玉米对砷耐受的关键基因ZmPAPR的功能解析

Arsenic contamination of maize kernels affects their food safety. In order to explore the genetic basis of low arsenic enrichment traits in grains, we determined the As content of 256 re-sequencing maize inbred lines by ICP-MS method. Using genome-wide association analysis, we identified a candidate gene related to As enrichment in maize seeds, which is ZmPAPR. This gene encodes 3'-adenosine 5'- Phosphorylated sulphate reductase. ZmPAPR is a key enzyme in the sulfur reduction pathway, and is also the upstream gene of glutathione synthesis pathway. However, there is no report that this gene is involved in regulating maize tolerance and detoxification for As. This project intends to identify correlation between ZmPAPR gene expression level and maize As tolerance ability, to determine the expression pattern and protein localization region of ZmPAPR, to identify key structural variations in natural populations that lead to differences in expression of the gene, and develop molecular markers. This study hopes to elucidate the role of ZmPAPR gene in the As tolerance and detoxification in maize, and provide a theoretical basis for the screening and creation of seeds low-enriched As maize materials.

玉米籽粒砷污染影响其食品安全性。为了探索籽粒低砷富集性状的遗传基础，我们用ICP-MS法测定了256份重测序玉米自交系籽粒中砷含量，采用全基因组关联分析鉴定到与玉米籽粒中砷富集相关候选基因ZmPAPR，该基因编码3’-磷酸腺苷酸5’-磷酸化硫酸还原酶。ZmPAPR基因参与叶片中硫还原，是植物抗逆境胁迫前体谷胱甘肽上游基因，目前没有该基因参与调控玉米对砷耐受和解毒的报道。为了弄清该基因在玉米叶片中对砷的耐受性和解毒相关功能，从而达到减少籽粒砷含量的目的，本项目拟通过对ZmPAPR基因的功能及机理研究，确定ZmPAPR表达量差异与玉米对砷耐受的相关性；明确ZmPAPR的表达模式和蛋白定位区域；鉴定自然群体中导致该基因表达差异从而影响其对砷耐受性的关键结构变异，开发分子标记。本研究希望能阐明ZmPAPR基因参与玉米对砷耐受性和解毒的相关功能，为籽粒低富集砷的玉米材料的筛选和创制提供理论依据。

土壤砷污染成为玉米生产中面临的主要非生物胁迫因素。玉米籽粒中积累砷超标，影响食品安全，威胁着人们的健康。为了探索籽粒砷富集性状的遗传基础，创制籽粒低砷富集材料，我们用ICP-MS法测定了256份重测序玉米自交系籽粒中砷含量，砷含量大概在0.0743-0.2764 mg kg-1,采用全基因组关联分析鉴定到与玉米籽粒中砷富集相关候选基因ZmPAPR，编码3’-磷酸腺苷酸5’-磷酸化硫酸还原酶。ZmPAPR基因参与叶片中硫还原，是植物抗逆境胁迫前体谷胱甘肽上游基因，目前没有该基因参与调控玉米对砷耐受和解毒的报道。用不同浓度的砷处理野生型玉米幼苗，ZmPAPR基因的表达受到砷的诱导。本研究将ZmPAPR敲出后,突变体籽粒砷含量升高。将ZmPAPR在叶片中过量表达，与野生型相比，籽粒中的砷含量降低。对ZmPAPR基因的杂合突变体和过表达叶片RNAseq分析发现，差异基因主要体现在硫代谢的下游基因，主要为谷胱甘肽和几丁质酶相关基因。该基因有可能通过以上两个方面调节玉米植株对砷的耐受和分配。过表达ZmPAPR提高了叶片的氧化还原状态，提高了谷胱甘肽的含量，从而提高对砷的富集能力，将砷更多的富集到液泡中，向籽粒运输的砷降低。该基因在不影响产量和其他农艺性状的情况下，可以减少籽粒中砷的富集，在提高粮食安全性方面具有重要意义。