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G A Galau

Publications and source records attributed to G A Galau.

At least 19 recordsLinked to original sources
PubMed1997

Changes in late-embryogenesis-abundant (LEA) messenger RNAs and dehydrins during maturation and premature drying of Ricinus communis L. seeds.

In Ricinus communis L. (castor bean) endosperms, two classes of Late Embryogenesis Abundant (Lea) transcripts were first detected during mid-development (at 30-35 days after pollination, DAP) and peaked at 50 DAP, just prior to the onset of desiccation. Most of the Class I mRNAs declined substantially during desiccation itself; Class II mRNAs remained abundant in the mature dry (60 DAP) seed. Following imbibition, all Lea mRNAs abundant in the mature dry seed declined rapidly (within 5-24 h). Premature drying of developing 35-DAP seeds resulted in the loss of storage-protein mRNAs (Leg B Mat I); following rehydration, mRNAs encoding post-germinative proteins (Germ D91, D30 and D38) increased in the endosperm. The Lea mRNAs present in the developing fresh seed at 35 DAP were preserved, but did not increase in response to premature desiccation; upon rehydration these Lea mRNAs declined within 5 h. During seed development, substantial changes occurred in the synthesis of a subset of LEA proteins referred to as "dehydrins'; in particular, new dehydrin polypeptides were induced between 40 and 60 DAP. Such proteins were not as evident in prematurely dried endosperms. In contrast to the rapid loss of Lea mRNAs during germination, many of the dehydrin proteins abundant in the dried seed persisted following imbibition or rehydration.

Ricinus communis↗
PubMed1994

Simultaneous induction of postabscission and germination mRNAs in cultured dicotyledonous embryos.

Cloned mRNAs identify three programs of gene expression in cotton (Gossypium hirsutum L.) embryos that are associated with the maturation (reserve accumulation) stage, the postabscission stage, which is marked by expression of Late-embryogenesis-abundant (Lea) mRNAs, and germination (broadly defined as including all events through early postgerminative growth). In order to test if the regulation of these programs is the same in other dicotyledonous species, their expression was studied in normal and cultured maturation-stage, postabscission-stage, and mature embryo-stage embryos or seed of oilseed rape (Brassica napus L.), soybean (Glycine max [L.] Merr.), and tobacco (Nicotiana tabacum L.) using cotton and other cDNA probes. During postabscission, Lea mRNAs accumulated in all test species and were induced in earlier maturation-stage embryos by excision and culture on basal medium. Abscisic acid often enhanced this induction in the test species. Germination-specific mRNAs were induced in cultured maturation-stage and postabscission-stage embryos of all test species. These results indicate that the regulation of embryonic and germination programs is similar in all dicotyledons tested. Because excised embryos simultaneously induced postabscission and germination programs, the effects of exogenous growth regulators and other factors on such embryos probably reflect stress responses of germinating mature embryos rather than the identity of endogenous regulators of embryogenesis.

Abscisic Acid↗
PubMed1992

Late embryogenesis-abundant genes encoding proteins with different numbers of hydrophilic repeats are regulated differentially by abscisic acid and osmotic stress.

The late embryogenesis-abundant (Lea) genes, which are suggested to act as desiccation protectants during seed desiccation and in water-stressed seedlings, can be induced by abscisic acid (ABA) and various kinds of water-related stress. Using cotton Lea cDNAs as probes it was found that several of the Lea genes are conserved at the mRNA level in dicots and monocots. By screening a barley cDNA library with a cotton Lea D19 cDNA a family of three members was isolated. The putative B19 proteins have strong similarities to the Em protein in wheat and to LEA proteins from several dicots. However, the middle part of the B19 proteins consists of a 20-amino acid motif repeated three and four times in B19.3 and B19.4, respectively, but only once in B19.1. The gene products are strongly hydrophilic, the internal 20-amino acid motif being the most hydrophilic part. This motif is found once in cotton Lea D19 but is repeated twice in cotton Lea D132, indicating that the repeats are universal among monocot and dicot B19-like genes. The B19 genes are regulated similarly during embryo development, but to very different levels. In contrast, they are differentially regulated by ABA and various types of osmotic stress. In immature embryos all three genes are responsive to ABA and mannitol. However, B19.1 is also responsive to salt. Cold stress does not induce B19 mRNAs; only a stabilization of the transcript levels is seen. These results suggest that the responses to salt stress and exogenous ABA operate through different pathways.

Abscisic Acid↗
PubMed1991

Developmental and environmental induction of Lea and LeaA mRNAs and the postabscission program during embryo culture.

