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IN BRIEF
Unpuréeing the Tomato: Layers of Information Revealed by
Microdissection and High-Throughput Transcriptome Sequencing
Understanding the development of a complex structure such as a fruit provides both
an interesting developmental model and an
important task for agriculture, holding the
potential of improving both product quality
and human nutrition (Klee, 2010). For this
task, the tomato (Solanum lycopersicum)
fruit has proven a tractable model system,
with complex metabolism and accessible
genetics and genomics (Carrari and Fernie,
2006). For fruit quality, characterizing the
complex mixture of sugars, acids, and
volatiles that contribute to tomato flavor
and the alterations of cell wall structure that
contribute to tomato texture will be essential for improving the quality of tomatoes
that have been bred for yield and stability
during postharvest handling. For nutrition,
characterizing the important phytonutrients, such as flavonols, vitamin A precursors, and antioxidants, will be essential
to improve human health in both over- and
undernourished populations.
In addition to its tremendous metabolic
complexity, there is also a great spatial
complexity to a developing tomato fruit.
Because most previous studies have characterized tomato fruit development using
homogenized pericarp tissues, this spatial
complexity has been lost. To remedy this,
Matas et al. (pages nnn) combined laser
capture microdissection of specific fruit
cell types with high-throughput pyrosequencing to examine the transcriptomes of key
tomato tissues. They characterized the outer
and inner epidermis, the collenchyma, the
parenchyma, and the vascular tissues of the
developing tomato pericarp in tomato fruits at
the maximal expansion stage (see figure).
Although this preripening stage does not
show the complexities associated with ripening, this proof-of-concept study does allow
examination of key factors in tomato development.
After optimizing the fixation and sectioning methods to get the best recovery of
sequences from each tissue, the authors
examined the distribution of over 20,000
unigenes by both hierarchical clustering
and pairwise comparisons. They found that
821 transcription factors showed different
expression patterns in the different tissues,
demonstrating that this method can help
reveal the regulation of tissue differentiation. They also examined the implementation of tissue differentiation by profiling
genes with functions involved in energy
metabolism, cell wall dynamics, and cuticle
formation. Interestingly, in the examination
of the tissue specificity of genes involved in
cuticle formation, they found that the inner
epidermis of the pericarp also develops
a cuticle. Indeed, they verified the properties of this inner cuticle by characterizing its
structure and lipid composition. Thus, this
method has proven useful for elucidating
the spatial complexities of tomato fruit
differentiation as well as for the examination of cell types and for gene discovery.
Jennifer Mach
Science Editor
[email protected]
REFERENCES
Laser capture microdissection of tomato fruit. Tomato fruit in cross section (A). Labels indicate pericarp
(p), empty locule (l), columella (c), seed (s), outer epidermis (oep), and inner epidermis (iep). Cryosection of
the tomato fruit pericarp before microdissection (B). Labels indicate outer epidermis (oep), collenchyma
(col), vascular bundle (vas), parenchyma (par), and inner epidermis (iep) of the pericarp. Cryosection after
microdissection of the vascular bundle; dissected area is indicated by arrows (C). Bars = 5 mm in (A) and
100 mm in (B) and (C). (Reprinted from Figures 1A, 1D, and 1G of Matas et al. [2011].)
Carrari, F., and Fernie, A.R. (2006). Metabolic
regulation underlying tomato fruit development. J. Exp. Bot. 57: 1883–1897.
Klee, H.J. (2010). Improving the flavor of fresh
fruits: Genomics, biochemistry, and biotechnology. New Phytol. 187: 44–56.
Matas, A.J., et al. (2011). Tissue- and cell-type
specific transcriptome profiling of expanding
tomato fruit provides insights into metabolic
and regulatory specialization and cuticle formation. Plant Cell 23: nnn.
www.plantcell.org/cgi/doi/10.1105/tpc.111.231111
The Plant Cell Preview, www.aspb.org ã 2011 American Society of Plant Biologists. All rights reserved.
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Unpuréeing the Tomato: Layers of Information Revealed by Microdissection and
High-Throughput Transcriptome Sequencing
Jennifer Mach
Plant Cell; originally published online November 9, 2011;
DOI 10.1105/tpc.111.231111
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