Identification and Functional Analysis of Phosphoproteins Regulated by Auxin in Arabidopsis Roots
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The phytohormone auxin modulates diverse aspects of plant growth and development. Protein phosphorylation is believed to play a key role in regulating auxin-mediated responses. To determine the phosphoproteins affected by auxin in Arabidopsis, we used phospho-specific antibodies to analyze their profiles on two-dimensional gels, then identified them by mass spectrometry. We found two phosphoproteins, enolase and the beta subunit of succinyl-CoA synthetase (SCS-beta), and noted that their phosphorylation was increased by auxin. To investigate their importance in auxin-mediated processes, we characterized Arabidopsis knockout mutants of the two genes. A homozygous null mutation in the gene for SCS-beta conferred embryo lethality. The enolase knockout mutants showed defects in root development similar to those of auxin-related mutants such as alf3 and xbat32. Therefore, we suggest that enolase is involved in auxin-regulated processes.
KeywordsArabidopsis Auxin Enolase Phosphorylation Succinyl-CoA synthetase
Enolase knockout mutant
Succinyl-CoA synthetase beta subunit
We thank Drs. Din Ma, Zhaohua Peng, and Kenneth Willeford for critical reading of the manuscript and Dr. Tibor Pechan for help with mass spectrometry. This research was partially supported by start-up funds from Mississippi State University and by the US National Science Foundation (MCB0505458). Zenglan Wang’s visit to Mississippi State University was partially supported by the National Basic Research Program of China (No. 2006CB100104). This article was approved for publication as No. J-11393 of the Mississippi Agricultural and Forestry Experiment Station.
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