title: The large-scale investigation of gene expression in Leymus chinensis stigmas provides a valuable resource for understanding the mechanisms of poaceae self-incompatibility.
abstract: BACKGROUND
  Many Poaceae species show a gametophytic self-incompatibility (GSI) system, which is controlled by at least two independent and multiallelic loci, S and Z. Until currently, the gene products for S and Z were unknown. Grass SI plant stigmas discriminate between pollen grains that land on its surface and support compatible pollen tube growth and penetration into the stigma, whereas recognizing incompatible pollen and thus inhibiting pollination behaviors. Leymus chinensis (Trin.) Tzvel. (sheepgrass) is a Poaceae SI species. A comprehensive analysis of sheepgrass stigma transcriptome may provide valuable information for understanding the mechanism of pollen-stigma interactions and grass SI.
  
  
  RESULTS
  The transcript abundance profiles of mature stigmas, mature ovaries and leaves were examined using high-throughput next generation sequencing technology. A comparative transcriptomic analysis of these tissues identified 1,025 specifically or preferentially expressed genes in sheepgrass stigmas. These genes contained a significant proportion of genes predicted to function in cell-cell communication and signal transduction. We identified 111 putative transcription factors (TFs) genes and the most abundant groups were MYB, C2H2, C3H, FAR1, MADS. Comparative analysis of the sheepgrass, rice and Arabidopsis stigma-specific or preferential datasets showed broad similarities and some differences in the proportion of genes in the Gene Ontology (GO) functional categories. Potential SI candidate genes identified in other grasses were also detected in the sheepgrass stigma-specific or preferential dataset. Quantitative real-time PCR experiments validated the expression pattern of stigma preferential genes including homologous grass SI candidate genes.
  
  
  CONCLUSIONS
  This study represents the first large-scale investigation of gene expression in the stigmas of an SI grass species. We uncovered many notable genes that are potentially involved in pollen-stigma interactions and SI mechanisms, including genes encoding receptor-like protein kinases (RLK), CBL (calcineurin B-like proteins) interacting protein kinases, calcium-dependent protein kinase, expansins, pectinesterase, peroxidases and various transcription factors. The availability of a pool of stigma-specific or preferential genes for L. chinensis offers an opportunity to elucidate the mechanisms of SI in Poaceae.
authors.affiliation: Key Laboratory of Plant Resources, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Xiangshan, Beijing 100093, China. qyzhou@ibcas.ac.cn.
authors.forename: Qingyuan
authors.initials: Q
authors.lastname: Zhou
authors.forename: Junting
authors.initials: J
authors.lastname: Jia
authors.forename: Xing
authors.initials: X
authors.lastname: Huang
authors.forename: Xueqing
authors.initials: X
authors.lastname: Yan
authors.forename: Liqin
authors.initials: L
authors.lastname: Cheng
authors.forename: Shuangyan
authors.initials: S
authors.lastname: Chen
authors.forename: Xiaoxia
authors.initials: X
authors.lastname: Li
authors.forename: Xianjun
authors.initials: X
authors.lastname: Peng
authors.forename: Gongshe
authors.initials: G
authors.lastname: Liu
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D002450:Cell Communication / Q000235:genetics; D020451:Contig Mapping; D035264:Flowers / Q000235:genetics / Q000378:metabolism; D017343:Genes, Plant; D059014:High-Throughput Nucleotide Sequencing; D012275:Oryza / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D006109:Poaceae / Q000235:genetics* / Q000378:metabolism; D011058:Pollen / Q000235:genetics / Q000378:metabolism; D017423:Sequence Analysis, RNA; D015398:Signal Transduction / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D059467:Transcriptome
chemical_list: D010940:Plant Proteins; D014157:Transcription Factors