The present invention relates to genetic constructs, which can be used in the preparation of transgenic plants. The constructs can have the ability of reducing nitrate concentration in the plant, in particular the plant's leaves. The invention extends to plant cells transformed with such constructs, and to the transgenic plants themselves. The invention also relates to methods of producing transgenic plants, and to methods of reducing nitrate content in plants. The invention also relates to harvested plant leaves, for example tobacco leaves, that have been transformed with the genetic constructs, and to various tobacco articles, such as smoking articles, comprising such harvested plant leaves.