ABSTRACT
Vascular-resided bacterial and fungal diseases have caused a great deal of yield loss and quality reduction in crop production world-wide. For genetic engineering of crops resistant to these diseases, it is disirable to have a strong and vascular-specific promoter. This article reviews the progress in identification of vascular-specific promoters and its function. To date, roughly twenty vascular-specific promoters have been documented. The cis-elements and motifs have been studied in detail for the promoters of bean phenylalanine ammonia lyase (PAL2), bean glycine-rich protein (grp 1.8) and Arabidopsis profilin2 (pfn2) in particular.The motif of vs-1 (CATGCTCCGTTGGATGTGGAAGACAGCA) found in grp 1.8 promoter was a cis-element that specificically bind to a transcription activation factor VSF-1 protein (one of the bZIP proteins). Mutation of vs-1 prevented it from binding to VSF-1 that resulted in abolishing the vascular-specific expresson of gus gene. Motifs of AC-I and AC-II found in PAL2 promoter were also found to be essential for vascular-specific expression. In our laboratory we have dissected pfn2 promoter into three domains (A, B, C) through 5'-deletion analysis. In this promoter we have identified two core sequences of ACGT that is commonly found in the binding sites of bZIP protein, the most abundent transcription factor existed in plants. In additon, the pfn2 promoter also contains an AC- I like sequence (CCACCTAC) that is similar to the AC- I motif (CCCACCTACC) found in PAL2 promoter. These promoters and cis-elements may have a wide range of potential applications to the genetic improvement of crops resistant to vascular diseases.