Amino acids induce high seed-specific expression driven by a soybean (Glycine max) glycinin seed storage protein promoter.

KEY MESSAGE: We characterize GFP expression driven by a soybean glycinin promoter in transgenic soybean. We demonstrate specific amino acid-mediated induction of this promoter in developing soybean seeds in vitro. In plants, gene expression is primarily regulated by promoter regions which are located upstream of gene coding sequences. Promoters allow transcription in certain tissues and respond to environmental stimuli as well as other inductive phenomena. In soybean, seed storage proteins (SSPs) accumulate during seed development and account for most of the monetary and nutritional value of this crop. To better study the regulatory functions of a SSP promoter, we developed a cotyledon culture system where media and media addenda were evaluated for their effects on cotyledon development and promoter activity. Stably transformed soybean events containing a glycinin SSP promoter regulating the green fluorescent protein (GFP) were generated. Promoter activity, as visualized by GFP expression, was only observed in developing in planta seeds and in vitro-cultured isolated embryos and cotyledons from developing seeds when specific media addenda were included. Asparagine, proline, and especially glutamine induced glycinin promoter activity in cultured cotyledons from developing seeds. Other amino acids did not induce the glycinin promoter. Here, we report, for the first time, induction of a reintroduced glycinin SSP promoter by specific amino acids in cotyledon tissues during seed development.

Transient Transformation Using Particle Bombardment for Gene Expression Analysis.

Transient transformation or transient expression results in rapid and fleeting gene expression. This approach is often used as a first-tier screening tool for evaluation of components that affect gene expression. Here, we describe the use of particle bombardment of lima bean cotyledons with constructs containing the green fluorescent protein (gfp) coding region for evaluation of promoter components that influence gene expression. Although this approach is conceptually quite simple, this lima bean transient expression system may not work well, if our methods and notes are not carefully read and followed. Our laboratory has successfully optimized this method over the past 10 years, resulting in a transient expression system, which works like no other that we have seen.