硒、砷互作对旱稻砷吸收与代谢的影响机制及相关调控

Many farmlands in some regions around the world are now heavily contaminated by arsenic (As), in particularly in paddy soils in the south central and southwest China. Waterflooding is an important factor affecting As availability in soils and in subsequence As uptake in paddy rice tissues. Upland rice needs less water than paddy rice and often grows in dry farmland, which may efficiently reduce the availability of As in the As-contaminated farmlands and thus lower down As accumulation in rice. However, in some cases , As content in edible parts of crops subjected to As exposure is still higher than the quality standards in terms of As concentration. It is well established that proper dosages of selenium (Se) can be used to reduce the uptake of heavy metals (metalloids, including As) and counteract their toxicity to plants. It is supposed that the combined applications of upland rice and Se might work well to reduce As content in edible parts of crops exposed to high levels of As, and meet the needs of safety production in As-polluted farmland. However, the associated investigations are still scarce. So this study will be conducted to investigate the physiologic and molecular mechanisms on the uptake and metabolism of As in upland rice subjected to different dosages of As and Se, including (1) the mechanisms on the uptake, transport, distribution and species transformation of As and Se;(2) the responses of antioxidative systems involving enzymes and non-enzymes substances to different dosages of As and Se; (3) the responses of As reductase and the regulation of key gene expression. Different adding modes of Se (including adding to soils or foliage spray), different Se species and different variations of upland rice (accumulating and low uptake genotypes) are also considered. All experiments will be performed in pots, and some advanced technologies will be used including SEM/TEM technology, high performance liquid chromatography, high performance liquid chromatography combined with inductively coupled plasma mass spectrometry and real time fluorescence quantitative PCR and reverse transcription. It is hoped that the results of this study will help people understand the mechanisms on the behaviors of As in upland rice subjected to different dosages of As and Se, and provide the theoretical basis and technical support for the safety production of rice in As-polluted farmlands.

农田砷污染是我国中、西南稻作区面临的重要环境问题之一。本项目针对淹水种植下水稻易吸收砷的特点，提出砷污染农田可通过旱稻种植，在显著降低土壤砷活性和生物有效性基础上，利用硒对植物砷吸收、转运的拮抗效应，实现稻米砷的联合阻控和安全生产。迄今，关于硒影响旱稻砷吸收与代谢的研究鲜见报道。项目以砷高、低吸收基因型旱稻为材料，通过土壤盆栽试验，运用透射扫描电镜、液相色谱、HPLC-ICP-MS、实时荧光定量PCR及反转录等技术，在不同砷处理土壤浓度下、以及叶面喷施硒和土壤添加硒两种方式下，研究旱稻体内砷、硒的吸收、转运、分布及形态转化特征，旱稻酶和非酶防御系统的生理响应，旱稻地上部还原酶活性和关键基因表达调控，探讨不同浓度、不同形态硒、砷互作下，旱稻砷吸收与代谢的响应特征及生理与分子机制。研究结果可丰富稻作砷污染相关理论，并为砷污染农田稻米安全生产提供理论依据和技术支持。

农田砷污染是我国中、西南稻作区面临的重要环境问题之一。本项目在非淹水种植降低土壤砷活性和生物有效性基础上，利用硒对植物砷吸收、转运的拮抗效应，实现稻米砷的联合阻控和安全生产。项目采取盆栽试验，以砷高、低吸收基因型旱稻为材料，在不同砷处理土壤浓度下、以及叶面和土壤添加硒两种方式下，研究旱稻体内砷、硒的吸收、转运、分布及形态转化特征，旱稻酶和非酶防御系统的生理响应，旱稻地上部还原酶活性和关键基因表达调控等。主要结论如下：.1. 砷胁迫下旱稻生长受到抑制，且随砷污染程度加深，孕穗期生物量下降了54.72%~92.41%，株高降低了19.36%~48.97%，根施和叶施亚硒酸钠都显著促进了砷胁迫下旱稻的生长，品种V1生物量升高了1.43%~122.96%，品种V2生物量升高了6.2%~59.81%。.2. 全生育期旱种时，品种V1的根、茎、叶、精米、糙米砷含量均小于品种V2；随着土壤砷含量的增加，旱稻各器官砷含量都有显著增加；外施硒酸钠和亚硒酸钠都在不同程度上降低了砷胁迫下旱稻各器官砷含量。.3. 外施亚硒酸钠对砷胁迫下旱稻孕穗期As含量及各器官之间的转运系数影响较大，根施高浓度亚硒酸钠（5.0mg•kg-1）能显著增加旱稻根系As含量（12.71%~55.69%），同时降低其茎、叶As含量，对品种V1茎、叶As含量的降幅分别为16.25~32.09%和15.12%~43.13%，对品种V2茎、叶As含量的降幅为7.32%~29.13%和9.47%~43.27%，其中叶施亚硒酸钠的效果明显优于根施。.4. 旱稻孕穗期的各器官As或Se含量都达到了极显著正相关水平。旱稻孕穗期各器官As含量和Se含量相互之间呈现负相关，其中品种V1茎As含量和根Se含量的相关系数为-0.37，呈显著负相关（P＜0.05）。.5. Se在As胁迫下显著降低了叶MDA含量，V1在不同As胁迫下，Se显著提高了抗氧化酶(SOD、POD和CAT)活性，而V2在As胁迫增强下，Se对抗氧化酶活性先促进后抑制。Se能有效缓解旱稻As胁迫，低(V1)、高(V2) As吸收品种的差异与机制，主要体现在V2对As的吸收与转运远高于V1，以及V2体内的MDA含量、POD和CAT活性远高于V1。.研究结果可丰富稻作砷污染相关理论，并为砷污染农田稻米安全生产提供理论依据和技术支持。