First you need to identify the exact position of promoter, you can take +300 bp upstream sequences prior to start codon from public database then design your primers forward one start from the 300 bp starting position and the reverse one 20 bp before starting the start codon (ATG). Using these primers you try to PCR amplify of your target plasmid and proceed your cloning.

Dear Kalyan,

The GUS gene is located into pBI101.2 vector just after the multiple cloning site. The sequence to be used as your insert, is just the 5' flanking region of your intended gene which covers the promoter sequence (not even a single nucleutide of the gene sequense itself).

It worth mentioning that Seamless cloning methods are now available for more accurate promoter studies.

Regards.