National Institute of Plant Genome Research (NIPGR), New Delhi, India.
Plant Biotechnol J. 2013 Sep;11(7):855-66. doi: 10.1111/pbi.12078. Epub 2013 May 31.
Brassica juncea (Indian mustard), a globally important oilseed crop, contains relatively high amount of seed glucosinolates ranging from 80 to 120 μmol/g dry weight (DW). One of the major breeding objectives in oilseed Brassicas is to improve the seed-meal quality through the development of low-seed-glucosinolate lines (<30 μmol/g DW), as high amounts of certain seed glucosinolates are known to be anti-nutritional and reduce the meal palatability. Here, we report the development of transgenic B. juncea lines having seed glucosinolates as low as 11.26 μmol/g DW, through RNAi-based targeted suppression of BjMYB28, a R2R3-MYB transcription factor family gene involved in aliphatic glucosinolate biosynthesis. Targeted silencing of BjMYB28 homologs provided significant reduction in the anti-nutritional aliphatic glucosinolates fractions, without altering the desirable nonaliphatic glucosinolate pool, both in leaves and seeds of transgenic plants. Molecular characterization of single-copy, low glucosinolate homozygous lines confirmed significant down-regulation of BjMYB28 homologs vis-à-vis enhanced accumulation of BjMYB28-specific siRNA pool. Consequently, these low glucosinolate lines also showed significant suppression of genes involved in aliphatic glucosinolate biosynthesis. The low glucosinolate trait was stable in subsequent generations of the transgenic lines with no visible off-target effects on plant growth and development. Various seed quality parameters including fatty acid composition, oil content, protein content and seed weight of the low glucosinolate lines also remained unaltered, when tested under containment conditions in the field. Our results indicate that targeted silencing of a key glucosinolate transcriptional regulator MYB28 has huge potential for reducing the glucosinolates content and improving the seed-meal quality of oilseed Brassica crops.
芥菜型油菜（芥菜）是一种全球重要的油料作物，其种子中的硫代葡萄糖苷含量相对较高，范围在 80 至 120μmol/g 干重（DW）。在油料芥菜中，主要的育种目标之一是通过开发低硫代葡萄糖苷含量的品系（<30μmol/g DW）来改善种子粉的质量，因为已知高含量的某些种子硫代葡萄糖苷具有抗营养性，并降低了粉的适口性。在这里，我们通过 RNAi 靶向抑制参与脂肪族硫代葡萄糖苷生物合成的 R2R3-MYB 转录因子家族基因 BjMYB28，报道了种子硫代葡萄糖苷低至 11.26μmol/g DW 的转基因芥菜型油菜品系的开发。BjMYB28 同源物的靶向沉默在转基因植物的叶片和种子中，显著降低了抗营养性的脂肪族硫代葡萄糖苷，而不改变理想的非脂肪族硫代葡萄糖苷库。单拷贝、低硫代葡萄糖苷纯合子系的分子特征证实，BjMYB28 同源物的下调显著增强了 BjMYB28 特异性 siRNA 库的积累。因此，这些低硫代葡萄糖苷系也显示出参与脂肪族硫代葡萄糖苷生物合成的基因的显著抑制。在转基因系的后续世代中，低硫代葡萄糖苷性状是稳定的，对植物生长和发育没有明显的脱靶效应。在田间的封闭条件下进行测试时，低硫代葡萄糖苷系的各种种子质量参数，包括脂肪酸组成、油含量、蛋白质含量和种子重量，也保持不变。我们的结果表明，靶向沉默关键硫代葡萄糖苷转录调节因子 MYB28 具有降低硫代葡萄糖苷含量和改善油料芥菜作物种子粉质量的巨大潜力。
