Zeng Fangqin, Biligetu Bill, Coulman Bruce, Schellenberg Michael P, Fu Yong-Bi
Department of Plant Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Swift Current Research and Development Center, Agriculture and Agri-Food Canada, Swift Current, Saskatchewan, Canada.
PLoS One. 2017 May 22;12(5):e0177417. doi: 10.1371/journal.pone.0177417. eCollection 2017.
Crested wheatgrass [Agropyron cristatum L. (Gaertn.)] is widely used for early spring grazing in western Canada and the development of late maturing cultivars which maintain forage quality for a longer period is desired. However, it is difficult to manipulate the timing of floral transition, as little is known about molecular mechanism of plant maturity in this species. In this study, RNA-Seq and differential gene expression analysis were performed to investigate gene expression for floral initiation and development in crested wheatgrass. Three cDNA libraries were generated and sequenced to represent three successive growth stages by sampling leaves at the stem elongation stage, spikes at boot and anthesis stages. The sequencing generated 25,568,846; 25,144,688 and 25,714,194 qualified Illumina reads for the three successive stages, respectively. De novo assembly of all the reads generated 311,671 transcripts with a mean length of 487 bp, and 152,849 genes with an average sequence length of 669 bp. A total of 48,574 (31.8%) and 105,222 (68.8%) genes were annotated in the Swiss-Prot and NCBI non-redundant (nr) protein databases, respectively. Based on the Kyoto Encyclopedia of Genes and Genome (KEGG) pathway database, 9,723 annotated sequences were mapped onto 298 pathways, including plant circadian clock pathway. Specifically, 113 flowering time-associated genes, 123 MADS-box genes and 22 CONSTANS-LIKE (COL) genes were identified. A COL homolog DN52048-c0-g4 which was clustered with the flowering time genes AtCO and OsHd1 in Arabidopsis (Arabidopsis thaliana L.) and rice (Oryza sativa L.), respectively, showed specific expression in leaves and could be a CONSTANS (CO) candidate gene. Taken together, this study has generated a new set of genomic resources for identifying and characterizing genes and pathways involved in floral transition and development in crested wheatgrass. These findings are significant for further understanding of the molecular basis for late maturity in this grass species.
扁穗冰草[Agropyron cristatum L. (Gaertn.)]在加拿大西部被广泛用于早春放牧，因此人们期望培育出晚熟品种，以在更长时间内保持饲草质量。然而，由于对该物种植物成熟的分子机制了解甚少，所以很难控制花期转换的时间。在本研究中，进行了RNA测序和差异基因表达分析，以研究扁穗冰草中花起始和发育的基因表达。通过在茎伸长阶段采集叶片、孕穗期和开花期采集穗子，构建了三个cDNA文库并进行测序，以代表三个连续的生长阶段。三个连续阶段分别产生了25,568,846、25,144,688和25,714,194条合格的Illumina reads。对所有reads进行从头组装，产生了311,671条转录本，平均长度为487 bp，以及152,849个基因，平均序列长度为669 bp。分别有48,574个(31.8%)和105,222个(68.8%)基因在Swiss-Prot和NCBI非冗余(nr)蛋白质数据库中得到注释。基于京都基因与基因组百科全书(KEGG)通路数据库，9,723条注释序列被映射到298条通路，包括植物昼夜节律钟通路。具体而言，鉴定出113个开花时间相关基因、123个MADS-box基因和22个CONSTANS-LIKE (COL)基因。一个COL同源基因DN52048-c0-g4分别与拟南芥(Arabidopsis thaliana L.)和水稻(Oryza sativa L.)中的开花时间基因AtCO和OsHd1聚类，在叶片中表现出特异性表达，可能是一个CONSTANS (CO)候选基因。综上所述，本研究产生了一组新的基因组资源，用于鉴定和表征参与扁穗冰草花期转换和发育的基因及通路。这些发现对于进一步了解该草种晚熟的分子基础具有重要意义。
