35 research outputs found
ACC Synthase Genes Related to Cold-dependent Ripening in Pear Fruit
The differential regulation of ACC synthase genes has been studied in pear
cultivars that either require a long chilling treatment before they are capable of
ripening (‘Passe-Crassane’, PC) or not (‘Old-Home’, OH) and in OH x PC hybrids
having no (A16) or intermediate (A50) cold requirement. Among the seven Pc-ACS
cDNAs isolated, four of them (Pc-ACS1a/b and Pc-ACS2a/b) showed differential
expression in relation with cold requirement. Pc-ACS1a transcripts accumulated
specifically during chilling and ripening of cold-dependent cultivars while Pc-ACS1b
transcripts were detected only during ripening of cold-independent genotypes. Pc-
ACS2a mRNA was expressed specifically in cold-dependent genotypes and
negatively regulated by ethylene while Pc-ACS2b transcripts accumulated only in
cold-independent genotypes and positively regulated by ethylene. Pc-ACS3, 4 and 5
transcripts accumulation was similar in all genotypes, independently of coldrequirements
ER5, a tomato cDNA encoding an ethylene-responsive LEA-like protein: characterization and expression in response to drought, ABA and wounding
We report the isolation by differential display of a novel tomato ethylene-responsive cDNA, designated ER5.
RT-PCR analysis of ER5 expression revealed an early (15 min) and transient induction by ethylene in tomato fruit,
leaves and roots. ER5 mRNA accumulated during 2 h of ethylene treatment and thereafter underwent a dramatic
decline leading to undetectable expression after 5 h of treatment. The full-length cDNA clone of 748 bp was
obtained and DNA sequence analysis showed strong homologies to members of the atypical hydrophobic group of
the LEA protein family. The predicted amino acid sequence shows 67%, 64%, 64%, and 61%sequence identity with
the tomato Lemmi9, soybean D95-4, cotton Lea14-A, and resurrection plant pcC27-45 gene products, respectively.
As with the other members of this group, ER5 encodes a predominantly hydrophobic protein. Prolonged drought
stress stimulates ER5 expression in leaves and roots, while ABA induction of this ethylene-responsive clone is
confined to the leaves. The use of 1-MCP, an inhibitor of ethylene action, indicates that the drought induction of
ER5 is ethylene-mediated in tomato roots. Finally, wounding stimulates ER5 mRNA accumulation in leaves and
roots. Among the Lea gene family this novel clone is the first to display an ethylene-regulated expression
Effects of chilling on the expression of ethylene biosynthetic genes in Passe-Crassane pear (Pyrus communis L.) fruits
Passe-Crassane pears require a 3-month chilling treatment at 0 C to be able to produce ethylene and ripen
autonomously after subsequent rewarming. The chilling treatment strongly stimulated ACC oxidase activity, and
to a lesser extent ACC synthase activity. At the same time, the levels of mRNAs hybridizing to ACC synthase and
ACC oxidase probes increased dramatically. Fruit stored at 18 C immediately after harvest did not exhibit any
of these changes, while fruit that had been previously chilled exhibited a burst of ethylene production associated
with high activity of ACC oxidase and ACC synthase upon rewarming. ACC oxidase mRNA strongly accumulated
in rewarmed fruits, while ACC synthase mRNA level decreased. The chilling-induced accumulation of ACC
synthase and ACC oxidase transcripts was strongly reduced when ethylene action was blocked during chilling with
1-methylcyclopropene (1-MCP). Upon rewarming ACC synthase and ACC oxidase transcripts rapidly disappeared
in 1-MCP-treated fruits. A five-week treatment of non-chilled fruits with the ethylene analog propylene led to
increased expression of ACC oxidase and to ripening. However, ethylene synthesis, ACC synthase activity and
ACC synthasemRNAs remained at very lowlevel. Our data indicate thatACC synthase gene expression is regulated
by ethylene only during, or after chilling treatment, while ACC oxidase gene expression can be induced separately
by either chilling or ethylene
Recent Developments on the Role of Ethylene in the Ripening of Climacteric Fruit
It has long been recognised that ethylene plays a major role in the ripening
process of climacteric fruit. A more thorough analysis, however, has revealed that a
number of biochemical and molecular processes associated with climacteric fruit
ripening are ethylene-independent. One of the crucial steps of the onset of ripening
is the induction of autocatalytic ethylene production. In ethylene-suppressed melons,
ACC synthase activity is induced at the same time as in control melons, indicating
that ACC biosynthesis during the early stages of ripening seems to be a
developmentally-regulated (ethylene-independent) process. The various ripening
events exhibit differential sensitivity to ethylene. For instance, the threshold level for
degreening of the rind is 1ppm, while 2.5 ppm are required to trigger some
components of the softening process. The saturating level of ethylene producing
maximum effects is less than 5 ppm, which is by far lower than the internal ethylene
concentrations found in the fruit at the climacteric peak (over 100 ppm). In many
fruit chilling temperatures hasten ethylene production and ripening and in some late
season pear varieties, exposure to chilling temperatures is even absolutely required
for the attainment of the capacity to synthesize autocatalytic ethylene. This is
correlated with the stimulation of expression of ACC oxidase and of members of the