The major programs of gene expression during late embryogenesis are the muturation or reserve accumulation program and, after ovule abscission, the postabscission program that is composed largely of Lea and LeaA mRNAs that probably encode desiccation protectants. There are diverse opinions about the developmental regulators of these programs. Several candidates are evaluated here by measuring, in cultured embryos, the accumulation kinetics of cloned mRNAs specifically expressed in the normal maturation, postabscission, or germination programs of cotton. Maturation-stage embryos both terminate the maturation program and induce the postabscission program after excision and culture, just as they do later in the plant after ovule abscission. However, they also induce simultaneously the germination program and are thus different from any normal stage of embryo development or germination. The developmental induction of the postabscission program in culture does not require exogenous abscisic acid, but its expression is enhanced by precocious desiccation or culture on abscisic acid or high osmoticum, probably by an environmentally responsive mechanism that normally operates during germination. Normal desiccation does not control any of these programs because the embryo acquires all of the characteristics of a mature embryo before it desiccates. These and other results suggest regulation of normal embryogenesis by a maternal maturation factor, a postabscission factor, and the postabscission program.

Abscisic Acid↗
PubMed1989

Temporally modular gene expression during cotyledon development.

The regulation of cotton embryogenesis has been addressed by measuring the abundance of 47 mRNAs in cotyledons from the late cotyledon stage through early germination. There are at least 11 distinct classes of coordinately expressed mRNAs. Their expression patterns appear to result from unique combinations of five temporal abundance components. These are associated with the cotyledon stage, the endogenous concentration of free abscisic acid, maturation (reserve accumulation), ovule abscission, and germination. This modularity suggests that only a few global regulatory factors orchestrate gene expression with many genes responding to several of them. Significant expression associated only with postabscission or free abscisic acid is restricted to that of the Lea mRNAs earlier suggested to be a component of the embryo's preparation for desiccation.

Cloning, Molecular↗
PubMed1988

Restriction fragment length polymorphisms in diploid and allotetraploid Gossypium: assigning the late embryogenesis-abundant (Lea) alloalleles in G. hirsutum.

We have determined the copy number of 21 genes in an allotetraploid and several diploid species of cotton by gel and dot blot hybridization with cloned cDNAs. The legumin A, legumin B, and all 18 unique Lea (late embryogenesis-abundant) cDNA sequences isolated from the AD allotetraploid Gossypium hirsutum are present in one copy in A, D, E, and F diploid species and in two copies in G. hirsutum. Gel blot analysis of DNAs digested with EcoRI or BamHI usually detects different sized fragments in A and D diploids. Conservation of these restriction fragment length polymorphisms in G. hirsutum allows most of these fragments to be assigned to their respective subgenomes. Furthermore, both subgenomes in G. hirsutum can be distinguished from those in the interfertile allotetraploid G. barbadense. These results show that physical mapping of both sets of chromosomes in an allotetraploid should be possible by segregation analysis.

Alleles↗
PubMed1988

Allopolyploidy in bryophytes: Multiple origins of Plagiomnium medium.

Bryophytes are thought to be unique among land plants in lacking the important evolutionary process of allopolyploidy, which involves interspecific hybridization and chromosome doubling. Electrophoretic data show, however, that the polyploid moss Plagiomnium medium is an allopolyploid derivative of Plagiomnium ellipticum and Plagiomnium insigne, that P. medium has originated more than once from these progenitors, and that cross-fertilization results in interlocus genetic recombination. Evidence from restriction fragment length polymorphisms in chloroplast DNA implicates P. insigne as the female parent in interspecific hybridizations with P. ellipticum. Contrary to prevailing views, it appears that those evolutionary processes responsible for genetic differentiation and speciation in other land plants occur in the bryophytes as well.

Journal Article↗
PubMed1987

Accumulation kinetics of cotton late embryogenesis-abundant mRNAs and storage protein mRNAs: coordinate regulation during embryogenesis and the role of abscisic acid.

The accumulation of total RNA transcripts of 18 late embryo-abundant (Lea) gene families, each encoding two closely related Lea mRNAs, was measured in cotyledon total RNA during embryogenesis and germination of Gossypium hirsutum L. by RNA dot hybridization. Transcript abundance of the three storage protein families was also followed. The Lea mRNAs belong to only two related groups of commonly regulated mRNAs. The transcript level of each of the 6 members of Class I has two transient maxima during early maturation and a maximum level at 3 days prior to desiccation. The transcript level of each of the 12 members of Class II increases abruptly in late maturation with a maximum concentration at 3 days before desiccation (Class IIA) or at desiccation (Class IIB). Several patterns of early accumulation also exist within Class II, some overlapping with those of storage protein or Lea Class I mRNAs. The concentrations of Lea mRNAs increase at least 10- to 1700-fold during embryogenesis and decline 15- to 220-fold during the first day of germination. Earlier studies indicated that most Lea mRNAs, but no storage protein mRNAs, are induced in excised embryos exposed to abscisic acid (ABA). Free (+)ABA was measured during embryogenesis using a monoclonal antibody-based ELISA. The ABA concentration shows maxima correlating with the maxima in early Class I Lea mRNA abundance. However, ABA declines during the accumulation of Class I and Class II Lea mRNAs in late embryogenesis. Consequently, ABA could be an endogenous regulator of Class I Lea mRNAs during early maturation but is not the primary regulator of Lea mRNAs during late maturation. In contrast, cotyledon water potential exhibits a decrease that correlates with the late induction of Lea mRNAs. These findings are consistent with the hypothesis that low water potential is the endogenous regulator of some ABA-inducible mRNAs. The cessation of vascular flow to the embryo may also be involved in the disappearance of storage protein mRNAs and the late induction of Lea mRNAs.

