-
[show abstract]
[hide abstract]
ABSTRACT: Genomic instability is related to a wide-range of human diseases. Here, we show that mitochondrial iron-sulfur cluster biosynthesis is important for the maintenance of nuclear genome stability in Saccharomyces cerevisiae. Cells lacking the mitochondrial chaperone Zim17 (Tim15/Hep1), a component of the iron-sulfur biosynthesis machinery, have limited respiration activity, mimic the metabolic response to iron starvation and suffer a dramatic increase in nuclear genome recombination. Increased oxidative damage or deficient DNA repair do not account for the observed genomic hyperrecombination. Impaired cell-cycle progression and genetic interactions of ZIM17 with components of the RFC-like complex involved in mitotic checkpoints indicate that replicative stress causes hyperrecombination in zim17Δ mutants. Furthermore, nuclear accumulation of pre-ribosomal particles in zim17Δ mutants reinforces the importance of iron-sulfur clusters in normal ribosome biosynthesis. We propose that compromised ribosome biosynthesis and cell-cycle progression are interconnected, together contributing to replicative stress and nuclear genome instability in zim17Δ mutants.
Nucleic Acids Research 04/2011; 39(14):6002-15. · 8.03 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: This study investigates whether, and how, polyamines (PAs) are involved in mature fruit abscission of olive (Olea europaea L.). Physiological abscission was studied in relation to the activation of the abscission zone (AZ), located between fruit and peduncle, from two olive cultivars where the breakstrength profiles and the scanning electron micrographs illustrated differences in the abscission program, under natural conditions, of mature fruit. The localization and activities of diamine oxidase (DAO), polyamine oxidase (PAO) and PA biosynthetic enzymes, together with PA content were investigated in the fruit AZ during development and abscission. The activities of arginine decarboxylase and S-adenosyl-l-methionine decarboxylase in the fruit AZ were significantly increased and decreased, respectively, by mature fruit abscission, in good agreement with the rise in free putrescine (Put), and content in uncommon PAs there, such as homospermidine and cadaverine, while no significant differences in free spermidine (Spd) and spermine (Spm) contents were detected. By contrast, an abscission-induced decrease was noted in the contents of insoluble conjugated Put, Spd and Spm. The maximum activity of PAO coincided with the maximum content of Spd and Spm, and it was localized mainly in parenchyma cells of pith, while DAO was present mainly in parenchyma cells of pith and cortex as well as at the base of the vascular tissue. These results suggest a clear correlation between the PA distribution and mature fruit abscission. The regulation of PA metabolism is discussed in relation to mature fruit abscission.
Journal of plant physiology 11/2010; 167(17):1432-41. · 2.50 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Polyamines (PAs) are required for cell growth and cell division in eukaryotic and prokaryotic organisms. The present study is aimed at understanding the developmental regulation of PA biosynthesis and catabolism during flower opening and early fruit development in relation to fruit size and shape. Two full-length cDNA clones coding for S-adenosyl methionine decarboxylase (SAMDC) and spermidine synthase (SPDS) homologs, key steps in the PA biosynthesis pathway, in the stone-fruit of olive (Olea europaea L.) were identified and the spatial and temporal organization of these genes were described. In olive flowers, OeSAMDC gene transcripts were highly expressed in ovary wall, placenta and ovules, while OeSPDS transcript was confined to the ovules of ovary at anthesis stage. A correlation was detected between the SAMDC enzyme activity/accumulation transcript and spermidine (Spd) and spermine (Spm) levels during flower opening, implying that the synthesis of decarboxylated SAM might be a rate-limiting step in Spd and Spm biosynthesis. OeSAMDC and OeSPDS transcripts were co-expressed in fruit mesocarp and exocarp at all developmental stages analyzed as well as in nucellus, integuments and inner epidermis tissues of fertilized ovules. In contrast, the OeSAMDC and OeSPDS genes had different expression patterns during early fruit development. The results provide novel data about localization of PA biosynthesis gene transcripts, indicating that transcript levels of PA biosynthesis genes are all highly regulated in a developmental and tissue-specific manner. The differences between the two olive cultivars in the fruit size in relation to the differences in the accumulation patterns of PAs are discussed.
