title: Dehydration stress memory genes of Zea mays; comparison with Arabidopsis thaliana.
abstract: BACKGROUND
  Pre-exposing plants to diverse abiotic stresses may alter their physiological and transcriptional responses to a subsequent stress, suggesting a form of "stress memory". Arabidopsis thaliana plants that have experienced multiple exposures to dehydration stress display transcriptional behavior suggesting "memory" from an earlier stress. Genes that respond to a first stress by up-regulating or down-regulating their transcription but in a subsequent stress provide a significantly different response define the 'memory genes' category. Genes responding similarly to each stress form the 'non-memory' category. It is unknown whether such memory responses exists in other Angiosperm lineages and whether memory is an evolutionarily conserved response to repeated dehydration stresses.
  
  
  RESULTS
  Here, we determine the transcriptional responses of maize (Zea mays L.) plants that have experienced repeated exposures to dehydration stress in comparison with plants encountering the stress for the first time. Four distinct transcription memory response patterns similar to those displayed by A. thaliana were revealed. The most important contribution is the evidence that monocot and eudicot plants, two lineages that have diverged 140 to 200 M years ago, display similar abilities to 'remember' a dehydration stress and to modify their transcriptional responses, accordingly. The highly sensitive RNA-Seq analyses allowed to identify genes that function similarly in the two lineages, as well as genes that function in species-specific ways. Memory transcription patterns indicate that the transcriptional behavior of responding genes under repeated stresses is different from the behavior during an initial dehydration stress, suggesting that stress memory is a complex phenotype resulting from coordinated responses of multiple signaling pathways.
  
  
  CONCLUSIONS
  Structurally related genes displaying the same memory responses in the two species would suggest conservation of the genes' memory during the evolution of plants' dehydration stress response systems. On the other hand, divergent transcription memory responses by genes encoding similar functions would suggest occurrence of species-specific memory responses. The results provide novel insights into our current knowledge of how plants respond to multiple dehydration stresses, as compared to a single exposure, and may serve as a reference platform to study the functions of memory genes in adaptive responses to water deficit in monocot and eudicot plants.
authors.forename: Yong
authors.initials: Y
authors.lastname: Ding
authors.forename: Laetitia
authors.initials: L
authors.lastname: Virlouvet
authors.forename: Ning
authors.initials: N
authors.lastname: Liu
authors.forename: Jean-Jack
authors.initials: JJ
authors.lastname: Riethoven
authors.forename: Michael
authors.initials: M
authors.lastname: Fromm
authors.affiliation: University of Nebraska School of Biological Sciences, 1901 Vine Street, Lincoln 68588, USA. zavramova2@unl.edu.
authors.forename: Zoya
authors.initials: Z
authors.lastname: Avramova
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000502:physiology*; D005075:Biological Evolution; D003681:Dehydration; D063990:Gene Ontology; D017343:Genes, Plant; D010937:Plant Growth Regulators / Q000494:pharmacology; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014867:Water / Q000378:metabolism; D003313:Zea mays / Q000187:drug effects / Q000235:genetics* / Q000502:physiology*
chemical_list: D010937:Plant Growth Regulators; D012333:RNA, Messenger; D014157:Transcription Factors; D014867:Water