Premature polyadenylation at multiple sites within a Bacillus thuringiensis toxin gene-coding region

Area of Science:

• Plant Molecular Biology
• Gene Expression Regulation
• Biotechnology

Background:

• Foreign gene expression in plants can be limited even with strong promoters.
• Bacillus thuringiensis (B.t.) cry genes, encoding insecticidal toxins, are poorly expressed in plants.
• Understanding these limitations is crucial for improving crop protection technologies.

Purpose of the Study:

• To investigate the mechanisms limiting the expression of the B.t. toxin gene, cryIA(c), in tobacco (Nicotiana tabacum).
• To identify the causes of low mRNA accumulation for the cryIA(c) gene in transformed plant cells.

Main Methods:

• Analysis of short, polyadenylated transcripts in transformed tobacco cell lines.
• Treatment with cycloheximide to assess transcript stability.
• Hybridization, reverse-transcriptase polymerase chain reaction, and RNase-H digestion to identify polyadenylation sites.
• Use of a chimeric gene to identify additional polyadenylation sites.

Main Results:

• Transformed tobacco cells accumulated short, polyadenylated cryIA(c) transcripts.
• Cycloheximide treatment increased the abundance of these transcripts, suggesting instability.
• Multiple premature polyadenylation sites were identified within the B.t.-toxin-coding region.
• A fourth polyadenylation site was confirmed using a chimeric gene construct.

Conclusions:

• Premature polyadenylation is a significant factor limiting foreign gene expression in plants.
• This finding provides a novel explanation for poor cry gene expression in transgenic crops.
• Further research into plant polyadenylation mechanisms is essential for both fundamental science and applied biotechnology.