Abscisic Acid↗
PubMed1987

Coordinate accumulation of homeologous transcripts of seven cotton Lea gene families during embryogenesis and germination.

One of two related patterns of total transcript accumulation are seen during embryogenesis for 18 cotton Lea (Late embryogenesis-abundant) gene families in the allotetraploid cotton Gossypium hirsutum L. cv Coker 201. Coordinate accumulation in each class is complex, suggesting that Lea mRNA abundance is regulated by several events. Each of the Lea gene families probably contains two active homeologous genes (alloalleles), one in each of cotton's two subgenomes. It is of interest whether both transcripts of a Lea family are regulated the same or whether the complexity of total transcript accumulation is due to different regulation of the two transcripts. The two polypeptides encoded by the homeologous transcripts of 7 Lea families can be distinguished on two-dimensional gels. The majority of Lea transcripts in total RNAs is shown to be functional in vitro throughout development; thus in vitro translation should faithfully measure their relative abundance. The ratio of the two transcripts of each was followed during embryo maturation when Lea transcript concentration increases an average of 70-fold and during the first 12 hr of germination when Lea transcripts decline in concentration an average of 50-fold. For 6 of the Lea families, the relative level of the two transcripts is invariant throughout this period. The two constituent transcripts of the seventh, Lea9, change 5-fold in relative concentration during late maturation and 3-fold during germination. Both transcripts still follow the same temporal pattern of accumulation; only their rates of change are somewhat different. These Lea families are a random sample of the 18 described. If multiple events affect the mRNA abundance of each Lea family, such events then each affect their individual transcripts in a similar way.

Alleles↗
PubMed1984

Addition of proteins to the cylindrical gel embedding medium for transverse molecular-weight markers in two-dimensional gel electrophoresis.

As an aid in the comparison of different complex mixtures of proteins resolved by two-dimensional electrophoresis, a simple method which results in the electrophoresis of molecular-weight standards as appropriately migrating, highly resolved bands extending across the entire second-dimension slab gel is described. The proteins to be used as markers are included in the molten agarose mixture used to affix the first-dimension cylindrical gel atop the second-dimension slab gel. As the proteins which are resolved in the first dimension migrate through the second-dimension slab gel, the marker proteins also migrate, experiencing the same electrophoretic conditions as the sample proteins in the immediate vicinity. If the same protein is resolved in the first dimension and also used as a marker, it electrophoreses in the second dimension as a spot intersected by a band traversing the entire gel. This sensitive method is applied to a comparison of soluble seed proteins of two cotton species, Gossypium hirsutum and G. arboreum, using G. hirsutum seed protein as the molecular-weight marker. Other applications are described.

Electrophoresis, Polyacrylamide Gel↗
PubMed1983

Rapid preparation of vector-free hybridization probes suitable for screening recombinant libraries.

A procedure is described to rapidly prepare radioactively labeled DNA inserts from crude recombinant plasmid DNA preparations. These probes can subsequently be used to identify homologous nucleotide sequences in bacteria containing recombinant plasmids by colony hybridization. In a single procedure, crude recombinant plasmid DNA is both 32P-labeled and fragmented by nick-translation in the presence of sufficient pancreatic DNase I to produce radioactive DNA of about 0.2-0.3-kb single-strand length. At this DNA fragment length the majority of the vector and insert sequences are on different DNA fragments. The insert DNA can then be separated from vector and contaminating Escherichia coli host chromosomal DNA by the following method. The DNA fragment population is first denatured and renatured under conditions such that the recombinant plasmid DNA reassociates but host DNA does not. The renatured plasmid DNA fragments are separated from the denatured host DNA by hydroxylapatite chromatography. The plasmid DNA fragments are then denatured and renatured with an excess of insert-free vector DNA. Conditions are chosen such that the insert DNA remains single-stranded while the vector DNA becomes double-stranded. The single-stranded insert DNA can be separated from the double-stranded vector DNA on hydroxylapatite and used directly for colony hybridization.

DNA, Recombinant↗