crose synthesis
Isolation and Induced Expression of a Fructokinase Gene
Q. P. Qin, Y. Y. Cui, L. L. Zhang, F. F. Lin, and Q. X. Lai
School of Agriculture and Food Science, Zhejiang Agriculture and Forestry University, Lin’an, Hangzhou, 311300 China
The Key Laboratory for Quality Improvement of Agricultural Products of Zhejiang Province, Zhejiang A&F University,
Lin’an, Hangzhou, China;
fax: 08657163741276; email: firstname.lastname@example.org, email@example.com
Received January 29, 2013
—Fructose is essential for plant development as well as for fruit sugar composition and fruit quality.
Fructose is one of the major sugars in the mature loquat (
Lindl.) fruit, which is popular
because of its flavor and availability in early summer. The elucidation of the mechanism of fructose metabo
lism is of great importance for fruit quality improving. Fructose is primarily phosphorylated by fructokinase
(FRK). In order to understand the fructose metabolism in the loquat fruit, a putative loquat FRK fulllength
cDNA designated as
was isolated in this study. The
encoding FRK possesses conserved regions
inherent to plant FRKs. Transient expression of 35S:
GFP fusion protein in onion epidermal cells
was mainly expressed in the cytosol. The realtime RTPCR analysis indicated that
was expressed in all loquat tissues. Monitoring the dynamic changes of
transcripts and FRK
enzymatic activities demonstrated that
expression was at a relative high level during early fruit devel
opmental stages and dropped to the lower level during maturation, similar with the changes in FRK activity,
which was opposite to the fructose levels during fruit development. The results indicated that the high FRK
enzymatic activity was not conducive to fructose accumulation in loquat fruit. The
transcript level in
leaves of loquat seedlings was significantly enhanced after 6 h of treatment with 10 and 100 mM fructose or
glucose, which indicates that
is modulated by fructose and glucose in vivo.
Keywords: Eriobotrya japonica
, fructokinase, glycolysis, sugar metabolism
: DAF—days after flowering; FRK—fructokinase;
RACE—Rapid Amplification of cDNA Ends; SDH—sorbitol
dehydrogenase; S6PDH—sorbitol6phosphate dehydrogenase.