title: Profiling of differentially expressed genes in roots of Robinia pseudoacacia during nodule development using suppressive subtractive hybridization.
abstract: BACKGROUND
  Legume-rhizobium symbiosis is a complex process that is regulated in the host plant cell through gene expression network. Many nodulin genes that are upregulated during different stages of nodulation have been identified in leguminous herbs. However, no nodulin genes in woody legume trees, such as black locust (Robinia pseudoacacia), have yet been reported.
  
  
  RESULTS
  To identify the nodulin genes involved in R. pseudoacacia-Mesorhizobium amorphae CCNWGS0123 symbiosis, a suppressive subtractive hybridization approach was applied to reveal profiling of differentially expressed genes and two subtracted cDNA libraries each containing 600 clones were constructed. Then, 114 unigenes were identified from forward SSH library by differential screening and the putative functions of these translational products were classified into 13 categories. With a particular interest in regulatory genes, twenty-one upregulated genes encoding potential regulatory proteins were selected based on the result of reverse transcription-polymerase chain reaction (RT-PCR) analysis. They included nine putative transcription genes, eight putative post-translational regulator genes and four membrane protein genes. The expression patterns of these genes were further analyzed by quantitative RT-PCR at different stages of nodule development.
  
  
  CONCLUSIONS
  The data presented here offer the first insights into the molecular foundation underlying R. pseudoacacia-M. amorphae symbiosis. A number of regulatory genes screened in the present study revealed a high level of regulatory complexity (transcriptional, post-transcriptional, translational and post-translational) that is likely essential to develop symbiosis. In addition, the possible roles of these genes in black locust nodulation are discussed.
authors.affiliation: State Key Laboratory of Crop Stress Biology in Arid Areas, College of Life Sciences, Northwest Agriculture & Forestry University, Yangling, Shaanxi, China.
authors.forename: Hongyan
authors.initials: H
authors.lastname: Chen
authors.forename: Minxia
authors.initials: M
authors.lastname: Chou
authors.forename: Xinye
authors.initials: X
authors.lastname: Wang
authors.forename: Sisi
authors.initials: S
authors.lastname: Liu
authors.forename: Feilong
authors.initials: F
authors.lastname: Zhang
authors.forename: Gehong
authors.initials: G
authors.lastname: Wei
mesh_terms: D020869:Gene Expression Profiling / Q000379:methods*; D018506:Gene Expression Regulation, Plant; D008565:Membrane Proteins / Q000235:genetics; D059128:Mesorhizobium / Q000502:physiology; D009693:Nucleic Acid Hybridization; D010940:Plant Proteins / Q000235:genetics; D018517:Plant Roots / Q000235:genetics* / Q000382:microbiology*; D031301:Robinia / Q000235:genetics* / Q000382:microbiology*; D013559:Symbiosis
chemical_list: D008565:Membrane Proteins; D010940:Plant Proteins; C045625:nodulin