Soybean Response to Plant Growth Regulator Herbicides: Field Evaluation and Expression Analysis of Candidate Auxin -Responsive Genes
A lack of diagnostic tools specific to PGR herbicides often result in difficulty and confusion when responding to reported cases of soybean symptoms resembling PGR herbicide injury. PGR herbicides overstimulate the auxin hormonal pathway and induce gene expression. Identifying genes specifically induced by PGR herbicides may result in a diagnostic assay that identifies or rules out PGR herbicides as the causal agent of abnormal foliar symptoms in soybean. By examining genes induced in soybean by auxin, GH3, a primary auxin-responsive gene, was found to be strongly induced by PGR herbicides in soybean leaves at both the RNA and protein levels. Proteomic analysis identified three other proteins that were up-regulated in response to dicamba in soybean leaves, although these proteins are probably not candidates for markers specific to PGR herbicide injury. Time course and dose-response analysis of GH3 expression indicate that a diagnostic assay would be effective for a limited time after exposure, and an assay based on GH3 protein expression may not detect expression in response to lower herbicide doses. However, GH3 expression was highly specific for PGR herbicides and was dose-dependent. GH3 has excellent potential as a specific molecular indicator for PGR herbicide injury in soybean.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign