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Title: Monitoring wheat mitochondrial compositional and respiratory changes using Fourier transform mid-infrared spectroscopy in response to agrochemical treatments

Author
item PEDERSEN, MATT - University Of Nebraska
item WEGNER, CASEY - University Of Michigan
item PHANSAK, PIYAPORN - Nakhon Phanom University, Thailand
item Sarath, Gautam
item GAUSSOIN, ROCH - University Of Nebraska
item SCHLEGEL, VICKI - University Of Nebraska

Submitted to: Spectrochimica Acta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2016
Publication Date: 10/18/2016
Publication URL: http://handle.nal.usda.gov/10113/63274
Citation: Pedersen, M., Wegner, C., Phansak, P., Sarath, G., Gaussoin, R., Schlegel, V. 2017. Detection of mitochondrial respiration changes in wheat seedlings using Fourier transform infrared spectroscopy. Spectrochimica Acta. 173:727-732.

Interpretive Summary: Mitochondria are organelles present in cells of higher organisms that are critical for aerobic respiration. During this process, mitochondria consume oxygen and produce high-energy compounds that are subsequently used to cell/organism growth and development. The functionality of mitochondria isolated from tissues has been studied by estimating the amount of oxygen consumed in a specialized vessel containing an oxygen-sensitive probe. However, this process is laborious and does not provide any details of changes occurring within mitochondria. In order to find more efficient ways to study changes occurring to mitochondrial proteins and other molecules in response to exogenous chemicals, such as fungicides, a method called Fourier transform infrared spectroscopy (FTIR) was utilized. FTIR offers a low cost, low labor, and high sample throughput means to determine molecular changes that take place in isolated mitochondria. In this study, the impact of several crop fungicides that have been documented to positively impact plant growth and development were evaluated by FTIR using isolated wheat seedling mitochondria. Results indicated that FTIR can provide a rapid means to evaluate these chemicals, and associate molecular changes occurring to mitochondrial proteins that could possibly explain their mode of action. By establishing the base line changes occurring to mitochondrial contents, it now becomes possible to evaluate how specific fungicides also improve plant performance, especially under environmental conditions that cause stress.

Technical Abstract: Fungicides and plant growth regulators can impact plant growth outside of their effects on fungal pathogens. Although many of these chemicals are inhibitors of mitochondrial oxygen uptake, information remains limited as to whether they are able tomodify other mitochondrial constituents. Fourier transformmid-infrared spectroscopy (FT-mIR) offers a high sample throughput method to comparatively and qualitatively evaluate the effects of exogenously added compounds on mitochondrial components. Therefore the objective of this study was to determine the ability of FT-mIR to detect effects mitochondrial fractions isolated from wheat (Triticum aestivum L.) seedlings in response to several agrochemical treatments, with an emphasis on fungicides. The accessed need was to develop FT-mIR analytical and statistical routines as an effective approach to differentiate spectra obtained from chemically-treated or untreated mitochondria. An NADH-dependent oxygen uptake approach was initially used as a comparative method to determine whether the fungicides (azoxystrobin, boscalid, cyazofamid, fluazinam, isopyrazam, and pyraclostrobin) and the plant growth regulator, (trinexapac-ethyl) reduced respiration inhibition on isolated mitochondria. Pyraclostrobin was themost effective inhibitor,whereas amisulbrom did not impact oxygen uptake. However, hierarchical clustering of FT-mIR spectra of isolated mitochondria treated with these different compounds separated into clades consistent with each of their expected mode of action. Analysis of the FT-mIR amide protein region indicated that amisulbrom and pyraclostrobin interacted with the isolated wheat mitochondria. Both chemicals were statistically different from the control signifying that respiration was indeed influenced by these treatments. Moreover, the entire FT-mIR region showed differences in various biological bands thereby providing additional information on mitochondria responses to agrochemicals, if so warranted.