title: Identification and comparative analysis of drought-associated microRNAs in two cowpea genotypes.
abstract: BACKGROUND
  Cowpea (Vigna unguiculata) is an important crop in arid and semi-arid regions and is a good model for studying drought tolerance. MicroRNAs (miRNAs) are known to play critical roles in plant stress responses, but drought-associated miRNAs have not been identified in cowpea. In addition, it is not understood how miRNAs might contribute to different capacities of drought tolerance in different cowpea genotypes.
  
  
  RESULTS
  We generated deep sequencing small RNA reads from two cowpea genotypes (CB46, drought-sensitive, and IT93K503-1, drought-tolerant) that grew under well-watered and drought stress conditions. We mapped small RNA reads to cowpea genomic sequences and identified 157 miRNA genes that belong to 89 families. Among 44 drought-associated miRNAs, 30 were upregulated in drought condition and 14 were downregulated. Although miRNA expression was in general consistent in two genotypes, we found that nine miRNAs were predominantly or exclusively expressed in one of the two genotypes and that 11 miRNAs were drought-regulated in only one genotype, but not the other.
  
  
  CONCLUSIONS
  These results suggest that miRNAs may play important roles in drought tolerance in cowpea and may be a key factor in determining the level of drought tolerance in different cowpea genotypes.
authors.affiliation: Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA.
authors.forename: Blanca E
authors.initials: BE
authors.lastname: Barrera-Figueroa
authors.forename: Lei
authors.initials: L
authors.lastname: Gao
authors.forename: Ndeye N
authors.initials: NN
authors.lastname: Diop
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Wu
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Ehlers
authors.forename: Philip A
authors.initials: PA
authors.lastname: Roberts
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Close
authors.forename: Jian-Kang
authors.initials: JK
authors.lastname: Zhu
authors.forename: Renyi
authors.initials: R
authors.lastname: Liu
mesh_terms: D055864:Droughts; D007887:Fabaceae / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D005838:Genotype; D035683:MicroRNAs / Q000235:genetics*; D018749:RNA, Plant / Q000235:genetics*; D017423:Sequence Analysis, RNA
chemical_list: D035683:MicroRNAs; D018749:RNA, Plant