Abstract: The present invention relates to the use of DNA sequence motifs to regulate gene expression in a tissue- or developmental-specific manner in transgenic plants. The invention generally relates to the engineering and use of G-box related sequence motifs, specifically Iwt and PA motifs, which function as cis-elements of promoters, to regulate the expression of heterologous genes in transgenic plants. PA enhances high level expression in roots, low level expression in leaves and little or no expression in seeds. By contrast, Iwt confers preferential expression in seeds, but in a developmentally-regulated manner.

Abstract: The identification and cloning of the gene(s) for plant asparagine synthetase (AS), an important enzyme involved in the formation of asparagine, a major nitrogen transport compound of higher plants is described. Expression vectors constructed with the AS coding sequence may be utilized to produce plant AS; to engineer herbicide resistant plants, salt/drought tolerant plants or pathogen resistant plants; as a dominant selectable marker; or to select for novel herbicides or compounds useful as agents that synchronize plant cells in culture.The promoter for plant AS, which directs high levels of gene expression and is induced in an organ specific manner and by darkness, is also described. The AS promoter may be used to direct the expression of heterologous coding sequences in appropriate hosts.