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume34, Issue2February 1947Pages 73-80 RelatedInformation

11. A Systematic Study of the Main Arteries in the Region of the Heart. Aves: Piciformes*

Summary.Eight species of Ramphastidæ, 11 species of Capitonidæ, six species of Bucconidæ, two species of Indicatoridæ, and 45 species of Picidæ were studied, and descriptions with diagrams of the main arteries in the region of the neck and thorax prepared. Suggestive differences in the arrangement‐patterns of the arteries were recorded with reference to the basic Order pattern and the Family variation. Presence of the ligamentous vestiges of the left radix aortæ, right ductus botalli, and right ductus caroticus were noted along with the presence of a patent ductus caroticus in Dryobates v. villosus. Possible phyletic relationships between other orders of birds were indicated by the arterial arrangement. All families of the Picidæ were found to be “laevo‐carotidinæ” whereas in the Coraciiformes some families were “lævo‐carotidinæ” while others were “bicarotidinæ normales.” The ductus shawi was shown to be the functionally modified ductus caroticus and was found to be a vessel which results from anastomoses with other smaller arteries which form in situ during middle to late embryogeny. The tendency for a large number of anastomoses of major embryonic vessels, with a few pertinent examples, was noted.