Su Qiufang, Zheng Xiaodong, Tian Yike, Wang Caihong
College of Horticulture, Qingdao Agricultural University, Qingdao, China.
Qingdao Key Laboratory of Genetic Improvement and Breeding in Horticulture Plants, Qingdao Agricultural University, Qingdao, China.
Front Plant Sci. 2020 Feb 6;11:38. doi: 10.3389/fpls.2020.00038. eCollection 2020.
Brassinolide (BL) mediates various physiological processes and improves plant tolerance to abiotic stresses. However, the effects and mechanism of exogenous BL on the salt tolerance of apple seedlings remain unclear. Herein, we investigated the role of BL in the salt stress response of Rehd., a widely grown apple rootstock. Salt-stressed apple seedlings showed significant decline in chlorophyll content and photosynthetic rate, and the application of 0.2 mg/L exogenous BL alleviated salt stress and maintained photosynthetic capacity. Exogenous BL application can strengthen the activities of superoxide dismutase and catalase and thereby eliminates reactive oxygen species (ROS) production induced by salt stress and promote the accumulation of proline and soluble sugar, thus maintaining osmotic balance. Furthermore, exogenous BL application decreased Na accumulation and increased K content in shoots and roots under salt stress by regulating the expression levels of Na(K)/H antiporter genes (). MhBZR1 and MhBZR2, which are the key transcription factors in the BR signal transduction pathway, can directly bind to the promoter of and , respectively, and inhibit their expression. Our findings would provide a theoretical basis for analyzing the mechanism of exogenous BL application on the salt tolerance of apples.
油菜素内酯（BL）介导多种生理过程并提高植物对非生物胁迫的耐受性。然而，外源BL对苹果幼苗耐盐性的影响及机制尚不清楚。在此，我们研究了BL在广泛种植的苹果砧木平邑甜茶（Malus hupehensis Rehd.）盐胁迫响应中的作用。盐胁迫下的苹果幼苗叶绿素含量和光合速率显著下降，施用0.2 mg/L外源BL可缓解盐胁迫并维持光合能力。外源BL处理可增强超氧化物歧化酶和过氧化氢酶的活性，从而消除盐胁迫诱导的活性氧（ROS）产生，并促进脯氨酸和可溶性糖的积累，从而维持渗透平衡。此外，外源BL处理通过调节Na（K）/H逆向转运蛋白基因（MhNHX1和MhHKT1;1）的表达水平，降低了盐胁迫下地上部和根部的Na积累并增加了K含量。MhBZR1和MhBZR2是油菜素内酯信号转导途径中的关键转录因子，它们可以分别直接结合MhNHX1和MhHKT1;1的启动子并抑制它们的表达。我们的研究结果将为分析外源BL提高苹果耐盐性的机制提供理论依据。
