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Title: Proteomic Responses in Arabidopsis thaliana Seedlings Treated with Ethylene

item CHEN, RUIQIANG - University Of Maryland
item BINDER, BRAD - University Of Maryland
item Garrett, Wesley
item Tucker, Mark
item Cooper, Bret
item CHANG, CAREN - University Of Maryland

Submitted to: Molecular Biosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/2011
Publication Date: 6/29/2011
Citation: Chen, R., Binder, B.M., Garrett, W.M., Tucker, M.L., Cooper, B., Chang, C. 2011. Proteomic Responses in Arabidopsis thaliana Seedlings Treated with Ethylene. Molecular Biosystems. 7:2637-2650.

Interpretive Summary: Ethylene is an important gas that induces fruit ripening and plant development. The receptors in plant cells that identify ethylene have been identified and it is known that the receptors affect two other proteins, CTR1 and EIN2, that transmit a molecular signal that tells the plant cell to respond to ethylene. Other than that, little is known about other proteins involved in transmitting signals, and little is known about the proteins responsible for cellular changes like leaf development. To find other, involved proteins, seedlings of the model plant Arabidopsis thaliana were exposed to ethylene gas, and mass spectrometry was used to identify thousands of proteins by their mass and to measure the amounts of those proteins in seedlings. Proteins that were identified help the plant transmit the ethylene signal, produce more ethylene, resist stress and undergo cellular growth. These results provide new insight into ethylene-controlled regulatory mechanisms in plant cells. These data are most likely to influence scientists at universities, government agencies and companies who are studying fruit ripening and plant development and who are trying to better control these processes in order to produce higher quality fruits and vegetables.

Technical Abstract: Ethylene (ET) is a volatile plant growth hormone that most famously modulates fruit ripening, but it also controls plant growth, development and stress responses. In Arabidopsis thaliana, ET is perceived by receptors in the endoplasmic reticulum, and a signal is transduced through a protein kinase, the central regulator EIN2 and several transcription factors (TFs). It is known that some early steps of signal transduction are regulated at the proteomic level, but gaps in knowledge remain. To explore initial proteomic changes on a large scale, we treated etiolated A. thaliana seedlings grown in an ET biosynthesis inhibitor with 100 ppm ET for 3 hours and used mass spectrometry to identify proteins from microsomal membrane preparations. We compared 3,814 proteins from both ET-treated and untreated samples, and 304 showed significant accumulation changes as determined by the summed spectral counting method. The proteins with increased accumulation were involved in ET biosynthesis, cell morphogenesis, oxidative stress and vesicle secretion while those with decreased accumulation were ribosomal proteins and proteins positively regulated by brassinosteroid, another hormone involved in cell elongation. Several proteins, including EIN2, appeared to be differentially phosphorylated upon ET treatment, which suggests that the activity or stability of these proteins may be controlled by phosphorylation in ET response. TUA3/5, an alpha-tubulin component of microtubules that contribute to cellular morphological change, exhibited both increased accumulation and differential phosphorylation upon ET-treatment, and tua3/5 mutant plants exhibited an altered ET-response phenotype. Overall, the data indicate that ET perception leads to rapid change at the proteomic level, and the data serve as a foundation for exploring ET-mediated signaling through systems biology.