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M Espelund

Publications and source records attributed to M Espelund.

7 recordsLinked to original sources
PubMed2000

A molecular genetic analysis of Eragrostis tef (Zucc.) Trotter: non-coding regions of chloroplast DNA, 18S rDNA and the transcription factor VP1.

The non-coding chloroplast DNA sequences of the trnL (UAA) intron and the trnL-trnF (GAA) intergeneric spacer (IGS), the coding sequences of nuclear 18S rDNA, and the transcription factor Vp1 of the cereal tef (Eragrostis tef (Zucc.) Trotter) were studied. No intraspecific variation was found among the 6 studied tef varieties. However, the study displayed that Eragrostis tef has a number of unique traits compared to other grasses. Phylogenetic analysis of the chloroplast DNA gave three grass clades, joining Eragrostis with sorghum and maize in one. In the analysis of the 18S rDNA sequences, the three grass species were joined in a monophyletic trichotomy in the cladogram, in which maize is the most divergent, rice the least and tef intermediate. The Vp1 is highly conserved. The Vp1 phylogeny showed that the tef Vp1-sequence is the hitherto most divergent Vp1-sequence reported from a grass.

Amino Acid Sequence↗
PubMed1997

Developmental, stress and ABA modulation of mRNA levels for bZip transcription factors and Vp1 in barley embryos and embryo-derived suspension cultures.

The transcription factors VP1 (Viviparous-1), EmBP-1 (Em-binding protein 1) and OSBZ8, originally cloned and analysed in various monocot species, have been implicated in the regulation of the Lea (late embryogenesis-abundant) group 1 genes. We have investigated the modulation of the levels of these mRNAs in barley during embryogenesis, and in developing embryos subjected to various kinds of osmotic stress. The accumulation of mRNA for VP1 and EmBP-1 transcription factors, using cDNAs cloned from barley, starts at 10 and 15 days after anthesis, respectively, whereas Lea B19 mRNA levels are very low or undetectable until 25 days after anthesis during normal development. The EmBP-1 mRNA is predominantly induced in mannitol-stressed immature embryos. Vp1 mRNA was not significantly modulated by ABA, salt or mannitol. Inhibition of ABA biosynthesis by norflurazon showed that the induction of both Vp1 and EmBP-1 mRNAs was ABA-independent. In embryo-derived suspension-cultured cells, neither of the two transcripts would be induced by ABA or osmotic stress, although both OSBZ8 and one member of the Lea B19 family was up-regulated by ABA. Electrophoretic mobility shift assays using a Lea B19.1 probe with an ABRE (abscisic acid-responsive element) similar to that which binds EmBP-1 and OSBZ8 in the wheat and rice Em promoters show that the binding activity is increased by ABA and osmotic stress. Taken together, these data show that both VP1 and EmBP-1 are involved in embryo-specific signal transduction pathways, that they are differentially regulated at the mRNA level, and that EmBP-1 can be induced by osmotic stress independently of any increase in endogenous ABA. The difference in mRNA regulation patterns of OSBZ8 and EmBP-1 may suggest that they are involved in different signal transduction pathways in connection with osmotic stress/ABA regulation of Lea genes.

Abscisic Acid↗
PubMed1995

Evolution of the Group 1 late embryogenesis abundant (Lea) genes: analysis of the Lea B19 gene family in barley.

The highly conserved Group 1 late embryogenesis abundant (Lea) genes are present in the genome of most plants as a gene family. Family members are conserved along the entire coding region, especially within the extremely hydrophilic internal 20 amino acid motif, which may be repeated. Cloning of Lea Group 1 genes from barley resulted in the characterization of four family members named B19.1, B19.1b, B19.3 and B19.4 after the presence of this motif 1, 1, 3 and 4 times in each gene, respectively. We present here the results of comparative and evolutionary analyses of the barley Group 1 Lea gene family (B19). The most important findings resulting from this work are (1) the tandem clustering of B19.3 and B19.4, (2) the spatial conservation of putative regulatory elements between the four B19 gene promoters, (3) the determination of the relative 'age' of the gene family members and (4) the 'chimeric' nature of B19.3 and B19.4, reflecting a cross-over or gene-conversion event in their common ancestor. We also show evidence for the presence of one or two additional expressed B19 genes in the barley genome. Based on our results, we present a model for the evolution of the family in barley, including the 20 amino acid motif. Comparisons of the relatedness between the barley family and all other known Group 1 Lea genes using maximum parsimony (PAUP) analysis provide evidence for the time of divergence between the barley genes containing the internal motif as a single copy and as a repeat. The PAUP analyses also provide evidence for independent duplications of Group 1 genes containing the internal motif as a repeat in both monocots and dicots.

Base Sequence↗
PubMed1994

Another Lea B19 gene (Group1 Lea) from barley containing a single 20 amino acid hydrophilic motif.

A new member of the Lea B19 gene family from barley, termed B19.1b, has been isolated and characterized. The coding region of B19.1b is highly similar to the other members of the B19 family (Espelund et al., Plant J 2 (1992) 241-252) and contains only one copy of the hydrophilic sequence found as a repeat in two other B19 genes. Like the other B19 genes, B19.1b is only expressed in embryos. The transcript appears during development at 25 days after anthesis and remains at a high level throughout embryogenesis. In immature embryos the B19.1b mRNA can be induced by abscisic acid, salt and mannitol.

Amino Acid Sequence↗
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↗
PubMed1992

Cloning and direct sequencing of plant promoters using primer-adapter mediated PCR on DNA coupled to a magnetic solid phase.

A method that allows amplification and direct sequencing or cloning of an unknown DNA segment flanked by a known sequence is described using barley genomic DNA. The method avoids the step of circularization necessary for inverse PCR by ligation of primer-adapters to restricted genomic DNA. Specificity is achieved in the first amplification step; linear PCR with a biotinylated primer complementary to the known flanking sequence (primer 1-B) produces a single-stranded product that is purified employing streptavidin-coated magnetic beads. After this step, which removes genomic DNA, two rounds of exponential PCR are performed, first with the adapter-primer and primer 1 and second with primer 1 substituted by a nested primer 2. If the second primer is biotinylated, the product can be sequenced directly using solid-phase sequencing. We have employed this method to sequence directly and to clone the promoters of two late embryogenesis-abundant (Lea) genes (B19.4 and B19.3) from barley. Lea B19.4 and B19.3 encode putative desiccation-protective proteins that act in the final stages of embryogenesis and have previously been cloned as cDNAs. We demonstrate here that their proximal promoter regions are very similar (80% identity) and that both contain putative abscisic acid-responsive elements.

Base Sequence↗