A proteomics study of auxin effects in Arabidopsis thaliana.

Many phytohormones regulate plant growth and development through modulating protein degradation. In this study, a proteome study based on multidimensional non-gel shotgun approach was performed to analyze the auxin-induced protein degradation via ubiquitin-proteasome pathway of Arabidopsis thaliana, with the emphasis to study the overall protein changes after auxin treatment (1 nM or 1 µM indole-3-acetic acid for 6, 12, or 24 h). More than a thousand proteins were detected by using label-free shotgun method, and 386 increased proteins and 370 decreased ones were identified after indole-3-acetic acid treatment. By using the auxin receptor-deficient mutant, tir1-1, as control, comparative analysis revealed that 69 and 79 proteins were significantly decreased and increased, respectively. Detailed analysis showed that among the altered proteins, some were previously reported to be associated with auxin regulation and others are potentially involved in mediating the auxin effects on specific cellular and physiological processes by regulating photosynthesis, chloroplast development, cytoskeleton, and intracellular signaling. Our results demonstrated that label-free shotgun proteomics is a powerful tool for large-scale protein identification and the analysis of the proteomic profiling of auxin-regulated biological processes will provide informative clues of underlying mechanisms of auxin effects. These results will help to expand the understanding of how auxin regulates plant growth and development via protein degradation.