Abstract:

Developing efficient foliar inhibitors and elucidating their mechanisms of action are of great significance for promoting the application of foliar spraying technology in the remediation of arsenic (As)-contaminated paddy fields. In this study, the rice cultivar Huanghuazhan was used as the test material to investigate the effects of S-allyl-L-cysteine (SAC) on As accumulation in different rice tissues via pot experiments. Furthermore, the regulatory effects of SAC treatment on grain nitrogen (N), phosphorus (P), and potassium (K) contents, the expression levels of related genes, and leaf hydrogen sulfide (H₂S) content were analyzed to reveal the physiological and molecular mechanisms by which SAC reduces As content in rice. The results showed that spraying 0.2 mmol/L SAC significantly decreased As content in roots, stems, and grains by 10.1%, 16.1%, and 18.8%, respectively, compared to the untreated control(CK). However, it increased As content in leaves by 11.5%. Additionally, spraying 0.2 mmol/L SAC induced the downregulation of OsLsi1 and OsLsi2 gene expression in leaves and the top first node by 20.0% and 18.2%, respectively, while upregulating the expression of OsABCC1, OsPCS1, OsPAL6 and OsAIM1 by 63.2%, 34.6%, 69.2%, and 76.1%, respectively. It also significantly enhanced the H₂S fluorescence signal in leaves. Correlation analysis revealed a significant negative correlation between SAC concentration and grain As content, and a significant positive correlation with grain N content. Compared with SAC treatment alone, combined spraying of SAC and hypotaurine (HT), significantly increased the As content in grains; reversed the expression of related genes, and weakened the H₂S fluorescence intensity in leaves. In conclusion, SAC reduces As accumulation in rice by activating endogenous H₂S signaling and regulating the expression of As-related transport and detoxification genes, demonstrating good potential for application in the remediation of As-contaminated soils.

Key words: rice, arsenic, S-allyl-L-cysteine, hydrogen sulfide, gene expression

摘要：

开发高效叶面阻控剂并阐明其作用机理，对推动叶面喷施技术在砷（As）污染稻田治理中的应用具有重要意义。本研究以水稻品种黄华占为供试材料，通过盆栽试验探究S-烯丙基-L-半胱氨酸（SAC）对水稻不同部位As积累的影响，进一步分析SAC处理对水稻籽粒氮（N）、磷（P）、钾（K）含量、相关基因表达水平及叶片硫化氢（H₂S）含量的调控作用，旨在揭示SAC降低水稻As含量的生理与分子机制。结果表明，喷施0.2 mmol/L SAC可显著降低水稻根、茎和籽粒中的As含量，与未喷施处理（CK）相比分别降低10.1%、16.1%和18.8%；但增加了叶片As含量，较未喷施处理增加11.5%。此外，喷施0.2 mmol/L SAC可诱导叶片和顶端第1节中OsLsi1和OsLsi2基因表达分别下调20.0%和18.2%，OsABCC1、OsPCS1、OsPAL6和OsAIM1基因表达分别上调63.2%、34.6%、69.2%和76.1%，并显著增强叶片H₂S荧光信号。相关分析显示，SAC浓度与籽粒As含量呈显著负相关，与籽粒N含量呈显著正相关。喷施SAC+亚牛磺酸（HT）处理籽粒As含量较单独喷施SAC处理显著上升，相关基因表达出现回调，叶片H₂S荧光强度相应减弱。综上所述，SAC通过激活水稻内源H₂S信号，调控As相关转运与解毒基因的表达，从而降低水稻As积累，显示出在As污染土壤修复中的良好应用潜力。

关键词: 水稻, 砷, S-烯丙基-L-半胱氨酸, 硫化氢, 基因表达