Planta 08/2010; 232(3):629-47. · 3.00 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Treatment with cyclohexylamine, an inhibitor of spermidine synthase, accelerated radicle emergence in chick-pea (Cicer arietinum L. cv. Castellana) seeds. Stimulation in the growth of embryonic axis was correlated with: (a) a rise in putrescine (Put) and cadaverine (Cad); (b) a decrease in spermidine (Spd) and spermine (Spm), and (c) a concomitant acceleration of the transformation from S-adenosylmethionine (SAM) into ethylene with increases in the levels of l-aminocyclopropane-l-carboxylic acid (ACC), l-(malonylamino)cyclopropane-l-carboxylic acid (mACC) and ethylene and ACC synthase and ethylene-forming enzyme activities. Cyclohexylamine also stimulated the mitotic index in both apical and subapical zones of the radicle and the apical zone of the plumule. The sectional distribution of the ethylene pathway and polyamine content was studied in embryonic axes of seeds germinated for 65 h. Each axis was divided into 5 sections: radicle meristem, elongation zone, differentiation zone, hypocotyl and plumule. In the presence of cyclohexylamine, ACC synthase and ACC were strongly stimulated in both the differentiation and hypocotyl zones, whereas the mACC was stimulated in all sections of the embryonic axis. With respect to ethylene-forming enzyme activity and ethylene production, the hypocotyl and the zones of elongation and differentiation were affected most by cyclohexylamine. Cyclohexylamine also induced an accumulation of free Put and Spm in the differentiation, hypocotyl and radicle zones, whereas Put and Spm bound to small substances increased most in the hypocotyl and plumule. The Spd bound to small substances decreased in all sections in the presence of cyclohexylamine. With respect to polyamines bound to macromolecules, cyclohexylamine stimulated only the accumulation of Put since Spd and Spm were strongly inhibited in all sections.
Physiologia Plantarum 04/2006; 91(1):9 - 16. · 3.11 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The flower opening of damson plum (Prunus insititia L.) was accompanied by an increase in the content of free-polyamines (PA) in the sepals, petals and sex organs, the ovary being most active in accumulating spermine (Spm). The fertilization process and senescence brought on a decline in ovarian Spm, but stimulated putrescine (Put) and spermidine (Spd) content in the sepals. The endocarp of this climacteric fruit produced only ethylene at the end of the S1 phase and throughout S2, in which there was a great richness in ACC and MACC. The greatest amounts of ACC and MACC were observed in the ripening mesocarp and epicarp. The contribution of the endocarp and epicarp to the total ACC in the developing fruit was very similar. During flowering and S1 and S2 phases, Spd was the most abundant PA; in contrast, during S3 and S4 Put was most abundant. The mesocarp contributed the most to the total content in PA throughout the fruit development. The control of SAM distribution towards ethylene and/or PA appears to differ during the development of the endocarp, as the only peak of free-Put (detected in S2) coincided with the highest ACC accumulation and ethylene production. On the contrary, in S3 it is probable that SAM was transformed preferentially into PA, given that free-Spd and Spm, hardly detectable in S1 and S2, peaked in this phase in which there was no gas production.
Journal of Plant Physiology 02/2006; 163(1):86-97. · 2.79 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Higher plants have several strategies to perpetuate themselves under adequate ecophysiological conditions. The production of heterogeneous seeds is one such strategy. That is, to ensure the survival of the next generation, an individual plant might produce seeds that are heterogeneous with respect to the extent of dormancy, dispersion and persistence within the seed bank. Heterogeneity can affect not only certain physiological and molecular properties related to seed germination, but also such characteristics as colour, size and shape, parameters commonly used to differentiate morphs within a heterogeneous seed population. In heterogeneous seeds, the above features determine seed behaviour and alter their mechanism of germination. In this work, emphasis is placed on the existence of seed mutants having major alterations in characteristics of the testa and hormonal response. These mutants constitute a valuable tool for elucidating the mechanism of dormancy, germination and perpetuation of seeds. Finally, ontogeny and heterogeneity are reviewed, providing the first data related to the possible hormonal control of heterogeneity in seeds. These results raise the hypothesis that one of the factors triggering differences in germination among heterogeneous seeds may be an alteration in the signalling and action mechanism of ethylene and abscisic acid (ABA).
