一种Cd高积累蔬菜品种分子标识新方法研究

It was found that there were two SNP (Single nucleotide polymorphism) markers that could be used to identify high-Cd cultivars in PCS1 gene of Chinese flowering cabbage (Brassica parachinensis). The bases in the two locus were different between the high-Cd cultivars and other cultivars. In the high-Cd cultivars, the base located at the locus of 71 nt was G (guanine), but it was A (adenine) in other cultivars. The base at the locus of 394 nt was A in the high-Cd cultivars, but it was G in others. Because the PCS1 gene exists much commonly in plant species, including many vegetable crops, and the identified SNPs locate within exon region which is much stable, it is expected that a molecular biological method for rapid identifying high-Cd cultivars among vegetable crops could be established by using SNP marker technology. Therefore, This study will contribute to develop new biomarker method to prevent heavy metal pollution of crop products against soil contaminations. Main contents of the study include: (1) to investigate the consistency of the target SNPs in high-Cd cultivars among different vegetable crops with different genetic relationships; (2) to prove the changes in expression of gene PCS1 and Cd accumulation in shoot of the crops caused by the target SNPs; (3) to optimize the methods for the SNP examination and identification at earlier developing stage of plant.

课题组在菜心镉积累典型品种的茎叶中发现了在一个植物络合素合成酶基因（BpPCS1）的保守片断中有两个位点的碱基变异具有镉高积累标识功能。该两个位点的碱基在镉高积累品种中与非高积累品种相比有明显差异，其中一个在71nt处的碱基变异表现为镉高积累品种中均为G，非高积累品种中均为A；另一个在394nt处的碱基变异则表现为镉高积累品种均为A，非高积累品种中则均为G。由于该基因普遍存在于植物体内，在多种蔬菜中均有发现，变异所处基因片段十分保守，且属于外显子。因此，利用这种碱基变异，有希望建立一种针对蔬菜镉高积累品种的分子识别技术，对于发展镉污染的生物标识新方法，降低土壤源重金属进入食物链的风险有重要意义。主要研究内容包括：1）具有不同亲缘关系的农作物中镉高积累品种相关碱基变异的一致性研究；2）对象碱基变异对PCS1基因表达及茎叶镉积累的影响；3）各早期发育阶段相关碱基变异的检测和识别方法优化。

我国农田土壤重金属污染已成为不容忽视的农业环境问题，控制农作物的重金属污染已经成为十分紧迫的任务。尽管人们已开始关注重金属低量积累农作物品种，但对于这些品种的了解，尤其是其重金属低量积累机理仍知之甚少。课题组在菜心镉积累典型品种的茎叶中发现了在一个植物络合素合成酶基因（BpPCS1）的保守片断中有两个位点的碱基变异具有镉高积累标识功能。该两个位点的碱基在镉高积累品种中与非高积累品种相比有明显差异，其中一个在71nt处的碱基变异表现为镉高积累品种中均为G，非高积累品种中均为A；另一个在394nt处的碱基变异则表现为镉高积累品种均为A，非高积累品种中则均为G。课题组希望利用这种碱基变异，建立一种针对蔬菜镉高积累品种的分子识别技术，这对于发展镉污染的生物标识新方法，降低土壤源重金属进入食物链的风险有重要意义。但课题组研究中发现PCS1基因可能不是导致小白菜和蕹菜镉积累品种间差异的关键基因，并且菜心PCS1基因保守片段的两个碱基变异在菜心、小白菜、芥菜、西洋菜和蕹菜中不具有一致性，其作为蔬菜中高镉积累品种分子标识物并不具有可行性和普适性。因此在后续研究中对蕹菜和菜心镉高低积累品种进行了RNA-Seq和miRNA测序研究，对小白菜开展了RNA-Seq研究，筛选了一批蔬菜镉积累相关基因，探讨了蔬菜镉积累品种间差异的分子机理，研究结果可为发展定向培育镉低量积累品种的育种技术奠定理论基础，有利于保障食品安全以及在保障正常的农业生产的同时有效便捷地预防土壤源重金属的危害。