Page 6 - Genomics and Applied Biology

Genomics and Applied Biology, 2011, Vol.2 No.2
http://gab.sophiapublisher.com
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recognize and resist many invading pathogens by
inducing a set of defense responses. Ratcliff et al
(1999) revealed that the resistant responses, such as
hypersensitive cell death, systemic acquired resistance,
or posttran- scriptional gene silencing (PTGS), can
prevent virus infection.
1.2 The up- and down- regulated genes
Three down-regulated and four up-regulated genes
were obtained when the three tomato cultivars were
examined using two different arbitrary primers, which
scan all the mRNA in the examined samples. The
Disappearance of bands in the inoculated cultivars
which already appeared in the control is considered as
down-regulated gene. Three down-regulated genes
were observed in all samples except in the control
tomato (genetic pool from the three cultivars) and the
sensitive cultivar TY20. The molecular size of these
genes were measured as 9 kb, 8 kb, and 150 bp, respectively.
Escaler et al (2000) reported the viral infection-
induced down regulation of host gene expre- ssion. In
our study, we observed four upregulated genes with
different molecular sizes: 500 bp, 400 bp, 350 bp and
250 bp, respectively. The upregulated genes were
demonstrated in cultivars TY70/70 (200 bp at 1st and
2 nd weeks) but it was 500 bp in TY70/84 (at 2nd week).
DNA sequence and sequence analysis revealed that
the 400 bp upregulated genes of cultivars TY70/84
and TY70/70 were cytochrome oxidase (Figure 2). A
band with molecular size ~350 bp was observed in all
the examined tomato cultivars on the first day; the
expression increased in the two resistant culivars, but
it was considerably low (low band intensity) in the
control tomato plants and the sucsceptible cultivar
TY20. This band was excised from the sensitive
cultivar TY20 (low band expression) and from the
resistant cultivar TY70/84 (high band intensity),
which was then sequenced. The sequence analysis of
the two bands showed that they were cytochrome
oxidase genes. The two sequences showed they were
very close to each other but the cytochrome of the
sensitive TY20 has deletion in two amino acids in
addition to substitution of two amino acids, one at
position 74 (M~I) and the other at the position 116
(L~F) (Figure 3). Belava et al (2010) reported that
resistance of plants to pathogens is determined by
complicated interdependent systems, which are genetically
Figure 2 Differential display technique using two different primers on three tomato cultivars (TY20, TY70/84 and TY70/70)
inoculated with spell out TBSV
Note: The samples were taken on three intervals, 1 day, one week and after two weeks post inoculation; Cy: Cytochrom oxidase gene;
Aly: ALY-family genes