One of the goals of plant genetic engineering is to produce a plant with desirable characteristics or traits. As such, plants have been generated where a native gene or an exogenous gene possessing a desirable characteristic is stably incorporated into the plant genome. Once incorporated, the native gene or exogenous gene is expressed. All cells of an organism contain more or less the same genetic information, yet genes are turned on and other turned off at different locations and times during the life cycle of the organism. An important component in gene expression is the promoter region. Promoters are the polynucleotide sequences upstream of a coding sequence that comprises the 5′ regulatory elements controlling gene expression in living cells. There are many types of promoters which can be classified by the intended type of control of gene expression: constitutive, tissue-specific, inducible and synthetic. Inducible expression can be controlled chemically, such as chemicals not usually found in the plant, or physical, such as drought or light. Promoters can also be classified on the basis of regulation characteristics such as those temporally or developmentally regulated. Promoters can be used as tools to regulate expression of genes of interest. Isolated promoters that function in plants are useful for modifying plant phenotypes through methods of genetic engineering.
There is still a need for promoters capable of directing expression in a tissue specific manner, for example, a root cap cell specific manner.
This is also a need for a promoter useful to analyze the process of root cap cell sloughing and for targeting to the environment products with beneficial properties for plant growth.
There is also a need to modulate gene expression by chemical treatment of a transgenic plant having been transformed with a construct comprising a chemical sensitive promoter.