Seed Science Research 05/2005; 15(02):63 - 76. · 1.06 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: PAF is a five-subunit protein complex composed of Paf1, Cdc73, Leo1, Rtf1 and Ctr9, which was purified from yeast in association with RNA polymerase II and which is believed to function in transcription elongation. However, no direct proof exists for this yet. To assay whether PAF is required in elongation, we determined the in vitro transcription-elongation efficiencies of mutant cell extracts using a DNA template containing two G-less cassettes. paf1Delta or cdc73Delta cell extracts showed reduced transcription-elongation efficiencies (16-18% of the wild-type levels), whereas leo1Delta and rtf1Delta showed wild-type levels. In vivo transcription efficiency was diminished in the four mutants analysed, as determined by their abilities to transcribe lacZ. Our work provides molecular evidence that PAF has a positive role in transcription elongation and is composed of at least two functionally different types of subunits (Paf1-Cdc73 and Leo1-Rtf1).
EMBO Reports 02/2004; 5(1):47-53. · 7.36 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: THP1 is a conserved eukaryotic gene whose null mutations confer, in yeast, transcription and genetic instability phenotypes and RNA export defects similar to those of the THO/TREX complex null mutations. In a search for multicopy suppressors of the transcription defect of thp1Delta cells, we identified the poly(A)+ RNA-binding heterogeneous nuclear ribonucleoprotein Nab2p. Multicopy NAB2 also suppressed the RNA export defect of thp1Delta cells. This result suggests a functional relationship between Thp1p and Nab2p. Consistently, the leaky mutation nab2-1 conferred a transcription defect and hyper-recombination phenotype similar to those of thp1Delta, although to a minor degree. Reciprocally, a purified His6-tagged Thp1p fusion bound RNA in vitro. In a different approach, we show by Western analyses that a highly purified Thp1p-Sac3p complex does not contain components of THO/TREX and that sac3Delta confers a transcription defect and hyper-recombination phenotype identical to those of thp1Delta. mRNA degradation was not affected in thp1Delta mutants, implying that their expression defects are not due to mRNA decay. This indicates that Thp1p-Sac3p is a structural and functional unit. Altogether, our results suggest that Thp1p-Sac3p and Nab2p are functionally related heterogeneous nuclear ribonucleoproteins that define a further link between mRNA metabolism and transcription.
Journal of Biological Chemistry 07/2003; 278(26):24225-32. · 4.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: RNA biogenesis is a tightly-regulated process. The levels and timing of expression of a gene depends on its particular function. However, gene expression levels may also depend on structural features. Here we describe the analysis of gene expression of 4977 ORFs using DNA microarrays covering the whole genome of three different S. cerevisiae strains, wild-type and tho2 and thp1 mutants with a general effect on mRNA biogenesis. We show that transcripts from G+C-rich ORFs accumulate at higher concentrations than those from G+C-poor ones, in different ORF-length categories in all strains tested. In addition, we found a negative correlation between ORF length and G+C content. Our results indicate that length and G+C content of a gene have a clear effect on its levels of expression. We discuss the biological relevance of these results, as well as different ways that these structural features could modulate mRNA biogenesis.
Yeast 07/2003; 20(8):703-11. · 1.89 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Prior to the embryogenic study of Brassica rapa (turnip tops), the PA (polyamine) changes during flower development were determined. Whereas the flower was closed, no notable changes were found. However, pollination strongly stimulated the synthesis of the F (free) and ASC (acid soluble conjugated) forms, the pistil and not the petals being the main responsible. During embryogenesis, major alterations appeared in the synthesis of free and conjugated PA and ABA. Seeds, and not the silique wall, contributed most to the total content of the different F-PA (free polyamines) in the silique, this contribution involving all the PA studied. During seed desiccation, F-Put remained almost undetectable whereas F-Spd and F-Spm were very high. This is also applicable to ASC-Spd and ASC-Spm, this not being noted in the silique wall. During the first 5 stages of silique embryogenesis, the wall had higher levels of AIC-PA (acid insoluble conjugated polyamines) than in the seeds, primarily due to AIC-Spd and AIC-Spm. By contrast, during the middle and final phases AIC-PA was found more in the seeds than in the silique wall. The free and conjugated ABA showed the presence of 3 and 2 peaks in the seeds and the silique wall, respectively. The first corresponded to the onset of development, the second appeared when the highest moisture content was reached, and the third coincided with the triggering of carotenoid synthesis when the seed and the silique wall had lost more than 70–75% of their moisture. Finally, it is shown that the dry seeds of turnip tops were highly heterogeneous, not only in their germinative capacity, but also in the levels of free and conjugated ABA, which increased inversely to the germinative capacity.
