Apoplast proteome reveals that extracellular matrix contributes to multistress response in poplar.
BACKGROUND
Riverine ecosystems, highly sensitive to climate change and human activities, are characterized by rapid environmental change to fluctuating water levels and siltation, causing stress on their biological components. We have little understanding of mechanisms by which riverine plant species have developed adaptive strategies to cope with stress in dynamic environments while maintaining growth and development.


RESULTS
We report that poplar (Populus spp.) has evolved a systems level "stress proteome" in the leaf-stem-root apoplast continuum to counter biotic and abiotic factors. To obtain apoplast proteins from P. deltoides, we developed pressure-chamber and water-displacement methods for leaves and stems, respectively. Analyses of 303 proteins and corresponding transcripts coupled with controlled experiments and bioinformatics demonstrate that poplar depends on constitutive and inducible factors to deal with water, pathogen, and oxidative stress. However, each apoplast possessed a unique set of proteins, indicating that response to stress is partly compartmentalized. Apoplast proteins that are involved in glycolysis, fermentation, and catabolism of sucrose and starch appear to enable poplar to grow normally under water stress. Pathogenesis-related proteins mediating water and pathogen stress in apoplast were particularly abundant and effective in suppressing growth of the most prevalent poplar pathogen Melampsora. Unexpectedly, we found diverse peroxidases that appear to be involved in stress-induced cell wall modification in apoplast, particularly during the growing season. Poplar developed a robust antioxidative system to buffer oxidation in stem apoplast.


CONCLUSIONS
These findings suggest that multistress response in the apoplast constitutes an important adaptive trait for poplar to inhabit dynamic environments and is also a potential mechanism in other riverine plant species.
Department of Forestry, Mississippi State University, Mississippi State, MS 39762, USA.
Olga
O
Pechanova
Chuan-Yu
CY
Hsu
Joshua P
JP
Adams
Tibor
T
Pechan
Lindsay
L
Vandervelde
Jenny
J
Drnevich
Sara
S
Jawdy
Ardeshir
A
Adeli
Jeffrey C
JC
Suttle
Amanda M
AM
Lawrence
Timothy J
TJ
Tschaplinski
Armand
A
Séguin
Cetin
C
Yuceer
D000975:Antioxidants / Q000378:metabolism; D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism; D016000:Cluster Analysis; D055864:Droughts; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D053263:Gene Regulatory Networks / Q000187:drug effects; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism*; D008954:Models, Biological; D010802:Phylogeny; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D032107:Populus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D020543:Proteome / Q000378:metabolism*; D040901:Proteomics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013312:Stress, Physiological / Q000187:drug effects; D014867:Water / Q000494:pharmacology
D000975:Antioxidants; D010940:Plant Proteins; D020543:Proteome; D012333:RNA, Messenger; D014867:Water