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Cotton Genomics and Genetics 2012, Vol.3, No.1, 1
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signaling molecules, which can induce the expression
of plant defense genes. Thereby plants acquire
resistance to more pathogens (Wang et al., 2004).
SNC1
(suppressor of npr1
-
1, constitution 1) gene
cloned from
Arabidopsis
plays an important role in
the occurrence of the plant system acquired resistance
(SAR), which was salicylic acid signaling based
negative regulator constitutively expressing high
level of PR gene with broad-spectrum disease
resistance; the
SNC1
gene encodes the NB-LRR
(nucletide-binding-leucine-rich repeats) protein (Li
et al., 2001; Zhang et al., 2003). The NCBI Blast
presents that a very small part sequence of the SNC1
gene is similar with the known cotton genome
sequence, but their functions are different. The
SNC1
gene is not yet to be transformed in the other plant.
In this study we attempted to transform the
SNC1
gene
through
Agrobacterium
-mediated approach using stem
apexes as explant to obtain the transgenic cotton, as
well as to inoculate Fusarium disease strain (
Fusarium
oxysporum
f.sp.
Vasinfectum
) into the transgenic
cotton to confirm whether the transgenic cotton acquire
the resistance to Fusarium wilt.
1 Results and Analysis
1.1 The effects of explant culture time on the shoot
tip growth status
To pick up sterile stem apexes cultured in same day,
one day, two days and three days applied to calculate
the generation rates that were from the explants to the
green seedlings. The statistical results showed that the
generation rate of sterile stem apexes of Zhong35 and
Junmian No.1 cultured in same day were 44.1% and
43.7%, respectively, while cultured in 2 or 3 days the
generation rate were 54.2% to 70.0%, respectively;
whereas the generation rate of sterile stem apexes of
Zhong35 and Junmian No 1 cultured in one day
reached 80.9% and 81.5%, respectively (Table 1).
1.2 The effect of bacterium infection time on the
shoot apex growth status
Using Dissecting needle tip to make traumas on
meristem zone of shoot apexes, bacterium infection
time were set 10 min, 20 min and 30 min. We found
that the generation rate of sterile stem apexes of
Zhong35 and Junmian No.1 infected by 10 min were
56.1% and 62.0%, respectively, while infected by
30 min the explants grew up slowly, the seedlings
were small and dwarf; whereas the generation rate of
sterile stem apexes of Zhong35 and Junmian No.1
infected by 20 min reached 76.7% and 74.6%,
respectively (Table 2).
1.3 The effect of co-culture time on shoot apex
growth status
The co-culture time was set for 1 day, 2 days, 3 days
and 4 days. The results showed that the morphology
of all cultured stem apexes unchanged after 1 day
culture bur the top of shoot apexes became expanding
and thickening; cultured for 3 days and 4 days, apical
length of root grew up from 20 mm to 30 mm in
length, but the middle of the root dehydrated and the
root tips were severe browning, while the bacteria
begin to grow; cultured 2 days shoot tip length grew
up about 10 mm, after inoculated on the screening
medium, the top of stem apexes gradually became
light brown, it was obvious that the restoring time for
their growth was short and young buds were robust,
the regeneration rate of sterile stem apexes of
Zhong35 and Junmian No.1 can reach 66.2% and
71.9% , respectively (Table 3).
Table 1 Effect of explant-cultured time on the growth status of shoot apex
Growth time (d) Variety
Average No. of
transformed plants
Average No. of
survival plants
Transformation
Rate
(%)
0
Zhong35
102
45
44.1
Junmian No.1
87
38
43.7
1
Zhong35
157
127
80.9
Junmian No.1
124
101
81.5
2
Zhong35
130
91
70.0
Junmian No.1
130
87
66.9
3
Zhong35
126
72
57.1
Junmian No.1
131
71
54.2