Senior Research Biologist US Army Engineer Research and Development Center Vicksburg, Mississippi
Body of Abstract: Gene silencing (GS) is a molecular mechanism responsible for suppressing gene expression at both transcriptional and post-transcriptional levels in plant cells. Many GS-based biotechnologies have been developed by harnessing these natural bioprocesses for pest control and gene therapies. However, application of GS biotechnologies to invasive plant control has not been widely explored. To develop innovative biotechnologies for management of invasive common reed (Phragmites australis subsp. australis), we designed and tested multiple classes of species- and gene-specific GS agents (GSAs), including artificial microRNA, double-stranded RNA, non-modified antisense oligonucleotides, engineered plasmids, and viral vectors. We also screened a variety of nanoparticles as potential nanocarriers to enhance the delivery of synthetic GSAs and the efficiency of interruption or suppression of target gene expression. Gene expression was determined using quantitative reverse transcription polymerase chain reaction (qRT-PCR), whereas phenotypic changes were either visually observed or measured for photosynthesis parameters using an LI-600 fluorometer. Our results showed that the designed GSAs, with or without a nanocarrier, significantly inhibited the expression of enzyme-coding, herbicide-target genes such as AHAS (acetohydroxyacid synthase), EPSPS (5-enolpyruvylshikimate-3-phosphate synthase), HPPD (4-hydroxyphenylpyruvate dioxygenase), and PDS (phytoene desaturase), as well as stress/defense-related non-herbicide-target genes such as HSP70 (heat shock protein 70). We also observed expected phenotypic changes in some of the GSA-treated plants. Currently, we are establishing the effective application rates for select GSA-nanocarrier pairs and designing cocktails of multiple GSAs. Our study demonstrates that the GS-based biotechnologies hold great promise to produce next-generation bioherbicides.