木薯种质资源中醇腈裂解酶基因12G132600编码区终止突变及频率的研究

Premature Mutation Frequencies in Coding Region of Gene 12G132600 Encoding Alpha-hydroxy Nitrile Lyase in Cassava Germplasms

木薯是重要的粮食作物,但块根中含有的氰苷及其产生的氢氰酸严重影响木薯的食用品质,增加加工成本。α-醇腈裂解酶(alpha-hydroxynitrilelyase,HNL)是植物催化醇腈裂解产生氢氰酸的关键酶。重测序数据显示,‘华南8号’木薯品种中HNL编码基因家族的一个成员12G132600在编码区内部发生了终止突变,导致基因编码区变短。本研究对国内外251份木薯种质资源的重测序结果进行分析,共发现60份材料醇腈裂解酶基因12G132600存在相同的终止突变,该60份材料全部是终止突变与非终止突变的杂合基因型,且全部为栽培类型木薯。说明该突变是木薯由野生型驯化为栽培型以后发生的。通过对木薯品种‘华南9号’该基因的克隆测序以及与已发表的木薯品种‘TME3’基因组序列的比对分析,证实了该突变在木薯品种中真实存在。

Cassava is an important food crop in the world.The presence of high-level cyanogenic glucosides and HCN produced poses a major nutritive drawback and means a higher labor costs to remove these toxic substances.Cyanogensis is an important protective mechanism for plant to avoid grazing by animals.Alpha-hydroxy nitrile lyase(HNL)plays a key role in cyanogensis reaction.We found that there was a premature termination mutation in the coding sequence of HNL gene of cassava variety SC8,which would result in short length in protein encoded and could affect the function of the protein.These researches would give useful information about the role of the point mutation and provide new ideals for selecting cassava accessions with low-content hydrocyanic acid in molecular breeding.Firstly we surveyed the resequencing data of 251 cassava varieties from all around the world to characterize the same mutation site in HNL gene and found that there were sixty accessions belonging to cultivated cassava harboring the same mutation as SC8,indicting the premature mutation occurred during or after cassava domestication.We cloned and sequenced the orthologous genes of 12 G132600 in SC9 by PCR and compared the corresponding sequence of TME3 from the genome assembly.The results further strengthened the evidence of this premature mutation in cassava varieties.