307 research outputs found
Mechanism of Fruit Ripening - Chapter 16
The fruit ripening process has been viewed over the last decades as being
successively of physiological, biochemical, and molecular nature. Fruit ripening
is accompanied by a number of biochemical events, including changes in color,
sugar, acidity, texture, and aroma volatiles that are crucial for the sensory quality
(Fig. 16.1). At the late stages of ripening, some senescence-related physiological
changes occur that lead to membrane deterioration and cell death. In that regard,
fruit ripening can thus be considered as the first step of a programmed cell death
process. All biochemical and physiological changes that take place during fruit
ripening are driven by the coordinated expression of fruit ripening-related genes.
These genes encode enzymes that participate directly in biochemical and physiological
changes. They also encode regulatory proteins that participate in the signaling
pathways, and in the transcriptional machinery that regulate gene expression
and set in motion the ripening developmental progra
Regulation of tomato fruit ripening
Fruit ripening is a sophisticatedly orchestrated developmental process, unique to plants, that
results in major physiological and metabolic changes, ultimately leading to fruit decay and seed
dispersal. Because of their strong impact on fruit nutritional and sensory qualities, the ripeningassociated
changes have been a matter of sustained investigation aiming at unravelling the
molecular and genetic basis of fruit ripening. Tomato rapidly emerged as the model of choice for
fleshy fruit research and a wealth of genetic resources and genomics tools have been developed,
providing new entries into the regulatory mechanisms involved in the triggering and coordination
of the ripening process. Some of the key components participating in the control of tomato fruit
ripening have been uncovered, but our knowledge of the network of signalling pathways engaged in
this complex developmental process remains fragmentary. This review highlights the main
advances and emphasizes issues still to be addressed using the rapidly developing ‘omics’
approaches
Molecular regulation of seed and fruit set
Seed and fruit set are established during and soon after fertilization and determine seed and fruit number, their final size and, hence, yield potential. These processes are highly sensitive to biotic and abiotic stresses, which often lead to seed and fruit abortion. Here, we review the regulation of assimilate partitioning, including the potential roles of recently identified sucrose efflux transporters in seed and fruit set and examine the similarities of sucrose import and hydrolysis for both pollen and ovary sinks, and similar causes of abortion. We also discuss the molecular origins of parthenocarpy and the central roles of auxins and gibberellins in fruit set. The recently completed strawberry (Fragaria vesca) and tomato (Solanum lycopersicum) genomes have added to the existing crop databases, and new models are starting to be used in fruit and seed set studies
Mechanisms of Fruit Ripening: Retrospect and Prospects
This paper aims at giving an overview of the progress made during the last
decades on the mechanisms of fruit ripening and to present the most recent trends
and prospects for the future. Important steps forward will be presented (respiratory
climacteric, ethylene biosynthesis and action, isolation of genes involved in the
ripening process, biotechnological control of fruit ripening....) by showing how the
judicious exploitation of the data published previously, the strategies, methodologies
and plant material adopted have been crucial for the advancement of knowledge.
Opportunities of co-operation between geneticists and post-harvest physiologists as
well as new possibilities offered by genomics, proteomics and metabolomics for the
understanding of the fruit ripening process and the development of sensory quality
will be developed
Silencing Sl-EBF1 and Sl-EBF2 expression causes constitutive ethylene response phenotype, accelerated plant senescence, and fruit ripening in tomato
The hormone ethylene regulates a wide range of plant developmental processes and EBF (EIN3-binding F-box) proteins were shown to negatively regulate the ethylene signalling pathway via mediating the degradation of EIN3/EIL proteins. The present study reports on the identification of two tomato F-box genes, Sl-EBF1 and Sl-EBF2 from the EBF subfamily. The two genes display contrasting expression patterns in reproductive and vegetative tissues and in response to ethylene and auxin treatment. Sl-EBF1 and Sl-EBF2 genes are actively regulated at crucial stages in the development of the reproductive organs. Their dynamic expression in flowers during bud-to-anthesis and anthesis-to-post-anthesis transitions, and at the onset of fruit ripening, suggests their role in situations where ethylene is required for stimulating flower opening and triggering fruit ripening. VIGS-mediated silencing of a single tomato EBF gene uncovered a compensation mechanism that tends to maintain a threshold level of Sl-EBF expression via enhancing the expression of the second Sl-EBF gene. In line with this compensation, tomato plants silenced for either of the Sl-EBF genes were indistinguishable from control plants, indicating functional redundancy among Sl-EBF genes. By contrast, co-silencing of both Sl-EBFs resulted in ethylene-associated phenotypes. While reports on EBF genes to date have focused on their role in modulating ethylene responses in Arabidopsis, the present study uncovered their role in regulating crucial stages of flower and fruit development in tomato. The data support the hypothesis that protein degradation via the ubiquitin/26S proteasome pathway is a control point of fruit ripening and open new leads for engineering fruit quality
Improved Screening of cDNAs Generated by mRNA Differential Display Enables the Selection of True Positives and the Isolation of Weakly Expressed Messages
The high percentage of false positives generated by differential display (as
high as 85%) has previously limited the potential of the method. This report describes
an efficient methodology that enables false positives to be discarded prior to cloning, via
reverse Northern analysis. This first step of the screening also allows the detection of
putative lowabundance differential clones. Following cloning, a second reverseNorthern
combined with partial DNA sequencing and RT-PCR detection allows isolation of all
differential cDNAs including very lowabundance clones. Use of the sequential screening
procedure described here led to the isolation of novel tomato genes responding to the
plant hormone ethylene while minimising labor and materials input
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
Over-expression of a chimeric gene of the transcriptional co-activator MBF1 fused to the EAR repressor motif causes developmental alteration in Arabidopsis and tomato
Transcriptional co-activators of the Multiprotein Bridging Factor1 (MBF1) type belong to a multigenic family that encode key components of
the machinery controlling gene expression by communicating between transcription factors and the basal transcription machinery. Knocking-down
the expression of one member of the family has proved difficult probably due to functional redundancy. We show here that a fusion of SlER24, an
MBF1 type gene of tomato, to the Ethylene-responsive element-binding associated Amphiphilic Repression (EAR) motif is capable of slowing
down significantly the expression of the GFP protein driven by a synthetic ethylene-responsive GCC-rich promoter in a single cell transient
expression system. A fusion of AtMBF1c of Arabidopsis to EAR, driven by the 35S promoter, caused a reduction of the percentage of seed
germination and dwarfism of the plant. Similar fusion with the SlER24 of tomato in the MicroTom cultivar induced a delay of seed germination and
no obvious effect on plant growth. Besides giving information on the role of the MBF1 genes in plant development, this study demonstrates that the
EAR strategy is efficient not only for regular transcription factors as demonstrated so far, but also in the case of co-activators known to not bind
directly to DNA
Editorial : Ethylene biology and beyond : novel insights in the ethylene pathway and its interactions
- …