Effects of Fe and Mn deficiencies on the protein profiles of tomato ( Solanum lycopersicum ) xylem sap as revealed by shotgun analyses

Abstract

The aim of this work was to study the effects of Fe and Mn deficiencies on the xylem sap proteome of tomato using a shotgun proteomic approach, with the final goal of elucidating plant response mechanisms to these stresses. This approach yielded 643 proteins reliably identified and quantified with 70% of them predicted as secretory. Iron and Mn deficiencies caused statistically significant and biologically relevant abundance changes in 119 and 118 xylem sap proteins, respectively. In both deficiencies, metabolic pathways most affected were protein metabolism, stress/oxidoreductases and cell wall modifications. First, results suggest that Fe deficiency elicited more stress responses than Mn deficiency, based on the changes in oxidative and proteolytic enzymes. Second, both nutrient deficiencies affect the secondary cell wall metabolism, with changes in Fe deficiency occurring via peroxidase activity, and in Mn deficiency involving peroxidase, Cu-oxidase and fasciclin-like arabinogalactan proteins. Third, the primary cell wall metabolism was affected by both nutrient deficiencies, with changes following opposite directions as judged from the abundances of several glycoside-hydrolases with endo-glycolytic activities and pectin esterases. Fourth, signaling pathways via xylem involving CLE and/or lipids as well as changes in phosphorylation and N-glycosylation also play a role in the responses to these stresses. Biological significance In spite of being essential for the delivery of nutrients to the shoots, our knowledge of xylem responses to nutrient deficiencies is very limited. The present work applies a shotgun proteomic approach to unravel the effects of Fe and Mn deficiencies on the xylem sap proteome. Overall, Fe deficiency seems to elicit more stress in the xylem sap proteome than Mn deficiency, based on the changes measured in proteolytic and oxido-reductase proteins, whereas both nutrients exert modifications in the composition of the primary and secondary cell wall. Cell wall modifications could affect the mechanical and permeability properties of the xylem sap vessels, and therefore ultimately affect solute transport and distribution to the leaves. Results also suggest that signaling cascades involving lipid and peptides might play a role in nutrient stress signaling and pinpoint interesting candidates for future studies. Finally, both nutrient deficiencies seem to affect phosphorylation and glycosylation processes, again following an opposite pattern.

Proteomic changes in the xylem sap of Brassica napus under cadmium stress and functional validation

“…The proteomic approach used in this study identified and quantified 672 proteins in the xylem sap of Brassica napus , which is considerably higher than the 69 proteins previously identified in 2-DE [6], though a recent study found 643 proteins in tomato xylem sap using a similar shotgun method [25], indicating that the shotgun label-free analysis used in this study is very sensitive. Our results showed that nearly 67% of the identified xylem proteins were classified as secretory and 33% were identified as non-secretory, which could in part be due to cytoplasmic contamination.…”

“…At 2 weeks of age, the hydroponically grown Brassica napus seedlings were exposed to 0 (control) and 10 μM Cd (treatment) for 3 days, then xylem sap samples were collected. Briefly, stems were cut with a razor blade 2–3 cm above the basal stems to collect xylem sap for 2 h. Xylem sap from the first 10 min was discarded to avoid contamination from damaged cells as described previously [25]. Xylem sap collected from 24 plants was pooled into one replicate, and a total of three replicates from 72 plants were used for each treatment.…”

“…Of the identified proteins, most are categorized as classical secretion proteins, and function annotation has revealed that they play important roles in plant growth, development, and stress responses [14–26]. With regards to stress responses, in one study, the xylem sap proteome changed in response to iron and manganese deficiencies in tomato ( Solanum lycopersicum ) [25], and in another, nitrogen under- and over-supply induced distinct protein responses in the xylem sap of maize [26].…”

Sec24C mediates a Golgi-independent trafficking pathway that is required for tonoplast localization of ABCC1 and ABCC2

“…Seeds of Col-0 and sec24c were sown in soil and watered with Hoagland nutrient solution weekly. When they were 4 weeks old, the seedlings were exposed to 0 (control) or 20 μM Cd (treatment) for 4 days, after which xylem sap samples were then collected according to a previous method 43 . Brie y, stems were cut with a razor blade 2-3 cm above the basal stems to collect xylem sap during a 2-h period.…”

Effects of Excess Manganese on the Xylem Sap Protein Profile of Tomato (Solanum lycopersicum) as Revealed by Shotgun Proteomic Analysis

“…Proteomic approaches, either gel (2-DE) or non-gel-based, are powerful tools to understand the responses that plants elicit when facing metal stresses [ 41 , 42 ]. The xylem sap proteome is expected to reflect changes in plant metabolism upon excess Mn and could also be an essential key for understanding Mn homeostasis.…”