Biomedical subjects

M Tadege

Publications and source records attributed to M Tadege.

4 recordsLinked to original sources

PubMed2001

Control of flowering time by FLC orthologues in Brassica napus.

FLOWERING LOCUS C (FLC) in Arabidopsis encodes a dosage dependent repressor of flowering. We isolated five FLC-related sequences from Brassica napus (BnFLC1-5). Expression of each of the five sequences in Arabidopsis delayed flowering significantly, with the delay in flowering time ranging from 3 weeks to more than 7 months, relative to the flowering time of 3 weeks in untransformed Ler. In the reciprocal experiment, expression of Arabidopsis FLC (AtFLC) in an early flowering B. napus cultivar delayed flowering by 2-6 weeks, confirming the requirement of this gene for floral repression. In B. napus, we show that late flowering and responsiveness to vernalization correlate with the level of BnFLC mRNA expression. The different BnFLC genes show differential expression in leaves, stems and shoot tips, but expression is not detectable in roots. Vernalization dramatically reduces the level of BnFLC transcript and restores early flowering in the winter cultivar Colombus. We conclude that BnFLC genes confer winter requirement in B. napus and account for the major vernalization-responsive flowering time differences in the different cultivars of B. napus in a manner analogous to that of AtFLC in Arabidopsis ecotypes.

Amino Acid Sequence↗

PubMed2000

The control of flowering by vernalization.

The process by which vernalization, the exposure of a germinating seed or a juvenile plant to a prolonged period of low temperature, promotes flowering in the adult plant has remained a mystery for many years. The recent isolation of one of the key genes involved in vernalization, FLOWERING LOCUS C, has now provided an insight into the molecular mechanism involved, including the role of DNA methylation.

Arabidopsis↗

PubMed1999

Ethanolic fermentation: new functions for an old pathway.

Ethanolic fermentation is an ancient metabolic pathway. In plants, it is a major route of ATP production under anaerobic conditions. In addition, recent developments suggest that the pathway has important functions in the presence of oxygen. Both of the enzymes required for the production of acetaldehyde and ethanol, pyruvate decarboxylase and alcohol dehydrogenase, are highly abundant in pollen, resulting in fermentation in fully oxygenated cells. Acetaldehyde toxicity is an inevitable side effect of aerobic fermentation. Could acetaldehyde be the elusive pollen factor that contributes to male sterility in cmsT maize? The versatility of this ancient pathway is also illustrated by the induction of aerobic fermentation by environmental stress and activation of a defense response by overexpression of pyruvate decarboxylase.

Journal Article↗

PubMed1997

Aerobic fermentation during tobacco pollen development.

In vegetative organs of plants, the metabolic switch from respiration to fermentation is dictated by oxygen availability. The two genes dedicated to ethanolic fermentation, pyruvate decarboxylase and alcohol dehydrogenase, are induced by oxygen deprivation and the gene products are active under oxygen stress. In pollen, these two genes are expressed in a stage-specific manner and transcripts accumulate to high levels, irrespective of oxygen availability. We have examined the expression pattern of pyruvate decarboxylase and alcohol dehydrogenase at the protein level in developing pollen and show that the active proteins are localized to the gametophytic tissue and begin to accumulate at microspore mitosis. A flux through the ethanolic fermentation pathway could already be detected very early in pollen development, occurring in all stages from premeiotic buds to mature pollen. This flux was primarily controlled not by oxygen availability, but rather by sugar supply. At a high rate of sugar metabolism, respiration and fermentation took place concurrently in developing and germinating pollen. We propose that aerobic fermentation provides a shunt from pyruvate to acetyl-CoA to accommodate the increased demand for energy and biosynthetic intermediates during pollen development and germination. A possible undesirable side-effect is the potential accumulation of toxic acetaldehyde. Our results support a model for cms-T-type male sterility in maize, in which degeneration of the tapetum is caused by the toxic effects of acetaldehyde on mitochondria weakened by the presence of the URF13 protein.

Aerobiosis↗