Comparative analysis of Brassica napus plasma membrane proteins under phosphorus deficiency using label-free and...

Phosphorus (P) deficiency is a primary constraint for plant growth in terrestrial ecosystems. To better understand the genotypic differences in the adaptation mechanism of Brassica napus to P deficiency, we purified the plasma membrane (PM) from the roots of two genotypes: P-efficient "Eyou Changjia" and P-inefficient "B104-2". Combining label-free quantitative proteomics with the MaxQuant approach, a total of 71 proteins that significantly changed in abundances were identified in the two genotypes in response to P-free starvation, including 31 in "Eyou Changjia" and 40 in "B104-2". Based on comparative genomics study, 28 proteins were mapped to the confidence intervals of quantitative trait loci (QTLs) for P efficiency related traits. Seven decreased proteins with transporter activity were found to be located in the PM by subcellular localization analyses. These proteins involved in intracellular protein transport and ATP hydrolysis coupled proton transport were mapped to the QTL for P content and dry weight. Compared with "B104-2", more decreased proteins referring to transporter activity were found in "Eyou Changjia", showing that substance exchange was decreased in response to short-term P-free starvation. Together with the finding, more decreased proteins functioning in signal transduction and protein synthesis/degradation suggested that "Eyou Changjia" could slow the progression of growth and save more P in response to short-term P-free starvation.

P deficiency seriously limits the production and quality of B. napus. Roots absorb water and nutrients and anchor the plant in the soil. Therefore, to study root PM proteome under P stress would be helpful to understand the adaptation mechanism for P deficiency. However, PM proteome analysis in B. napus has been seldom reported due to the high hydrophobicity and low abundance of PM. Thus, we herein investigated the PM proteome alteration of roots in two B. napus genotypes, with different P deficient tolerances, in response to P-free starvation. The present study offers new insights and novel information for better understanding the adaptative response to P deficiency in B. napus.