Physiologia Plantarum 03/2003; 117(2):279 - 288. · 3.11 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The effect of short-chain saturated fatty acids (C5–C10) on the biosynthesis of ethylene in embryonic axes of chick-pea (Cicer arietinum L.) seeds was investigated. The emergence of radicle and fresh weight of embryonic axes diminished with increasing number of carbons. The inhibition of germination caused by lower concentrations (1 mM) of fatty acids (C5–C10) was partially reversed by exogenous 1-aminocyclopropane-1-carboxylic acid (ACC), whereas exogenous ethylene was able to overcome the inhibitory effect provoked by all concentrations (1–5 mM) of applied fatty acids (C5–C10). Ethylene production rates, and enzyme activities of ACC synthase and ACC oxidase decreased concomitantly with the molecular mass and increasing concentration of fatty acids. The inhibitory effect of these acids on ethylene production seems to result not only from a decreased ACC synthesis, but also from an enhancement of 1-malonylamino)cyclopropane-1-carboxylic acid (MACC) synthesis.
Physiologia Plantarum 11/1994; 92(4):629 - 635. · 3.11 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The effect of supraoptimal temperatures (30 degrees C, 35 degrees C) on germination and ethylene production of Cicer arietinum (chick-pea) seeds was measured. Compared with a 25 degrees C control, these temperatures inhibited both germination and ethylene production. The effect of supraoptimal temperatures could be alleviated by treating the seeds with ethylene. It was concluded that one effect of high temperature on germination was due to its negative effect on ethylene production. This inhibitory effect of high temperature was due to increased conjugation of 1-aminocyclopropane-1-carboxylic acid to 1-(malonylamino)cyclopropane-1-carboxylic acid and to an inhibition of ethylene-forming enzyme activity.
Plant physiology 10/1991; 97(1):122-7. · 6.53 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The alterations in the ethylene biosynthetic pathway provoked by cyclohexylamine (CHA) and/or methylglyoxal-bis(guanylhydrazone) (MGBG), inhibitors of the polyamine synthesis, have been studied in thermoinhibited seeds (delayed germination by supraoptimal temperatures) of the chick-pea (Cicer arietinum). CHA and/or MGBG stimulated ethylene synthesis both at 25°C (control) and at 30°C (temperature at which thermoinhibition is induced, and reversed by both inhibitors). Moreover, both inhibitors caused: (1) an increase in ACC-synthase (EC 4.4.1.14) and free ACC; (2) a stimulation of in vivo ACC-oxidase; and (3) a stimulation of (malonyl)-1-aminocyclopropane-1-carboxylic acid synthesis at 25°C (since the supraoptimal temperatures had no effect). Compared with the control, both supraoptimal temperatures lead to a decrease the AdoMet-decarboxylase (AdoMetDC) (EC 4.1.1.50) activity. This was not affected by CHA. However, MGBG induced an increase of this activity at 25°C and at 30°C, which diminished strongly up to 35°C. The fact that the inhibition of spermidine and spermine synthesis by CHA and/or MGBG provoked an induction of the enzyme of ethylene biosynthesis and a concomitant increase in ethylene production and a reversion of thermoinhibition in chick-pea seeds suggests that the ethylene and polyamine pathways compete during germination, placing polyamines in the possible role of an endogenous germination regulator possibly by modulating ethylene biosynthesis.
Plant Science.
-
[show abstract]
[hide abstract]
ABSTRACT: Cyclohexylamine and methylglioxalbis(guanylhydrazone), inhibitors of polyamine synthesis, when added to the germination medium of Cicer arietinum L. seeds, increase the germination percentage and ethylene level in both control (25°C) and thermo-inhibited seeds (30°C). This stimulation is inhibited at higher temperatures (35°C), ethylene is not produced and putrescine and spermine are accumulated, both in free and bound forms. The inhibition of the biosynthetic pathway or action of ethylene by norbornadiene and CoCl2 not only causes an important accumulation of free and bound polyamines, but also prevents germination. In the seed response to aminoethoxyvinylglycine, both biosynthetic pathways are altered. The physiological implications of the distribution of S-adenosylmethionine is discussed in relation to the importance of ethylene synthesis in Cicer arietinum seed germination.
Plant Science.
