Expression profiling of grass-clump dwarf in synthetic hexaploids from triploid hybrids crossed between tetraploid wheat and Aegilops tauschii

We have employed whole genome microarray expression profiling as a discovery platform to identify genes to alter the transcript accumulation levels in grass-clump dwarf lines, which are synthetic hexaploid lines from triploid hybrids crossed between tetraploid wheat (Triticum turgidum ssp. durum cv. Langdon or T. turgidum ssp. carthlicum) and diploid wheat progenitor Aegilops tauschii (KU2025). No up-regulation of defense-related genes was observed under the normal temperature, and down-regulation of wheat APETALA1-like MADS-box genes, considered to act as flowering promoters, was found in the grass-clump dwarf lines. Together with small RNA sequencing analysis of the grass-clump dwarf line, unusual expression of the miR156/SPLs module could explain the grass-clump dwarf phenotype. Expression patterns were compared between the three synthetic hexaploid lines showing the wild-type phenotype (as a reference) and grass-clump dwarf. Total RNA samples were isolated from crown tissues of the plants grown at 24°C under long day (18-h light and 6-h dark) condition for 8 weeks. Two independent experiments were conducted in each exprement.

本研究采用全基因组微阵列表达谱（whole genome microarray expression profiling）作为基因发掘平台，旨在鉴定可改变丛生矮化株系（grass-clump dwarf lines）转录本积累水平的基因。该类株系为四倍体小麦（Triticum turgidum ssp. durum cv. Langdon或T. turgidum ssp. carthlicum）与二倍体小麦祖先种节节麦（Aegilops tauschii，编号KU2025）杂交得到的三倍体杂种所创制的人工合成六倍体株系（synthetic hexaploid lines）。正常培养条件下，未检测到防御相关基因的上调表达；而在丛生矮化株系中，被证实可作为开花促进因子的小麦APETALA1同源MADS-box基因呈现下调表达。结合对该丛生矮化株系的小RNA测序（small RNA sequencing）分析，miR156/SPLs调控模块的异常表达可解释该株系的丛生矮化表型。本研究以3个表现为野生型表型的人工合成六倍体株系作为参照，与丛生矮化株系进行表达模式比较。实验材料为在24℃、长日照（18小时光照/6小时黑暗）条件下培养8周的植株冠部组织，从中提取总RNA（total RNA）样本。每个实验均独立重复两次。