title: Conservation of noncoding microsatellites in plants: implication for gene regulation.
abstract: BACKGROUND
  Microsatellites are extremely common in plant genomes, and in particular, they are significantly enriched in the 5' noncoding regions. Although some 5' noncoding microsatellites involved in gene regulation have been described, the general properties of microsatellites as regulatory elements are still unknown. To address the question of microsatellites associated with regulatory elements, we have analyzed the conserved noncoding microsatellite sequences (CNMSs) in the 5' noncoding regions by inter- and intragenomic phylogenetic footprinting in the Arabidopsis and Brassica genomes.
  
  
  RESULTS
  We identified 247 Arabidopsis-Brassica orthologous and 122 Arabidopsis paralogous CNMSs, representing 491 CT/GA and CTT/GAA repeats, which accounted for 10.6% of these types located in the 500-bp regions upstream of coding sequences in the Arabidopsis genome. Among these identified CNMSs, 18 microsatellites show high conservation in the regulatory regions of both orthologous and paralogous genes, and some of them also appear in the corresponding positions of more distant homologs in Arabidopsis, as well as in other plants. A computational scan of CNMSs for known cis-regulatory elements showed that light responsive elements were clustered in the region of CT/GA repeats, as well as salicylic acid responsive elements in the (CTT)n/(GAA)n sequences. Patterns of gene expression revealed that 70-80% of CNMS (CTT)n/(GAA)n associated genes were regulated by salicylic acid, which was consistent with the prediction of regulatory elements in silico.
  
  
  CONCLUSIONS
  Our analyses showed that some noncoding microsatellites were conserved in plants and appeared to be ancient. These CNMSs served as regulatory elements involved in light and salicylic acid responses. Our findings might have implications in the common features of the over-represented microsatellites for gene regulation in plant-specific pathways.
authors.affiliation: Plant Biotechnology Research Center, Fudan-SJTU-Nottingham Plant Biotechnology R&D Center, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200030, China. zhangld@sjtu.edu.cn <zhangld@sjtu.edu.cn>
authors.forename: Lida
authors.initials: L
authors.lastname: Zhang
authors.forename: Kaijing
authors.initials: K
authors.lastname: Zuo
authors.forename: Fei
authors.initials: F
authors.lastname: Zhang
authors.forename: Youfang
authors.initials: Y
authors.lastname: Cao
authors.forename: Jiang
authors.initials: J
authors.lastname: Wang
authors.forename: Yidong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xiaofen
authors.initials: X
authors.lastname: Sun
authors.forename: Kexuan
authors.initials: K
authors.lastname: Tang
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D001483:Base Sequence; D017124:Conserved Sequence; D019143:Evolution, Molecular; D018506:Gene Expression Regulation, Plant; D018895:Microsatellite Repeats / Q000235:genetics*; D008969:Molecular Sequence Data; D050436:Regulatory Elements, Transcriptional