Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, 739-8528, Japan; Department of Botany and Microbiology, Faculty of Science, Minia University, El-Minia 61519, Egypt.
Graduate School for International Development and Cooperation, Hiroshima University, Higashi-Hiroshima, 739-8529, Japan.
Plant Physiol Biochem. 2018 Sep;130:94-104. doi: 10.1016/j.plaphy.2018.06.036. Epub 2018 Jun 30.
Soil salinity is a limiting factor in rice production. Since flavonoids present in most plant tissues play multiple roles in plant-environment interactions, in this study, we focused on the contribution of flavone aglycone (Apigenin) to the adaptation of salinity-sensitive rice cultivar 'Koshihikari,' to salinity stress, for the first time. Rice seeds were soaked in Apigenin solution (10 ppm) for 24 h, then air-dried and grown hydroponically under 50 mM NaCl for 14 days. Apigenin pretreatment improved the growth of rice seedlings by enhancing shoot elongation and dry mass accumulation under both unstressed and NaCl-stress conditions, compared with that in the non-pretreated seedlings. Apigenin pretreatment significantly reduced Na accumulation in the salinity-stressed seedlings, and helped to maintain a lower Na/K ratio in all plant organs, compared with that in the non-pretreated seedlings, possibly by regulating the expression of some important Na transporter-encoding genes (OsHKT2;1, OsCNGC1, OsSOS1). Higher levels of lipid peroxidation and hydrogen peroxide (HO) concentrations were observed in the shoots of the salinity-stressed seedlings; however, lower levels of lipid peroxidation and HO concentration were detected in the Apigenin-treated seedlings. Apigenin pretreatment was associated with the induction of the rice antioxidant defense system represented by the induced activities of the antioxidant enzymes Catalase (CAT) and Ascorbate peroxidase (APX) in the roots, as well as by increased accumulation of the non-enzymatic antioxidants carotenoids and flavonoids in the shoots, relative to that in the untreated seedlings, under salinity stress conditions. Together, these results suggest that Apigenin pretreatment can alleviate the damaging effects of salinity on rice seedlings, presumably by regulating selective ion uptake by the roots and translocation to the shoots, thereby maintaining higher K/Na ratios critical for normal plant growth under salinity stress, and by triggering the induction of the antioxidant defense system.
土壤盐度是水稻生产的一个限制因素。由于大多数植物组织中存在的类黄酮在植物与环境相互作用中发挥多种作用，因此本研究首次关注了黄酮苷元（芹菜素）对盐敏感水稻品种“越光”适应盐胁迫的贡献。将水稻种子浸泡在芹菜素溶液（10ppm）中 24 小时，然后风干，在 50mM NaCl 下水培 14 天。与未经预处理的幼苗相比，芹菜素预处理通过增强未胁迫和 NaCl 胁迫条件下的茎伸长和干物质积累，促进了水稻幼苗的生长。与未经预处理的幼苗相比，芹菜素预处理显著降低了盐胁迫幼苗中 Na 的积累，并有助于维持所有植物器官中较低的 Na/K 比，可能是通过调节一些重要的 Na 转运蛋白编码基因（OsHKT2;1、OsCNGC1、OsSOS1）的表达。在盐胁迫的幼苗中观察到更高水平的脂质过氧化和过氧化氢（HO）浓度；然而，在经芹菜素处理的幼苗中，脂质过氧化和 HO 浓度较低。与未经处理的幼苗相比，在盐胁迫条件下，芹菜素预处理与诱导的水稻抗氧化防御系统相关，该系统表现为根系中抗氧化酶过氧化氢酶（CAT）和抗坏血酸过氧化物酶（APX）的活性增强，以及茎中非酶抗氧化剂类胡萝卜素和类黄酮的积累增加。总之，这些结果表明，芹菜素预处理可以减轻盐胁迫对水稻幼苗的破坏作用，可能是通过调节根系的选择性离子吸收和向地上部的转运，从而在盐胁迫下维持对正常植物生长至关重要的更高的 K/Na 比，并触发抗氧化防御系统的诱导。
