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Nazarian Firouzabadi F Kok-Jacon GA Vincken JP Ji Q Suurs LC Visser RG 《Transgenic research》2007,16(5):645-656
It has been shown previously that mutan can be co-synthesized with starch when a truncated mutansucrase (GtfICAT) is directed
to potato tuber amyloplasts. The mutan seemed to adhere to the isolated starch granules, but it was not incorporated in the
starch granules. In this study, GtfICAT was fused to the N- or C-terminus of a starch-binding domain (SBD). These constructs were introduced into two genetically
different potato backgrounds (cv. Kardal and amf), in order to bring GtfICAT in more intimate contact with growing starch granules, and to facilitate the incorporation of
mutan polymers in starch. Fusion proteins of the appropriate size were evidenced in starch granules, particularly in the amf background. The starches from the various GtfICAT/SBD transformants seemed to contain less mutan than those from transformants
with GtfICAT alone, suggesting that the appended SBD might inhibit the activity of GtfICAT in the engineered fusion proteins.
Scanning electron microscopy showed that expression of SBD-GtfICAT resulted in alterations of granule morphology in both genetic
backgrounds. Surprisingly, the amf starches containing SBD-GtfICAT had a spongeous appearance, i.e., the granule surface contained many small holes and grooves,
suggesting that this fusion protein can interfere with the lateral interactions of amylopectin sidechains. No differences
in physico-chemical properties of the transgenic starches were observed. Our results show that expression of granule-bound
and “soluble” GtfICAT can affect starch biosynthesis differently. 相似文献
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