ACC synthase gene family. Ethylene operates via a perception and transduction
pathway to induce the expression of genes responsible for the biochemical and
physiological changes observed during ripening. However, only a few genes induced
via the ethylene transduction pathway have been described so far. We have used a
differential display method to isolate novel ethylene-reponsive (ER) cDNA clones of
tomato that potentially play a role in propagating the ethylene response and in
regulating fruit ripening. Collectively, these data permit a general scheme of the
molecular mechanisms of fruit ripening to be proposed
Heat-induced and spontaneous expression of Hsp70.1Luciferase transgene copies localized on Xp22 in female bovine cells
<p>Abstract</p> <p>Background</p> <p>Expression of several copies of the heat-inducible <it>Hsp70.1Luciferase </it>(<it>LUC</it>) transgene inserted at a single X chromosome locus of a bull (<it>Bos taurus</it>) was assessed in females after X-chromosome inactivation (XCI). Furthermore, impact of the chromosomal environment on the spontaneous expression of these transgene copies before XCI was studied during early development in embryos obtained after in vitro fertilization (IVF), when the locus was carried by the X chromosome inherited from the bull, and after somatic cell nuclear transfer (SCNT) cloning, when the locus could be carried by the inactive Xi or the active Xa chromosome in a female donor cell, or by the (active) X in a male donor cell.</p> <p>Findings</p> <p>Transgene copies were mapped to bovine Xp22. In XX<sup><it>LUC </it></sup>female fibroblasts, i.e. after random XCI, the proportions of late-replicating inactive and early-replicating active X<sup><it>LUC </it></sup>chromosomes were not biased and the proportion of cells displaying an increase in the level of immunostained luciferase protein after heat-shock induction was similar to that in male fibroblasts. Spontaneous transgene expression occurred at the 8-16-cell stage both in transgenic (female) embryos obtained after IVF and in male and female embryos obtained after SCNT.</p> <p>Conclusions</p> <p>The X<sup><it>LUC </it></sup>chromosome is normally inactivated but at least part of the inactivated X-linked <it>Hsp70.1Luciferase </it>transgene copies remains heat-inducible after random XCI in somatic cells. Before XCI, the profile of the transgenes' spontaneous expression is independent of the epigenetic origin of the X<sup><it>LUC </it></sup>chromosome since it is similar in IVF female, SCNT male and SCNT female embryos.</p
Differential regulation of ACC synthase genes in cold-dependent and -independent ripening in pear fruit
Late pear cultivars such as Passe-Crassane (PC) require a long chilling treatment before they are capable of ripening. Early cultivars such as Old-Home (OH) have no cold prerequisite. The regulation of 1-aminocyclopropane-1-carboxylic acid synthase (ACS) genes was studied in OH, PC and in OH x PC hybrids in order to determine the role of this gene family in the cold requirement. Of the seven Pc-ACS cDNAs isolated, four (Pc-ACSla/b and Pc-ACS2a/b) showed differential expression associated with the cold requirement. Pc-ACS1a transcripts accumulated throughout the cold treatment and, with Pc-ACS2a, during ripening of cold-dependent cultivars. Pc-ACS1b and Pc-ACS2b were detected only during ripening of cold-independent genotypes. Furthermore, Pc-ACS2a transcript accumulation was negatively regulated by ethylene, whereas Pc-ACS2b was positively regulated by the hormone. Pc-ACS3, 4 and 5 transcript accumulation was similar in all genotypes. Genetic analyses of OH, PC, and 22 OH x PC progenies demonstrated that late, cold-dependent cultivars were homozygous for Pc-ACS1a and 2a whereas early, cold-independent cultivars were heterozygous for Pc-ACS1(a/b) and homozygous for Pc-ACS2b. A model is presented in which differences in Pc-ACS alleles and gene expression between cold- and non-cold-requiring pears are critical in determining the ripening behaviour of the cultivars
Isolation and characterization of four ethylene perception elements and their expression during ripening in pears (Pyrus communis L.) with/without cold requirement
Pear (Pyrus communis L.) are climacteric fruit: their ripening is associated with a burst of autocatalytic ethylene production. Some late pear cultivars, such as Passe-Crassane (PC) require a long (80 d) chilling treatment before the fruit will produce autocatalytic ethylene and ripen. As the cold requirement is linked to the capacity to respond to ethylene (or its analogue, propylene), three pear cDNAs homologous to the Arabidopsis ethylene receptor genes At-ETR1, At-ERS1, and At-ETR2, designated Pc-ETR1a (AF386509), Pc-ERS1a (AF386515), and Pc-ETR5 (AF386511), respectively, have been isolated. A pear homologue of the Arabidopsis ethylene signal transduction pathway gene At-CTR1, called Pc-CTR1 (AF386508) has also been isolated. The search of the genomic sequences for Pc-ETR1a and Pc-ERS1a resulted in the isolation of four related genomic clones Pc-DETR1a (AF386525), Pc-DETR1b (AF386520), Pc-DERS1a (AF386517), and Pc-DERS1b (AF386522). Analysis of transcript levels for the four cDNAs in PC and pear fruit genotypes with little or no cold requirement revealed that Pc-ETR1a expression increased during chilling treatment, and Pc-ETR1a, Pc-ERS1a, Pc-ETR5, and Pc-CTR1 expression increased during fruit ripening and after ethylene treatment. Whether the differences in the ethylene response elements studied here are the cause or an effect of the cold requirement in PC fruit is discussed