Abstract:
Somatic embryos of Persian walnut were transformed
with two strains of
Agrobacterium tumefaciens i.e.
LBA4404 and C58, and two plasmids, namely, pBI121
with
nptII
and
gus
genes for improving the transformation protocol, a
nd p6u-ubi-FVTI
plasmid containing the
hpt
and
fld
genes. The transformation frequency was 10%. PCR
and RT-PCR analysis proved the presence and express
ion of the genes. The transgenic
and non-transgenic somatic embryos of Persian walnu
t were exposed to four salinity
levels (0, 50, 100, and 200 mM NaCl) and four osmot
ic stress (0, 1.5, 5, and 10% PEG)
levels. After 20 days, the number of survived, seco
ndary and cotyledonary somatic
embryos, as well as fresh and dry weights of embryo
s were evaluated. In addition, the
transgenic and non-transgenic regenerated plantlets
with 3 leaves and 2.5 cm length were
subjected to 200 mM NaCl. In both experiments, the
main effects of
fld
-transformation
and stress treatments on evaluated parameters were
significant. Transgenic somatic
embryos showed no significant differences at 0 and
200 mM NaCl and 0 and 1.5% PEG.
Significant differences of transgenic vs. non-trans
genic somatic embryos were observed at
50 and 100 mM NaCl and 5 and 10% PEG. Non-transgeni
c plantlets on medium
containing 200 mM NaCl showed complete necrosis and
died after 10 days, while
transgenic lines continued growth until 45 days. Ou
r results clearly showed that
expression of
fld
gene increased stress tolerance in
fld
transformant lines of walnut, and
also revealed that expression of this specific cyan
obacterial protein may provide a
powerful tool to improve tolerance to environmental
stresses.
Keywords
: Flavodoxin, Salinity stress tolerance, Walnut tra
nsformation.
