Biomedical subjects

G Leubner-Metzger

Publications and source records attributed to G Leubner-Metzger.

4 recordsLinked to original sources

PubMed1999

Distinct ethylene- and tissue-specific regulation of beta-1,3-glucanases and chitinases during pea seed germination.

The expression of beta-1,3-glucanase (betaGlu) and chitinase (Chn) was investigated in the testa, cotyledons, and embryonic axis of germinating Pisum sativum L. cv. 'Espresso generoso' seeds. High concentrations of betaGlu and Chn activity were found in the embryonic axis. Treatment with ethylene alone or in combination with the inhibitor of ethylene action 2,5-norbornadiene showed that an early, 4-fold induction of betaGlu activity in the embryonic axis during the first 20 h after the start of imbibition is ethylene-independent. This initial increase was followed by a later 4-fold ethylene-dependent induction in the embryonic axis starting at 50 h, which is after the onset of ethylene evolution and after completion of radicle emergence. The betaGlu activity in cotyledons increased gradually throughout germination and was ethylene-independent. In contrast, the ethylene-independent Chn activity increased slightly after the onset of radical emergence in the embryonic axis and remained at a constant low level in cotyledons. Immunoinactivation assays and immunoblot analyses suggest that early betaGlu activity in the embryonic axis is due to a 54-kDa antigen, whereas late induction is due to a 34.5-kDa antigen, which is likely to be the ethylene-inducible class I betaGlu G2 described for immature pea pods. Increases in Chn in the embryonic axis were correlated with a 26-kDa antigen, whereas amounts of the additional 32- and 20-kDa antigens remained roughly constant. Thus, ethylene-dependent and ethylene-independent pathways regulate betaGlu and Chn during pea seed germination. The pattern of regulation differs from that of leaves and immature pods, and from that described for germinating tobacco seeds. The functional significance of this regulation and its underlying mechanisms are discussed.

Journal Article↗

PubMed1998

Ethylene-responsive element binding protein (EREBP) expression and the transcriptional regulation of class I beta-1,3-glucanase during tobacco seed germination.

Class I beta-1,3-glucanase (betaGLU I) is transcriptionally induced in the micropylar endosperm just before its rupture prior to the germination (i.e. radicle emergence) of Nicotiana tabacum L. cv. 'Havana 425' seeds. Ethylene is involved in endosperm rupture and high-level betaGLU I expression; but, it does not affect the spatial and temporal pattern of betaGLU I expression. A promoter deletion analysis of the tobacco betaGLU I B gene suggests that (1) the distal - 1452 to - 1193 region, which contains the positively acting ethylene-responsive element (ERE), is required for high-level, ethylene-sensitive expression, (2) the regions - 1452 to - 1193 and -402 to 0 contribute to downregulation by abscisic acid (ABA), and (3) the region -402 to -211 is necessary and sufficient for low-level micropylar-endosperm-specific expression. Transcripts of the ERE-binding proteins (EREBPs) showed a novel pattern of expression during seed germination: light or gibberellin was required for EREBP-3 and EREBP-4 expression; EREBP-4 expression was constitutive and unaffected by ABA or ethylene; EREBP-3 showed transient induction just before endosperm rupture, which was earlier in ethylene-treated seeds and inhibited by ABA. No expression of EREBP- and EREBP-2 was detected. In contrast to betaGLU I, EREBP-3 and EREBP-4 were not expressed specifically in the micropylar endosperm. The results suggest that transcriptional regulation of betaGLU I could depend on: activation of ethylene signalling pathways acting via EREBP-3 with the ERE as the target, and ethylene-independent signalling pathways with targets in the proximal promoter region that are likely to determine spatial and temporal patterns of expression.

Abscisic Acid↗

PubMed1997

Latex allergen database.

Two-dimensional (2-D) electrophoresis followed by immunoblotting and N-terminal protein microsequencing were used to characterize and identify the IgE-reactive proteins of Hevea latex that are the main cause of the latex type I allergy affecting especially health care workers and spina bifida children. This approach generated a comprehensive latex allergen database, which facilitated the integration of most of the latex allergen data presented in the literature. The major latex allergens Hev b 1, Hev b 3, Hev b 6 and Hev b 7 have been localized on our 2-D maps. Moreover, we were able to identify six previously undescribed IgE-binding latex proteins, namely enolase, superoxide dismutase, proteasome subunit C5, malate dehydrogenase, triosephosphate isomerase and endochitinase. The generated latex 2-D maps will provide valuable information to develop strategies for the isolation of the novel IgE binding proteins in order to study the frequency of sensitization among both risk groups. Detailed knowledge of all proteins involved in latex allergy will allow better diagnosis of latex allergy and to monitor the success of prevention strategies that are needed to reduce the high prevalence of latex allergy among both risk groups.

Allergens↗

PubMed1997

Transcripts at the mating type locus of Cochliobolus heterostrophus.

The single mating type locus (MAT) of the heterothallic ascomycete Cochliobolus heterostrophus is composed of a pair of unlike sequences called idiomorphs, each of which encodes one MAT-specific gene (MAT-1 and MAT-2). MAT transcripts were observed in blots of poly(A)+ RNA isolated from cultures grown in minimal medium, but were not detectable after growth of the fungus in complete medium, suggesting that transcription of MAT is tightly regulated. The idiomorphs (MAT-1 = 1297-bp, MAT-2 = 1171-bp) encode transcripts of 2.2 kb (MAT-1) and 2.1 kb (MAT-2), which start 5' and end 3' of the idiomorph within sequences common to both mating types. Analyses of MAT-1 and MAT-2 cDNAs revealed obligatory splicing of one intron (55-bp in MAT-1, 52-bp in MAT-2) within each MAT-specific ORF and optional splicing of two introns (63 and 79-bp) in the long (approximately 0.55 kb) 5' untranslated leader sequences; the 3' untranslated region is 0.46 kb long. Transcription start sites were found 5' of, and within, the 79-bp intron. Optional splicing of the upstream introns and at least two transcription start sites result in three types of transcript: Type I with both 5' introns spliced, Type II with only the 63-bp intron spliced, and Type III with neither 5' intron spliced. The three transcript types are distinguished by various combinations of four short ORFs encoded by the corresponding genomic DNA, in the leader sequences of the MAT mRNAs. The transcript structure suggests several mechanisms by which expression of the MAT genes might be regulated at the level of translation during sexual development.

Amino Acid Sequence↗