The promoter from the rice nuclear gene encoding chloroplast aldolase confers mesophyll-specific and light-regulated expression in transgenic tobacco.

The rice genome contains at least four separate loci that encode aldolase isozymes. Among these, the aldolase P (AldP) gene, a nuclear gene coding for chloroplast aldolase, is expressed predominantly in the leaf blade mesophyll cells in rice. To dissect promoter elements that regulate such tissue- or cell type-specific expression, we constructed various AldP promoter-beta-glucuronidase (GUS) fusion genes and transferred them into Nicotiana tabacum (tobacco) plants. Analysis of GUS activities in the transgenic tobacco revealed the presence of at least two elements within 2.0 kb AldP promoter region. One is located within the segment from position -2.0 kb to -1.2 kb and acts as a negative element. The other is a positive element located between -1.2 kb and -0.31 kb that confers developmentally regulated, mesophyll cell-specific expression. In addition, the 1.2 kb rice promoter segment flanking the transcription start site contains an element(s) that serves as target for light induction in tobacco. The results suggest that the AldP gene promoter of rice, a monocot promoter, can function in an essentially physiological manner in the dicot tobacco plant.