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R. B. Goldberg

Publications and source records attributed to R. B. Goldberg.

8 recordsLinked to original sources
PubMed1994

Cell Differentiation and Morphogenesis Are Uncoupled in Arabidopsis raspberry Embryos.

We identified two Arabidopsis embryo mutants, designated as raspberry1 and raspberry2, by screening T-DNA-mutagenized Arabidopsis lines. Embryogenesis in these mutants is indistinguishable from that of wild-type plants until the late-globular stage, after which raspberry1 and raspberry2 embryos fail to undergo the transition to heart stage, remain globular shaped, and proliferate an enlarged suspensor region. raspberry1 and raspberry2 embryo-proper regions enlarge during embryogenesis, become highly vacuolate, and display prominent convex, or "raspberry-like" protuberances on their outer cell layers. In situ hybridization studies with several embryo cell-specific mRNA probes indicated that the raspberry1 and raspberry2 embryo-proper regions differentiate tissue layers in their correct spatial contexts and that the regulation of cell-specific genes within these layers is normal. Surprisingly, a similar spatial and temporal pattern of mRNA accumulation occurs within the enlarged suspensor region of raspberry1 and raspberry2 embryos, suggesting that a defect in embryo-proper morphogenesis can cause the suspensor to take on an embryo-proper-like state and differentiate a radial tissue-type axis. We conclude that cell differentiation can occur in the absence of both organ formation and morphogenesis during plant embryogenesis and that interactions occur between the embryo-proper and suspensor regions.

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PubMed1994

LEAFY COTYLEDON1 Is an Essential Regulator of Late Embryogenesis and Cotyledon Identity in Arabidopsis.

LEAFY COTYLEDON1 (LEC1) is an embryo defective mutation that affects cotyledon identity in Arabidopsis. Mutant cotyledons possess trichomes that are normally a leaf trait in Arabidopsis, and the cellular organization of these organs is intermediate between that of cotyledons and leaves from wild-type plants. We present several lines of evidence that indicate that the control of late embryogenesis is compromised by the mutation. First, mutant embryos are desiccation intolerant, yet embryos can be rescued before they dry to yield homozygous recessive plants that produce defective embryos exclusively. Second, although many genes normally expressed during embryonic development are active in the mutant, at least one maturation phase-specific gene is not activated. Third, the shoot apical meristem is activated precociously in mutant embryos. Fourth, in mutant embryos, several genes characteristic of postgerminative development are expressed at levels typical of wild-type seedlings rather than embryos. We conclude that postgerminative development is initiated prematurely and that embryonic and postgerminative programs operate simultaneously in mutant embryos. The pleiotropic effects of the mutation indicate that the LEC1 gene plays a fundamental role in regulating late embryogenesis. The role of LEC1 and its relationship to other genes involved in controlling late embryonic development are discussed.

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PubMed1993

To Teach or Not.

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PubMed1992

Having an Impact.

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PubMed1990

From the Editor.

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PubMed1990

Different Temporal and Spatial Gene Expression Patterns Occur during Anther Development.

We studied the temporal and spatial regulation of three mRNA sequence sets that are present exclusively, or at elevated levels, in the tobacco anther. One mRNA set accumulates in the tapetum and decays as the tapetum degenerates later in anther development. The second mRNA set accumulates after the tapetal-specific mRNAs, is localized within the stomium and connective, and also decays as these cell types degenerate during anther maturation. The third mRNA sequence set persists throughout anther development and is localized within most anther tissues. A tapetal-specific gene, designated as TA29, was isolated from a tobacco genome library. Runoff transcription studies and experiments with chimeric [beta]-glucuronidase and diphtheria toxin A-chain genes showed that the TA29 gene is regulated primarily at the transcriptional level and that a 122-base pair 5[prime] region can program the tapetal-specific expression pattern. Destruction of the tapetum by the cytotoxic gene had no effect on the differentiation and/or function of surrounding sporophytic tissues but led to the production of male-sterile plants. Together, our studies show that several independent gene expression programs occur during anther development and that these programs correlate with the differentiated state of specific anther cell types.

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PubMed1989

Soybean Seed Protein Genes Are Regulated Spatially during Embryogenesis.

We used in situ hybridization to investigate Kunitz trypsin inhibitor gene expression programs at the cell level in soybean embryos and in transformed tobacco seeds. The major Kunitz trypsin inhibitor mRNA, designated as KTi3, is first detectable in a specific globular stage embryo region, and then becomes localized within the axis of heart, cotyledon, and maturation stage embryos. By contrast, a related Kunitz trypsin inhibitor mRNA class, designated as KTi1/2, is not detectable during early embryogenesis. Nor is the KTi1/2 mRNA detectable in the axis at later developmental stages. Outer perimeter cells of each cotyledon accumulate both KTi1/2 and KTi3 mRNAs early in maturation. These mRNAs accumulate progressively from the outside to inside of each cotyledon in a "wave-like" pattern as embryogenesis proceeds. A similar KTi3 mRNA localization pattern is observed in soybean somatic embryos and in transformed tobacco seeds. An unrelated mRNA, encoding [beta]-conglycinin storage protein, also accumulates in a wave-like pattern during soybean embryogenesis. Our results indicate that cell-specific differences in seed protein gene expression programs are established early in development, and that seed protein mRNAs accumulate in a precise cellular pattern during seed maturation. We also show that seed protein gene expression patterns are conserved at the cell level in embryos of distantly related plants, and that these patterns are established in the absence of non-embryonic tissues.

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