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Deng et al., 2011, Ectopic expression of an
AGAMOUS
homolog
NTAG1
from
Chinese narcissus accelerated earlier flowering and senescence in Arabidopsis, Molecular Plant Breeding Vol.2 No.3 (doi: 10.5376/mpb.2011.02.0003)
17
Figure 2 A: The expression of
NTAG
in Chinese narcissus; B:
The
35S::NTAG1
transgenic plants were verified by PCR using
genomic DNA as templates; C: The
35S::NTAG1
transgenic
plants were verified by RT- PCR; D: The expression
SAG12
gene was enhanced in the
35S::NTAG1
transgenic plants; E:
The MDA content was higher in the
35S::NTAG1
transgenic
plants
however the size of flowers was smaller (Figure 1I).
Three lines of transgenic plants produced transformed
flowers, first-whorl organs were transformed into
carpelloid sepals containing stigmatic papillae
(showed by arrows in Figure 1J) and second whorl
organs absent sometimes, the typical homeotic
conversion of sepals and petals similar to that
observed in
ap2
mutants or
AG
ortholog
overexpressed
transgenic
Arabidopsis
plants
(Mizukami and Ma, 1992; Mizukami and Ma, 1997;
Tzeng et al., 2002).
Because the phenotypes varied with the expression of
the transgenic gene, the expression of
NTAG1
gene
was analyzed in five lines of the homozygous
kanamycin-resistant T
3
generation plants by RT-PCR.
The results showed that
NTAG1
gene were ectopic
expressed in these plants (Figure 2C). Compared with
Wt, the
35S::NTAG1
transgenic plants flowered early
(Figure 1K, left) by producing only six-seven small,
curled rosette leaves (Figure 1K, right, Table 1), loss
of inflorescence indeterminacy. The branch number
and the number of inflorescence buds of the transgenic
plants were increased (Table 1). All transgenic plants
produced terminal flowers (Figure 1K) similar to
those observed in Arabidopsis plants ectopically
expressing the
AG
or
AG
orthologs (Mizukami and
Ma, 1992; Rutledge et al., 1998). However, there was
no obvious homeotic conversion of flower organs in
the transgenic plants. When the epidermal cells of the
flower organs were examined by scanning electron
micrographs, the inner three whorls were
morphologically similar to the Wt organs epidermis
(data not shown). The surface of irregularly shaped
cells in Wt sepals are cuticular thickening, whereas
the surface of irregularly shaped cells along with the
interspersed stomata in Wt carpels are smooth (Tzeng
et al., 2002). A 35S::
NTAG1
flower produced sepals
nearly similar to wild type except that surface cells
containing less cuticular thickenings (Figure 1M, N).
Additionlly,we also investigated, the morphological
features of transgenic plants (Table 1). The height of
35S::
NTAG1
plants was 5.6 cm, which was shorter
than that of Wt (11.5 cm). The leaf was smaller, and
the silique was shorter (the average silique length of
35S::
NTAG1
plants was 7.5 mm versus 10.5 mm of
Wt), and the number of branch per plant increased
significantly (the average branch number of
35S::
NTAG1
plants was 8.1 versus 4.0 of Wt).
1.3 Ectopic expression of
NTAG1
accelerated
senescence in transgenic Arabidopsis plants
Even in the vegetative stage, the leaves produced by
Table 1 Morphological features of wild type and
35S::NTAG1
plants
Plants
Leaf number (pc)
Leaf length (mm)
Plant height (cm)
Branch number (pc)
Silique length (mm)
35S::NTAG1
7.3 ±1.1
8.9 ±1.1
5.6 ±2.1
8.1 ±2.6
7.5 ±1.0
Wt
9.6 ±0. 8
12.9 ±1.0
11.5±3.6
4.0 ±2.6
10.5 ±1.3