title: Root secretion of defense-related proteins is development-dependent and correlated with flowering time.
abstract: Proteins found in the root exudates are thought to play a role in the interactions between plants and soil organisms. To gain a better understanding of protein secretion by roots, we conducted a systematic proteomic analysis of the root exudates of Arabidopsis thaliana at different plant developmental stages. In total, we identified 111 proteins secreted by roots, the majority of which were exuded constitutively during all stages of development. However, defense-related proteins such as chitinases, glucanases, myrosinases, and others showed enhanced secretion during flowering. Defense-impaired mutants npr1-1 and NahG showed lower levels of secretion of defense proteins at flowering compared with the wild type. The flowering-defective mutants fca-1, stm-4, and co-1 showed almost undetectable levels of defense proteins in their root exudates at similar time points. In contrast, root secretions of defense-enhanced cpr5-2 mutants showed higher levels of defense proteins. The proteomics data were positively correlated with enzymatic activity assays for defense proteins and with in silico gene expression analysis of genes specifically expressed in roots of Arabidopsis. In conclusion, our results show a clear correlation between defense-related proteins secreted by roots and flowering time.
authors.affiliation: Department of Horticulture and Landscape Architecture and Center for Rhizosphere Biology, Colorado State University, Fort Collins, Colorado 80523, USA.
authors.forename: Clelia
authors.initials: C
authors.lastname: De-la-Peña
authors.forename: Dayakar V
authors.initials: DV
authors.lastname: Badri
authors.forename: Zhentian
authors.initials: Z
authors.lastname: Lei
authors.forename: Bonnie S
authors.initials: BS
authors.lastname: Watson
authors.forename: Marcelo M
authors.initials: MM
authors.lastname: Brandão
authors.forename: Marcio C
authors.initials: MC
authors.lastname: Silva-Filho
authors.forename: Lloyd W
authors.initials: LW
authors.lastname: Sumner
authors.forename: Jorge M
authors.initials: JM
authors.lastname: Vivanco
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D035264:Flowers / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism*; D040901:Proteomics
chemical_list: D010940:Plant Proteins