Proteomic Analysis of Microtubule Interacting Proteins over the Course of Xylem Tracheary Element Formation in Arabidopsis

摘要

Plant vascular cells, or tracheary elements (), rely on circumferential secondary cell wall thickenings to maintain sap flow. The patterns in which thickenings are organized vary according to the underlying microtubule bundles that guide wall deposition. To identify microtubule interacting proteins present at defined stages of differentiation, we exploited the synchronous differentiation of in Arabidopsis thaliana suspension cultures. Quantitative proteomic analysis of microtubule pull-downs, using ratiometric ¹⁴N/¹⁵N labeling, revealed 605 proteins exhibiting differential accumulation during differentiation. Microtubule interacting proteins associated with membrane trafficking, protein synthesis, DNA/RNA binding, and signal transduction peaked during secondary cell wall formation, while proteins associated with stress peaked when approaching cell death. In particular, CELLULOSE SYNTHASE-INTERACTING PROTEIN1, already associated with primary wall synthesis, was enriched during secondary cell wall formation. RNAi knockdown of genes encoding several of the identified proteins showed that secondary wall formation depends on the coordinated presence of microtubule interacting proteins with nonoverlapping functions: cell wall thickness, cell wall homogeneity, and the pattern and cortical location of the wall are dependent on different proteins. Altogether, proteins linking microtubules to a range of metabolic compartments vary specifically during differentiation and regulate different aspects of wall patterning.