title: Spatial distribution of transcript changes in the maize primary root elongation zone at low water potential.
abstract: BACKGROUND
  Previous work showed that the maize primary root adapts to low Psiw (-1.6 MPa) by maintaining longitudinal expansion in the apical 3 mm (region 1), whereas in the adjacent 4 mm (region 2) longitudinal expansion reaches a maximum in well-watered roots but is progressively inhibited at low Psiw. To identify mechanisms that determine these responses to low Psiw, transcript expression was profiled in these regions of water-stressed and well-watered roots. In addition, comparison between region 2 of water-stressed roots and the zone of growth deceleration in well-watered roots (region 3) distinguished stress-responsive genes in region 2 from those involved in cell maturation.
  
  
  RESULTS
  Responses of gene expression to water stress in regions 1 and 2 were largely distinct. The largest functional categories of differentially expressed transcripts were reactive oxygen species and carbon metabolism in region 1, and membrane transport in region 2. Transcripts controlling sucrose hydrolysis distinguished well-watered and water-stressed states (invertase vs. sucrose synthase), and changes in expression of transcripts for starch synthesis indicated further alteration in carbon metabolism under water deficit. A role for inositols in the stress response was suggested, as was control of proline metabolism. Increased expression of transcripts for wall-loosening proteins in region 1, and for elements of ABA and ethylene signaling were also indicated in the response to water deficit.
  
  
  CONCLUSIONS
  The analysis indicates that fundamentally different signaling and metabolic response mechanisms are involved in the response to water stress in different regions of the maize primary root elongation zone.
authors.affiliation: Division of Plant Sciences, University of Missouri, Columbia, MO 65211, USA. spollenw@missouri.edu
authors.forename: William G
authors.initials: WG
authors.lastname: Spollen
authors.forename: Wenjing
authors.initials: W
authors.lastname: Tao
authors.forename: Babu
authors.initials: B
authors.lastname: Valliyodan
authors.forename: Kegui
authors.initials: K
authors.lastname: Chen
authors.forename: Lindsey G
authors.initials: LG
authors.lastname: Hejlek
authors.forename: Jong-Joo
authors.initials: JJ
authors.lastname: Kim
authors.forename: Mary E
authors.initials: ME
authors.lastname: Lenoble
authors.forename: Jinming
authors.initials: J
authors.lastname: Zhu
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Bohnert
authors.forename: David
authors.initials: D
authors.lastname: Henderson
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Schachtman
authors.forename: Georgia E
authors.initials: GE
authors.lastname: Davis
authors.forename: Gordon K
authors.initials: GK
authors.lastname: Springer
authors.forename: Robert E
authors.initials: RE
authors.lastname: Sharp
authors.forename: Henry T
authors.initials: HT
authors.lastname: Nguyen
mesh_terms: D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D020411:Oligonucleotide Array Sequence Analysis; D018517:Plant Roots / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014867:Water / Q000378:metabolism*; D003313:Zea mays / Q000235:genetics* / Q000378:metabolism
chemical_list: D014867:Water