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Molecular Plant Breeding 2012, Vol.3, No.3, 26
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Figure 6 Gene ontology cell component classification of
annotated genes
Figure 7 Gene ontology molecular function classification of
annotated genes
Figure 8 Gene ontology biological process classification of
annotated genes
For the purpose of better understanding the overall
mechanisms in the pericarps under investigation, Gene
Ontology (GO) annotations were performed and their
correlated MIPS functional categories assigned 710
unigenes to 9 classes of biological function (Figure 9).
In accordance with the biological roles of products
encoded by genes, the nine classes included energy/
metabolism (14.79%), protein synthesis (7.46%), signal
transduction (2.82%), cell disease/defense (2.54%),
transport (3.67%), photosynthesis (0.70%), transcription
(2.54%), protein activity regulation (1.69%) and cell
structure (1.83%). The most represented functional
classes appeared to be energy/metabolism, which was
followed by the protein synthesis and transport;
Figure 9 Biological functional classification of annotated genes
however, the percentage of independent clones
matching with sequences of putative or hypothetical
protein without any predicted function was 36.34%.
Therefore, dramatic changes at veraison are mainly
attributed to energy/metabolism and protein synthesis.
2 Discussion
The grape berry, as the non-climacteric fruit, shows
characteristic double-sigmoidal growth curve. The
time of harvesting and the sugar/acid balance at the
particular ripening stage affects the final quality of the
resulting wine (Fillion et al., 1999). Therefore it is of
the utmost importance to understand and characterize
the berry ripening process, so as to control the
maturation as much as possible. In this research, the
ESTs analysis based on the cDNA library provided
useful information about genes and functions expressed
in the pericarp at veraison of developing berry.
However, there is also 25.63% of the analyzed
sequences which did not match any sequences in
database after the sequencing analysis. Terrier et al
(2001) found that the proportion of unmatched
sequences was the highest at the veraison. Veraison is
the onset of ripening, so some of these new genes
encoding certain specific proteins could actually play
an important role at the transient period which need
further analysis to address their functions.
The striking changes in the mRNA population and
gene expression occur in grape berries as the fruit
enters into the ripening phase (Davies and Robinson,
2000). There is a range of genes whose transcription
level increases at veraison, such as the genes encoding
anthocyanin synthesis pathway enzymes (Boss et al.,
1996). The anthocyanins, as the secondary metabolites
localized in the skin of the berry, are responsible for
quality factors, such as color and flavor. Among the