南湖新聞網訊 植物激素在植物生長發育、抵抗生物和非生物脅迫中發揮著重要的調控作用。近日，華中農業大學植物營養生物學團隊研究揭示了油菜素甾醇（BRs）和茉莉酸（JA）參與植物響應缺硼脅迫的分子調控機制。
油菜素甾醇（brassinosteroids, BRs）是一類多羥基的甾醇類植物激素，因首先從油菜花粉中發現提取而得名，廣泛分布在植物的根、莖、葉片、花、種子和幼嫩的生長組織中，調控植物的生長發育。植物缺硼會嚴重抑制主根的生長，該團隊通過研究分析擬南芥響應缺硼和BR的RNA-seq結果，發現兩者共表達的基因數高達45.9%（圖1c），且這些共表達的基因大部分呈現相反的表達趨勢。與野生型相比，BR的受體突變體bri1-119和bri1-301表現出對低硼脅迫不敏感，而BR信號增強突變體bes1-D對缺硼脅迫則表現出顯著高的抗性（圖1a）。此外，外源添加24-表油菜素內酯（eBL）能顯著緩解根的生長抑制（圖1b），而添加BR合成抑制劑BRZ會加重根生長的抑制，且缺硼減少了BES1的核信號，但在缺硼條件下添加eBL則能增加BES1的核信號。進一步研究發現缺硼通過抑制BR合成基因BR6ox1和BR6ox2的表達而減少了油菜素內酯（BL）的合成（圖1d）。
茉莉酸（JA）是調節植物生長發育、抵御逆境脅迫的一種植物激素。植物營養生物學團隊研究發現缺硼條件下擬南芥地上部和根中積累JA達到正常硼條件下的7.9倍和2.8倍，生長受嚴重抑制，外源添加JA合成抑制劑DIECA則可以緩解缺硼對生長的抑制。團隊進一步鑒定到一個缺硼誘導的乙烯轉錄因子ERF018，通過作用于JA合成基因AOCs的啟動子區域，上調了JA合成基因的表達，使JA合成增多。在茉莉酸氨基酸結合酶JAR1的作用下，增多的JA進一步轉變為有生物活性形式的茉莉酸-異亮氨酸JA-Ile。JA-Ile與受體復合物SCFCOI1結合激活JA下游信號，參與缺硼對擬南芥生長的抑制。同時，研究發現缺硼上調了乙烯（ET）合成基因的表達，使ET積累，并負調主根生長。JA通過抑制jar1-1突變體中乙烯信號轉錄因子EIN3的蛋白水平，從而實現JA與ET協同作用于缺硼對主根生長的抑制。JA并不直接調控硼的吸收轉運，而是通過影響缺硼時根系構型而影響硼的吸收。
上述研究獲得了國家自然科學基金、國家重點研發計劃和中央高校基本科研業務費專項基金資助，團隊成員汪社亮副研究員、王創研究員，丁廣大副教授，蔡紅梅副教授和石磊教授等參與了研究工作。
【英文摘要】
Brassinosteroids （BRs） are pivotal phytohormones involved in dominating root development. Boron （B） is an essential micronutrient for plants, and root growth is rapidly inhibited under B‐deficiency conditions. However, the mechanisms underlying this inhibition are still unclear. Here, we identified BR‐related processes underlying B deficiency at the physiological, genetic, molecular/cell biological and transcriptomic levels and found strong evidence that B deficiency can affect BR biosynthesis and signalling, thereby altering root growth. RNA sequencing analysis revealed strong co‐regulation between BR‐regulated genes and B deficiency‐responsive genes. We found that the BR receptor mutants bri1‐119 and bri1‐301 were more insensitive to decreased B supply, and the gain‐of function mutants bes1‐D and pBZR1‐bzr1‐D lines exhibited insensitivity to low‐B stress. Under B‐deficiency conditions, exogenous 24‐epibrassinolide （eBL） rescued the inhibition of root growth, and application of the BR biosynthesis inhibitor BRZ exacerbated this inhibitory effect. The nuclear‐localized signal of BES1 was reduced under low‐B conditions compared with B‐sufficiency conditions. We further found that B deficiency hindered the accumulation of brassinolide （BL） to downregulate BR signalling and modulate root elongation, which may occur through a reduction in BR6ox1 and BR6ox2 mRNA levels. Taken together, our results reveal a role of BR signalling in root elongation under B deficiency.
The essential micronutrient boron （B） has key roles in cell wall integrity and B deficiency inhibits plant growth. The role of jasmonic acid （JA） in plant growth inhibition under B deficiency remains unclear. Here, we report that low B elevates JA biosynthesis in Arabidopsis thaliana by inducing the expression of JA biosynthesis genes. Treatment with JA inhibited plant growth and, a JA biosynthesis inhibitor enhanced plant growth, indicating that the JA induced by B deficiency affects plant growth. Furthermore, examination of the JA signaling mutants jasmonate resistant1, coronatine insensitive1‐2, and myc2 showed that JA signaling negatively regulates plant growth under B deficiency. We identified a low‐B responsive transcription factor, ERF018, and used yeast one‐hybrid assays and transient activation assays in Nicotiana benthamiana leaf cells to demonstrate that ERF018 activates the expression of JA biosynthesis genes. ERF018 overexpression （OE） lines displayed stunted growth and up‐regulation of JA biosynthesis genes under normal B conditions, compared to Col‐0 and the difference between ERF018 OE lines and Col‐0 diminished under low B. These results suggest that ERF018 enhances JA biosynthesis and thus negatively regulates plant growth. Taken together, our results highlight the importance of JA in the effect of low B on plant growth.
