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In this thesis, we investigated the effect of high temperature
on the activity of soluble starch synthase in sorghum immature
seed endosperm and leaf. The results showed that the enzyme
activity of the soluble starch synthase, in terms of 14C-glucose
incorporation rate, in both organs would be decreased under high
temperature treatment, the decrement was especially significant
in waxy sorghum lines, III wx. Our result also showed that, the
enzyme in leaves was more sensitive to the alternation of
temperature than that in the endosperm. The activity of soluble
starch synthase in leaves of the EMS induced waxy mutant EMS-wx
line went quickly down under temperature over 30℃. This was not
a common phenomenon in tropical crops.In order to clone the cDNA
encoding sorghum soluble starch synthase, we used four primers,
which located on the conserved regions of the open reading frame
of rice soluble starch synthase and sorghum Wx cDNA sequence, to
synthesize homologous probes by PCR. The amplified products were
not the Wx-related product, as confirmed by Southern blot
analysis, and they were used as the probes for cDNA library
screening. The plaques forming unit was not high enough to make
the screening efficient. Suitable condition still need to be
tested. By SDS-PAGE and western blot analysis, we identified a
70kD, recognized by anti-Wx protein antiserum, that was present
both in the non-waxy and waxy sorghum immature endosperm.
Whether the protein can be clarified as a isozyme of sorghum
soluble starch synthase or not need more experimental data to
confirm with.
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