Hayes Chad M, Burow Gloria B, Brown Patrick J, Thurber Carrie, Xin Zhanguo, Burke John J
USDA-ARS, Plant Stress & Germplasm Development Unit, Cropping Systems Research Lab., Lubbock, TX, 79415.
Dep. of Crop Sciences, Univ. of Illinois, Urbana, IL, 61801.
Plant Genome. 2015 Jul;8(2):eplantgenome2014.09.0048. doi: 10.3835/plantgenome2014.09.0048.
Cyanogenic glucosides are natural compounds found in more than 1000 species of angiosperms that produce HCN and are deemed undesirable for agricultural use. However, these compounds are important components of the primary defensive mechanisms of many plant species. One of the best-studied cyanogenic glucosides is dhurrin [(S)-p-hydroxymandelonitrile-β-D-glucopyranoside], which is produced primarily in sorghum [Sorghum bicolor (L.) Moench]. The biochemical basis for dhurrin metabolism is well established; however, little information is available on its genetic control. Here, we dissect the genetic control of leaf dhurrin content through a genome-wide association study (GWAS) using a panel of 700 diverse converted sorghum lines (conversion panel) previously subjected to pre-breeding and selected for short stature (∼1 m in height) and photoperiod insensitivity. The conversion panel was grown for 2 yr in three environments. Wide variation for leaf dhurrin content was found in the sorghum conversion panel, with the Caudatum group exhibiting the highest dhurrin content and the Guinea group showing the lowest dhurrin content. A GWAS using a mixed linear model revealed significant associations (a false discovery rate [FDR] < 0.05) close to both UGT 185B1 in the canonical biosynthetic gene cluster on chromosome 1 and close to the catabolic dhurrinase loci on chromosome 8. Dhurrin content was associated consistently with biosynthetic genes in the two N-fertilized environments, while dhurrin content was associated with catabolic loci in the environment without supplemental N. These results suggest that genes for both biosynthesis and catabolism are important in determining natural variation for leaf dhurrin in sorghum in different environments.
生氰糖苷是在1000多种被子植物中发现的天然化合物，这些化合物会产生氰化氢，被认为不适用于农业用途。然而，这些化合物是许多植物物种主要防御机制的重要组成部分。研究得最为透彻的生氰糖苷之一是蜀黍苷[（S）-对羟基苯乙腈-β-D-吡喃葡萄糖苷]，它主要在高粱[双色高粱（L.）Moench]中产生。蜀黍苷代谢的生化基础已得到充分确立；然而，关于其遗传控制的信息却很少。在此，我们通过全基因组关联研究（GWAS）剖析叶片蜀黍苷含量的遗传控制，该研究使用了一组700个经过预育种且因植株矮小（高度约1米）和光周期不敏感而被挑选出来的不同高粱品系（转换群体）。该转换群体在三种环境中种植了两年。在高粱转换群体中发现叶片蜀黍苷含量存在广泛变异，其中尾稃组的蜀黍苷含量最高，几内亚组的蜀黍苷含量最低。使用混合线性模型的GWAS揭示了与1号染色体上经典生物合成基因簇中的UGT 185B1以及8号染色体上分解代谢的蜀黍苷酶基因座附近存在显著关联（错误发现率[FDR]<0.05）。在两个施氮肥环境中，蜀黍苷含量始终与生物合成基因相关，而在无补充氮的环境中，蜀黍苷含量与分解代谢基因座相关。这些结果表明，生物合成和分解代谢的基因在决定不同环境下高粱叶片蜀黍苷的自然变异方面都很重要。
