24 research outputs found
On the role of ethylene, auxin and a GOLVEN-like peptide hormone in the regulation of peach ripening
BACKGROUND: In melting flesh peaches, auxin is necessary for system-2 ethylene synthesis and a cross-talk between ethylene and auxin occurs during the ripening process. To elucidate this interaction at the transition from maturation to ripening and the accompanying switch from system-1 to system-2 ethylene biosynthesis, fruits of melting flesh and stony hard genotypes, the latter unable to produce system-2 ethylene because of insufficient amount of auxin at ripening, were treated with auxin, ethylene and with 1-methylcyclopropene (1-MCP), known to block ethylene receptors. The effects of the treatments on the different genotypes were monitored by hormone quantifications and transcription profiling. RESULTS: In melting flesh fruit, 1-MCP responses differed according to the ripening stage. Unexpectedly, 1-MCP induced genes also up-regulated by ripening, ethylene and auxin, as CTG134, similar to GOLVEN (GLV) peptides, and repressed genes also down-regulated by ripening, ethylene and auxin, as CTG85, a calcineurin B-like protein. The nature and transcriptional response of CTG134 led to discover a rise in free auxin in 1-MCP treated fruit. This increase was supported by the induced transcription of CTG475, an IAA-amino acid hydrolase. A melting flesh and a stony hard genotype, differing for their ability to synthetize auxin and ethylene amounts at ripening, were used to study the fine temporal regulation and auxin responsiveness of genes involved in the process. Transcriptional waves showed a tight interdependence between auxin and ethylene actions with the former possibly enhanced by the GLV CTG134. The expression of genes involved in the regulation of ripening, among which are several transcription factors, was similar in the two genotypes or could be rescued by auxin application in the stony hard. Only GLV CTG134 expression could not be rescued by exogenous auxin. CONCLUSIONS: 1-MCP treatment of peach fruit is ineffective in delaying ripening because it stimulates an increase in free auxin. As a consequence, a burst in ethylene production speeding up ripening occurs. Based on a network of gene transcriptional regulations, a model in which appropriate level of CTG134 peptide hormone might be necessary to allow the correct balance between auxin and ethylene for peach ripening to occur is proposed. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12870-016-0730-7) contains supplementary material, which is available to authorized users
Observational Limits on Terrestrial-Sized Inner Planets Around the CM Draconis System Using the Photometric Transit Method with a Matched-Filter Algorithm
A lightcurve of the eclipsing binary CM Draconis has been analyzed for the
presence of transits of planets of size >= 2.5 Earth-radii (Re), with periods
of 60 days or less, and in co-planar orbits around the binary system. About 400
million model lightcurves, representing transits from planets with periods
ranging from 7 to 60 days, have been matched/correlated against these data.
This process we call the "transit detection algorithm" or TDA. The resulting
`transit-statistics' for each planet candidate allow the quantification of
detection probabilities, and of false alarm rates.
Our current lightcurve of CM Dra has a coverage of 1014 hours with 26,043
individual points, at a photometric precision between 0.2% and 0.7%. Planets
significantly larger then 3Re would constitute a `supra-noise' detection, and
for periods of 60 days or less, they would have been detected with a
probability of 90%. `Subnoise' detections of smaller planets are more
constrained. For example, 2.5 Re planets with 10-day periods or less would have
been detected with an 80% probability. The necessity for predicted observations
is illustrated with the nine top planet candidates that emerged from our TDA
analysis. They are the planet candidates with the highest transit-statistics
from the 1994-1998 observing seasons and, for them, transits for the 1999
observing season were predicted. Of the seven candidates that were then
observationally tested in 1999, all were ruled out except one, which needs
further observational confirmation. We conclude that the photometric transit
method is a viable way to search for relatively small, inner extrasolar planets
with moderate-sized telescopes using CCD photometry with a matching-filter
analysis.Comment: text in html format; 2 gif files for equations; 9 gif files for
figure