Table_1_TRA1: A Locus Responsible for Controlling Agrobacterium-Mediated Transformability in Barley.docx

In barley (Hordeum vulgare L.), Agrobacterium-mediated transformation efficiency is highly dependent on genotype with very few cultivars being amenable to transformation. Golden Promise is the cultivar most widely used for barley transformation and developing embryos are the most common donor tissue. We tested whether barley mutants with abnormally large embryos were more or less amenable to transformation and discovered that mutant M1460 had a transformation efficiency similar to that of Golden Promise. The large-embryo phenotype of M1460 is due to mutation at the LYS3 locus. There are three other barley lines with independent mutations at the same LYS3 locus, and one of these, Risø1508 has an identical missense mutation to that in M1460. However, none of the lys3 mutants except M1460 were transformable showing that the locus responsible for transformation efficiency, TRA1, was not LYS3 but another locus unique to M1460. To identify TRA1, we generated a segregating population by crossing M1460 to the cultivar Optic, which is recalcitrant to transformation. After four rounds of backcrossing to Optic, plants were genotyped and their progeny were tested for transformability. Some of the progeny lines were transformable at high efficiencies similar to those seen for the parent M1460 and some were not transformable, like Optic. A region on chromosome 2H inherited from M1460 is present in transformable lines only. We propose that one of the 225 genes in this region is TRA1.

在大麦（Hordeum vulgare L.）中，农杆菌介导的转化（Agrobacterium-mediated transformation）效率高度依赖于基因型，仅有极少数栽培品种可实现转化。金承诺（Golden Promise）是目前大麦转化研究中应用最广泛的栽培品种，而发育胚是最常用的转化供体组织。本研究探究了胚异常偏大的大麦突变体的转化可行性，发现突变体M1460的转化效率与金承诺（Golden Promise）相当。M1460的大胚表型源于LYS3基因座（LYS3 locus）的突变。另有3个大麦品系在同一LYS3基因座（LYS3 locus）上存在独立突变，其中品系Risø1508与M1460携带相同的错义突变。但除M1460外，其余lys3突变体均无法实现转化，这表明调控转化效率的基因座TRA1并非LYS3，而是M1460特有的另一基因座。为了定位克隆TRA1，本研究将M1460与转化难持性品种Optic杂交，构建了分离群体。对杂交后代进行4轮回交至Optic后，对植株进行基因分型，并对其后代的转化能力进行检测。部分后代株系可实现高效转化，其效率与亲本M1460相当，而另一部分则如Optic一样无法转化。仅在可转化株系中，存在来自M1460的2H染色体区段。本研究推测该区段内的225个基因中，某一个即为TRA1。