論文鏈接：
https://onlinelibrary.wiley.com/doi/10.1111/tpj.15311
https://academic.oup.com/jxb/article/72/8/3108/6126775
https://onlinelibrary.wiley.com/doi/10.1111/jipb.13048
日期：2021-05-11
油菜素甾醇（brassinosteroids, BRs）是一類多羥基的甾醇類植物激素，因首先從油菜花粉中發現提取而得名，廣泛分布在植物的根、莖、葉片、花、種子和幼嫩的生長組織中，調控植物的生長發育。植物缺硼會嚴重抑制主根的生長，該團隊通過研究分析擬南芥響應缺硼和BR的RNA-seq結果，發現兩者共表達的基因數高達45.9%（圖1c），且這些共表達的基因大部分呈現相反的表達趨勢。與野生型相比，BR的受體突變體bri1-119和bri1-301表現出對低硼脅迫不敏感，而BR信號增強突變體bes1-D對缺硼脅迫則表現出顯著高的抗性（圖1a）。此外，外源添加24-表油菜素內酯（eBL）能顯著緩解根的生長抑制（圖1b），而添加BR合成抑制劑BRZ會加重根生長的抑制，且缺硼減少了BES1的核信號，但在缺硼條件下添加eBL則能增加BES1的核信號。進一步研究發現缺硼通過抑制BR合成基因BR6ox1和BR6ox2的表達而減少了油菜素內酯（BL）的合成（圖1d）。
茉莉酸（JA）是調節植物生長發育、抵御逆境脅迫的一種植物激素。植物營養生物學團隊研究發現缺硼條件下擬南芥地上部和根中積累JA達到正常硼條件下的7.9倍和2.8倍，生長受嚴重抑制，外源添加JA合成抑制劑DIECA則可以緩解缺硼對生長的抑制。團隊進一步鑒定到一個缺硼誘導的乙烯轉錄因子ERF018，通過作用于JA合成基因AOCs的啟動子區域，上調了JA合成基因的表達，使JA合成增多。在茉莉酸氨基酸結合酶JAR1的作用下，增多的JA進一步轉變為有生物活性形式的茉莉酸-異亮氨酸JA-Ile。JA-Ile與受體復合物SCFCOI1結合激活JA下游信號，參與缺硼對擬南芥生長的抑制。同時，研究發現缺硼上調了乙烯（ET）合成基因的表達，使ET積累，并負調主根生長。JA通過抑制jar1-1突變體中乙烯信號轉錄因子EIN3的蛋白水平，從而實現JA與ET協同作用于缺硼對主根生長的抑制。JA并不直接調控硼的吸收轉運，而是通過影響缺硼時根系構型而影響硼的吸收。
上述研究獲得了國家自然科學基金、國家重點研發計劃和中央高校基本科研業務費專項基金資助，團隊成員汪社亮副研究員、王創研究員，丁廣大副教授，蔡紅梅副教授和石磊教授等參與了研究工作。
【英文摘要】
Brassinosteroids （BRs） are pivotal phytohormones involved in dominating root development. Boron （B） is an essential micronutrient for plants, and root growth is rapidly inhibited under B‐deficiency conditions. However, the mechanisms underlying this inhibition are still unclear. Here, we identified BR‐related processes underlying B deficiency at the physiological, genetic, molecular/cell biological and transcriptomic levels and found strong evidence that B deficiency can affect BR biosynthesis and signalling, thereby altering root growth. RNA sequencing analysis revealed strong co‐regulation between BR‐regulated genes and B deficiency‐responsive genes. We found that the BR receptor mutants bri1‐119 and bri1‐301 were more insensitive to decreased B supply, and the gain‐of function mutants bes1‐D and pBZR1‐bzr1‐D lines exhibited insensitivity to low‐B stress. Under B‐deficiency conditions, exogenous 24‐epibrassinolide （eBL） rescued the inhibition of root growth, and application of the BR biosynthesis inhibitor BRZ exacerbated this inhibitory effect. The nuclear‐localized signal of BES1 was reduced under low‐B conditions compared with B‐sufficiency conditions. We further found that B deficiency hindered the accumulation of brassinolide （BL） to downregulate BR signalling and modulate root elongation, which may occur through a reduction in BR6ox1 and BR6ox2 mRNA levels. Taken together, our results reveal a role of BR signalling in root elongation under B deficiency.
The essential micronutrient boron （B） has key roles in cell wall integrity and B deficiency inhibits plant growth. The role of jasmonic acid （JA） in plant growth inhibition under B deficiency remains unclear. Here, we report that low B elevates JA biosynthesis in Arabidopsis thaliana by inducing the expression of JA biosynthesis genes. Treatment with JA inhibited plant growth and, a JA biosynthesis inhibitor enhanced plant growth, indicating that the JA induced by B deficiency affects plant growth. Furthermore, examination of the JA signaling mutants jasmonate resistant1, coronatine insensitive1‐2, and myc2 showed that JA signaling negatively regulates plant growth under B deficiency. We identified a low‐B responsive transcription factor, ERF018, and used yeast one‐hybrid assays and transient activation assays in Nicotiana benthamiana leaf cells to demonstrate that ERF018 activates the expression of JA biosynthesis genes. ERF018 overexpression （OE） lines displayed stunted growth and up‐regulation of JA biosynthesis genes under normal B conditions, compared to Col‐0 and the difference between ERF018 OE lines and Col‐0 diminished under low B. These results suggest that ERF018 enhances JA biosynthesis and thus negatively regulates plant growth. Taken together, our results highlight the importance of JA in the effect of low B on plant growth.
論文鏈接：
https://onlinelibrary.wiley.com/doi/10.1111/tpj.15311
https://academic.oup.com/jxb/article/72/8/3108/6126775
https://onlinelibrary.wiley.com/doi/10.1111/jipb.13048
日期：2021-05-11
