Page 11 - Molecular Plant Breeding

Molecular Plant Breeding 2012, Vol.3, No.3, 26 -36
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710 sequences analyzed, there were several genes
related to the anthocyanin metabolism, and 32 ESTs
in total were directly correlated with anthocyanidin
synthesis, representing 3.3% of the total EST sequences.
The structural genes involved with the process of
anthocyanin synthesis included 4-coumarate-CoA ligase,
chalcone synthase, chalcone isomerase, flavonoid 3',5'-
hydroxylase, anthocyanidin 3-O-glucosyltransferase,
glutathione S-transferase and so on. Other structural
genes were not detected, which probably was due to
the low abundance. The related genes of anthocyanin
synthesis pathway, as a branch of flavonoid synthesis
pathway, were highly expressed at the veraison (Table 4).
The regulatory genes were first studied in model
plants, such as maize, petunia and snapdragon, which
were characterized in Arabidopsis (Davies and
Schwinn, 2003; Broun, 2005). The main types of
transcription factors that activate the structural genes
and initiate the anthocyanin synthesis pathway
effectively include MYB, MYC (bHLH), WD40,
WKRY, Zinc finger and Homeodomain. In this
pathway, the myb-related transcription factor was
detected, and 12 clones representing 12 ESTs were
relevant to zinc finger. The current mechanism of
regulation accepted is that MYB and MYC interact as
co-activators of the biosynthetic genes, and the WD40
repeat-proteins somehow assist in this process (Davies
and Schwinn, 2003; Broun, 2005). And the tissue
specificity of anthocyanin synthesis depends on this
interaction. Furthermore, the control of the flavonoid
pathway in different plant species is affected by the
promoter regions of the anthocyanin structural genes,
as well as the expression profiles and properties of
the regulatory genes (Boss and Davies, 2009).
In wine grapes, acidity not only impacts the berry
quality, but is also an important factor in deciding the
harvest-date. And the sourness plays an important role
in further processing of berries. Malate as the only
high-proportion organic acid with active metabolism
during ripening, is a must for the balance of acids in
wine grape and favors desirable microorganisms
growth for wine fermentation through preventing
undesirable growth (Kunkee, 1991). Additonally, malate
concentrationaffects secondary processes and thus the
final characteristics of berries (grapes). There are two
pathways of malate synthesis in fruit. The metabolism
of sugars translocated to the berry enables synthesis of
malate in the grape before veraison. Another means of
malate synthesis in the berry is photosynthesis. After
the veraison, malate starts to catabolize through
various alleys, and it is likely a vital resource of
carbon for certain pathways (Sweetman et al., 2009).
Enzymes which are thought to be responsible for
potential metabolic pathways involving malate in fruit
cells were detected. These enzymesinclude alcohol
dehydrogenase (ADH), isocitrate dehydrogenase (IDH),
lactate dehydrogenase (LDH), pyruvate kinase (PK).
ADH plays a central role in stress-response and could
be a fruit-ripening related marker on grapevine. The
up-regulation of some ADH genes for fruit-ripening
implies that ethanol fermentation is a normal
development response in grapes (Sarni-Manchado et
al., 1997; Sweetman et al., 2009; Terrier et al., 2005).
And Tesniere et al (2009) found that over-expression
or down-regulation of VvADH resulted in unexpected
responses at the primary and secondary metabolism
levels in leaves and berries.
Table 4 BLAST matched correlative genes of biosynthetic pathway of anthocyanin in the GenBank
Functional annotation EST numbers Functional annotation EST numbers
Chalcone isomerase 4 Cytochrome C 1
Flavonoid 3',5'-hydroxylase 5 Cytochrome B6 -f complex 1 1
Glutathione S-transferase 8 Cytochrome B-c1 complex subunit 2
4- coumarate-CoA ligase 1 Ubiquinol -cytochrome C reductase 1
Anthocyanidin
3- O-glucosyltransferase
1 Cytochrome C oxidase subunit 6B 1
Chalcone synthase 1 Cytochrome C oxidase subunit 2 1
Cytochrome B5 4 Cytochrome C oxidase subunit 2
Cytochrome P450 89A2 1