|HERNANDEZ, ALVARO - University Of Illinois|
|KHETANI, RADHIKA - University Of Illinois|
|FIELDS, CHRISTOPHER - University Of Illinois|
|KEATING, KATHLEEN - University Of Illinois|
|MIKEL, MARK - University Of Illinois|
Submitted to: Biomed Central (BMC) Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2015
Publication Date: 5/19/2015
Citation: Dogramaci, M., Foley, M.E., Horvath, D.P., Hernandez, A.G., Khetani, R.S., Fields, C.J., Keating, K.M., Mikel, M.A., Anderson, J.V. 2015. Glyphosate’s impact on vegetative growth in leafy spurge identifies molecular processes and hormone cross-talk associated with increased branching. Biomed Central (BMC) Genomics. 16:395. https://doi.org/10.1186/S12864-015-1627-9.
Interpretive Summary: Leafy spurge is a perennial weed that is considered glyphosate tolerant, partially due to new shoot growth from an abundance of underground adventitious buds. Thus, long term control of leafy spurge requires continual herbicide applications. New vegetative shoots derived from underground adventitious buds of plants treated with sub-lethal rates of foliar applied glyphosate have reduced main stem elongation and increased branching. The effects of sub-lethal glyphosate rates on molecular mechanisms associated with this glyphosate-induced growth pattern were determined using next-generation sequencing technologies and bioinformatics analysis. These studies identified numerous molecular processes associated with shoot apical meristem maintenance and stem growth. Comparisons between abundance of plant growth regulators (hormones) and molecular processes suggest hormone transport, signaling, and cross-talk play a role in the glyphosate-induced phenotypes. Based on the results of this study, we propose that the glyphosate-induced phenotypes showing reduced stem elongation and increased branching are the result of glyphosate’s effects on molecular processes associated with cellular transport in new vegetative shoots, which impacts plant hormone abundance and signaling, and meristem maintenance.
Technical Abstract: Leafy spurge (Euphorbia esula) is a perennial weed that is considered glyphosate tolerant. Tolerance is partly attributed to escape through establishment of new vegetative shoots from an abundance of underground adventitious buds. Sub-lethal concentrations of foliar applied glyphosate resulted in new vegetative shoots with reduced main stem elongation and increased branching. Glyphosate’s impact on molecular processes associated with the glyphosate-induced phenotype was determined by RNAseq using a subsequent generation of aerial shoots derived from crown buds of glyphosate-treated and -untreated leafy spurge. Transcriptome assembly and analyses identified differential abundance among 12,918 transcripts (FDR = 0.05). Analysis of the global transcriptome data identified numerous processes associated with shoot apical meristem maintenance and stem growth, which is consistent with actively growing meristems. A comparison of transcript abundance and accumulation of shikimate and phytohormones from these same samples was done to elucidate interactions. Although abundance of shikimate was significantly increased in crown buds in response to glyphosate prior to growth-induction by decapitation of treated aerial tissue, abundance of shikimate was similar in a subsequent generation of aerial shoots generated from crown buds of treated and untreated plants. However, the results suggest transcripts involved in auxin transport, signaling, and cross-talk among auxin, cytokinins and gibberellins likely play a role in the glyphosate-induced phenotypes. We propose that glyphosate or its metabolites affect molecular processes associated with cellular transport, which impacts hormone abundance and signaling, meristem maintenance, and detoxification processes leading to reduced main stem elongation and increased branching phenotypes.