Starch, the main component of the wheat grain, is the product of a complex biochemical pathway. The sbeⅡa gene plays a key role in controlling the synthesis of starch, in particular, the biosynthesis of amylopectin, ...Starch, the main component of the wheat grain, is the product of a complex biochemical pathway. The sbeⅡa gene plays a key role in controlling the synthesis of starch, in particular, the biosynthesis of amylopectin, in maturing wheat grain. To investigate its regulatory mechanisms and endosperm-specific expression pattern, the sbeⅡa promoter (3094 bp in length) was cloned using APCR and sequenced. The effect of a series of deletions was studied using a GUS transient assay system. Results showed that the 3094 bp se-quence (sbe.g construct) exhibited full stable promoting ac-tivity and that the activities of 5′ or 3′ deletions reduced levels of GUS expression. Some constructs with internal dele-tions showed only weak activity, however, sbe.e, with a dele-tion from -1579—-1210 bp resulted in higher levels of ex-pression than the full-length promoter sequence, sbe.g. This indicates that motifs such as the -300 bp element, G-box and/or P-box act as positive elements and are necessary in determining the promoters endosperm-specific pattern and that negative repressor elements or motifs may also be pre-sent within the -1579—-1210 bp sequence. The age of wheat endosperm tissue used in the GUS-transient assay system is shown to be of significant importance.展开更多
文摘Starch, the main component of the wheat grain, is the product of a complex biochemical pathway. The sbeⅡa gene plays a key role in controlling the synthesis of starch, in particular, the biosynthesis of amylopectin, in maturing wheat grain. To investigate its regulatory mechanisms and endosperm-specific expression pattern, the sbeⅡa promoter (3094 bp in length) was cloned using APCR and sequenced. The effect of a series of deletions was studied using a GUS transient assay system. Results showed that the 3094 bp se-quence (sbe.g construct) exhibited full stable promoting ac-tivity and that the activities of 5′ or 3′ deletions reduced levels of GUS expression. Some constructs with internal dele-tions showed only weak activity, however, sbe.e, with a dele-tion from -1579—-1210 bp resulted in higher levels of ex-pression than the full-length promoter sequence, sbe.g. This indicates that motifs such as the -300 bp element, G-box and/or P-box act as positive elements and are necessary in determining the promoters endosperm-specific pattern and that negative repressor elements or motifs may also be pre-sent within the -1579—-1210 bp sequence. The age of wheat endosperm tissue used in the GUS-transient assay system is shown to be of significant importance.
