Phloem Exudate Protein Profiles during Drought and Recovery Reveal Abiotic Stress Responses in Tomato Vasculature

Abstract

Drought is the leading cause of agricultural yield loss among all abiotic stresses, and the link between water deficit and phloem protein contents is relatively unexplored. Here we collected phloem exudates from Solanum lycopersicum leaves during periods of drought stress and recovery. Our analysis identified 2558 proteins, the most abundant of which were previously localized to the phloem. Independent of drought, enrichment analysis of the total phloem exudate protein profiles from all samples suggests that the protein content of phloem sap is complex, and includes proteins that function in chaperone systems, branched-chain amino acid synthesis, trehalose metabolism, and RNA silencing. We observed 169 proteins whose abundance changed significantly within the phloem sap, either during drought or recovery. Proteins that became significantly more abundant during drought include members of lipid metabolism, chaperone-mediated protein folding, carboxylic acid metabolism, abscisic acid signaling, cytokinin biosynthesis, and amino acid metabolism. Conversely, proteins involved in lipid signaling, sphingolipid metabolism, cell wall organization, carbohydrate metabolism, and a mitogen-activated protein kinase are decreased during drought. Our experiment has achieved an in-depth profiling of phloem sap protein contents during drought stress and recovery that supports previous findings and provides new evidence that multiple biological processes are involved in drought adaptation.

Galactinol synthase 1 improves cucumber performance under cold stress by enhancing assimilate translocation

“…Ogden et al . [ 46 ] observed 169 proteins that exhibit significant changes in abundance within tomato phloem sap during periods of drought and recovery. Jakobs and Müller [ 47 ] found that aphid infestation of Tanacetum vulgare leads to changes in phloem sap chemistry.…”

Reactive Oxygen Species and Abiotic Stress in Plants

“…Luckily, the recent advances in technologies allowing large-scale “–omics” analyses accelerate this process. The studies in this Special Issue add valuable pieces of the puzzle related to stress responses by: (i) reporting novel potent regulators and the mechanisms through which they exert their effects [ 15 , 17 , 18 , 19 ]; (ii) throwing light on previously unexplored components [ 16 ] or the pathways involved in particular stress types [ 11 , 12 , 13 ]; or (iii) exploring strategies to mitigate the detrimental effects [ 14 ]. We are confident that they will inspire further productive research in the future.…”

“…One such example is phloem sap, whose dynamics in response to abiotic stress is relatively unexplored. Ogden et al [ 16 ] provided one comprehensive snapshot of the protein composition of phloem sap during drought and subsequent recovery in tomato. Using a proteomic approach (LC-MS/MS), the authors detected 2558 novel or previously described proteins, involved in various biological processes.…”

“…On the other hand, some of the remarkably downregulated proteins function in processes such as cell wall modification, ceramide metabolism, mitogen-activated protein phosphorylation, etc. [ 16 ]. These results demonstrate that plant vasculature may play an active role during drought-stress adaptation.…”

Strategies to Apply Water-Deficit Stress: Similarities and Disparities at the Whole Plant Metabolism Level in Medicago truncatula

“…In this proteomics study, Castañeda et al described the existence of a core stress responsive proteome in M. truncatula across different tissues including the phloem sap, suggesting a major role of the phloem in stress protection and antioxidant activity, especially by linking below and above ground communication in order to fine-tune stress response [ 15 ]. Other studies considering the phloem sap and different water-deficit stresses have been made in tomato [ 16 , 17 ], Plantago major [ 18 ], white clover [ 19 ], Ricinus communis [ 20 ], maize [ 21 ] and alfalfa [ 22 ].…”