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Glyphosate's impact on vegetative growth in leafy spurge identifies molecular processes and hormone cross-talk associated with increased branching.

ABSTRACT: Leafy spurge (Euphorbia esula) is a perennial weed that is considered glyphosate tolerant, which is partially attributed to escape through establishment of new vegetative shoots from an abundance of underground adventitious buds. Leafy spurge plants treated with sub-lethal concentrations of foliar-applied glyphosate produce new vegetative shoots with reduced main stem elongation and increased branching. Processes associated with the glyphosate-induced phenotype were determined by RNAseq using aerial shoots derived from crown buds of glyphosate-treated and -untreated plants. Comparison between transcript abundance and accumulation of shikimate or phytohormones (abscisic acid, auxin, cytokinins, and gibberellins) from these same samples was also done to reveal correlations.Transcriptome assembly and analyses confirmed differential abundance among 12,918 transcripts (FDR???0.05) and highlighted numerous processes associated with shoot apical meristem maintenance and stem growth, which is consistent with the increased number of actively growing meristems in response to glyphosate. Foliar applied glyphosate increased shikimate abundance in crown buds prior to decapitation of aboveground shoots, which induces growth from these buds, indicating that 5-enolpyruvylshikimate 3-phosphate (EPSPS) the target site of glyphosate was inhibited. However, abundance of shikimate was similar in a subsequent generation of aerial shoots derived from crown buds of treated and untreated plants, suggesting EPSPS is no longer inhibited or abundance of shikimate initially observed in crown buds dissipated over time. Overall, auxins, gibberellins (precursors and catabolites of bioactive gibberellins), and cytokinins (precursors and bioactive cytokinins) were more abundant in the aboveground shoots derived from glyphosate-treated plants.Based on the overall data, we propose that the glyphosate-induced phenotype resulted from complex interactions involving shoot apical meristem maintenance, hormone biosynthesis and signaling (auxin, cytokinins, gibberellins, and strigolactones), cellular transport, and detoxification mechanisms.

SUBMITTER: Dogramac? M

PROVIDER: S-EPMC4437557 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Glyphosate's impact on vegetative growth in leafy spurge identifies molecular processes and hormone cross-talk associated with increased branching.

Doğramacı Münevver M Foley Michael E ME Horvath David P DP Hernandez Alvaro G AG Khetani Radhika S RS Fields Christopher J CJ Keating Kathleen M KM Mikel Mark A MA Anderson James V JV

BMC genomics 20150519

<h4>Background</h4>Leafy spurge (Euphorbia esula) is a perennial weed that is considered glyphosate tolerant, which is partially attributed to escape through establishment of new vegetative shoots from an abundance of underground adventitious buds. Leafy spurge plants treated with sub-lethal concentrations of foliar-applied glyphosate produce new vegetative shoots with reduced main stem elongation and increased branching. Processes associated with the glyphosate-induced phenotype were determined ...[more]

PMID: 25986459

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Project description:New shoot growth from underground adventitious buds of leafy spurge is critical for survival of this invasive perennial weed after episodes of severe abiotic stress. Because global climate change is expected to increase abiotic stress, such as dehydration, objectives of this study include examining the impact that dehydration stress has on molecular mechanisms associated with vegetative reproduction. Greenhouse plants were exposed to mild- (3-day), intermediate- (7-day), severe- (14-day) and extended- (21-day) dehydration treatments, prior to decapitation of aerial tissue and rehydration of soil to induce new vegetative shoot growth. Compared to well-watered control plants, mild-dehydration accelerated new vegetative shoot growth but intermediate- and severe-dehydration treatments both delayed and reduced shoot growth, and 21-day dehydration treatment inhibited initiation of new vegetative shoots and was considered a lethal treatment. Overall, transcriptome profiles revealed that 2109 genes were differentially-expressed (P<0.05) in crown buds in response to the various dehydration treatments. Sub-network enrichment analyses identified central hubs of over-represented genes involved in processes such as hormone responses and signaling (e.g., ABA, auxin, ethylene, GA, and JA), response to abiotic stress (DREB1A/2A) and light (PIF3), phosphorylation (CLV1, MPK3/4/6, SOS2), gene silencing (miRNA156/172a), circadian regulation (CRY2, LHY, PHYA/B), and flowering (AGL8/20, AP2, FLC). Further, results from this and previous studies highlight HY5, MAF3, MYB-like/RVE1 and RD22 as molecular markers for endodormancy in crown buds of leafy spurge. Early response to dehydration also highlighted involvement of upstream ethylene and jasmonate signaling, whereas longer-term dehydration impacted ABA signaling. The identification of conserved ABRE- and MYC-consensus, cis-acting elements in the promoter of a leafy spurge gene similar to Arabidopsis MYB-like/RVE1 (AT5G17300) implicates a potential role for ABA signaling in its dehydration-induced expression. Response of these molecular mechanisms to dehydration-stress provides insights on the ability of invasive perennial weeds to adapt and survive under harsh environments, which provide new insights for addressing future management practices.

Project description:Quantitative real-time polymerase chain reaction (qRT-PCR) is the most important tool in measuring levels of gene expression due to its accuracy, specificity, and sensitivity. However, the accuracy of qRT-PCR analysis strongly depends on transcript normalization using stably expressed reference genes. The aim of this study was to find internal reference genes for qRT-PCR analysis in various experimental conditions for seed, adventitious underground bud, and other organs of leafy spurge. Eleven candidate reference genes (BAM4, PU1, TRP-like, FRO1, ORE9, BAM1, SEU, ARF2, KAPP, ZTL, and MPK4) were selected from among 171 genes based on expression stabilities during seed germination and bud growth. The other ten candidate reference genes were selected from three different sources: (1) 3 stably expressed leafy spurge genes (60S, bZIP21, and MD-100) identified from the analyses of leafy spurge microarray data; (2) 3 orthologs of Arabidopsis "general purpose" traditional reference genes (GAPDH_1, GAPDH_2, and UBC); and (3) 4 orthologs of Arabidopsis stably expressed genes (UBC9, SAND, PTB, and F-box) identified from Affymetrix ATH1 whole-genome GeneChip studies. The expression stabilities of these 21 genes were ranked based on the C(T) values of 72 samples using four different computation programs including geNorm, Normfinder, BestKeeper, and the comparative ?C(T) method. Our analyses revealed SAND, PTB, ORE9, and ARF2 to be the most appropriate reference genes for accurate normalization of gene expression data. Since SAND and PTB were obtained from 4 orthologs of Arabidopsis, while ORE9 and ARF2 were selected from 171 leafy spurge genes, it was more efficient to identify good reference genes from the orthologs of other plant species that were known to be stably expressed than that of randomly testing endogenous genes. Nevertheless, the two newly identified leafy spurge genes, ORE9 and ARF2, can serve as orthologous candidates in the search for reference genes from other plant species.

Dataset Information

Glyphosate's impact on vegetative growth in leafy spurge identifies molecular processes and hormone cross-talk associated with increased branching.

Publications

Glyphosate's impact on vegetative growth in leafy spurge identifies molecular processes and hormone cross-talk associated with increased branching.

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