Association of proteomics changes with Al-sensitive root zones in switchgrass

In this project, we report on aluminum (Al)-induced root proteomic changes in switchgrass. After growth in a hydroponic culture system supplemented with 400μM of Al, plants began to show signs of physiological stress such as a reduction in photosynthetic rate. At this time, the basal 2‐cm long root tips were harvested and divided into two segments, each of 1‐cm in length, for protein extraction. Al-induced changes in proteomes were identified using tandem mass tags mass spectrometry (TMT-MS)-based quantitative proteomics analysis. A total of 216 proteins (approximately 3.6% of total proteins) showed significant differences between non-Al treated control and treated groups with significant fold change (twice the standard deviation; FDR adjusted p-value, q<0.05). The basal root tip tissues expressed more dramatic proteome changes (164 significantly changed proteins; 3.9% of total proteins quantified) compared to the elongation/maturation zones (52 significantly changed proteins, 1.1% of total proteins quantified). Significantly changed proteins from the basal-1cm root apex tissues were clustered into 25 biological pathways, three proteins in cell cycles were all at a reduced abundance level compared to the non-treated control group. In the root elongation and maturation zone tissues, the identified proteins were placed into 18 pathways, proteins in secondary cell wall formation (lignin biosynthesis) were identified. Several STRING protein interaction networks were developed for these Al-induced significantly changed proteins. This study has identified a large number of Al-responsive proteins, including transcription factors, which will be used for exploring new Al tolerance genes and mechanisms.