Abstract：A cis-acting genetic element aps (amplification promoting sequence) was successfully isolated from ribosomal DNA of tobacco variety named “CuiBi No.1”. The aps encoded a complete nucleotide sequence of 440 bp, including TATA TAAATG motifs, and was rich in A/T sequences. The cloned sequence has been deposited into GenBank with accession No. FJ516382. The regulatory expression function of aps was examined by introducing it into upstream of CaMV35S promoter with GUS as a reporter gene. Southern blot result revealed that transgenic rice plants, transformed with expression cassettes, carrying the GUS gene and CaMV35S promoter in combination of aps, contained much more multiple copies when compared to those transformants without aps. The semi-quantitative RT-PCR analysis indicated that the transformants with the insertion of aps had much higher transcription levels. GUS activity quantitative analysis showed that transformants in fusion of aps had higher GUS activities with 12.07-16.03 (GUS activity /nmol MU mg protein-1min-1). The activity values were remarkable higher (*P<0.05) when compared to transformants lacking aps which had 5.32-7.01 GUS activity/nmol MU mg protein-1 min-1. Our results suggested that aps was likely to elevate the transgenic expression by increasing both target gene copy number and transcription level in rice, similar to its effects previously reported in dicot tobacco and tomato. It also suggested that aps could perform a specific function as an enhancer of transcription in monocot rice, implicating its potential application in plant genetic engineering.
