Enhanced brassinosteroid signaling intensity via SlBRI1 overexpression negatively regulates drought resistance in a manner opposite of that via exogenous BR application in tomato
Enhanced brassinosteroid signaling intensity via SlBRI1 overexpression negatively regulates drought resistance in a manner opposite of that via exogenous BR application in tomato
复制标题
通过 SlBRI1 过表达增强油菜素类固醇信号强度，以与在番茄中应用外源 BR 相反的方式负向调节耐旱性
DOI：
10.1016/j.plaphy.2019.02.014
复制
发表时间：
2019-05-01
影响因子：
6.5
通讯作者：
Wang, Xiaofeng
中科院分区：
文献类型：
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作者：
Nie, Shuming;Huang, Shuhua;Wang, Xiaofeng
类甾醇（BRs）调节植物生长和胁迫反应。BRASSINOSTEROID-INSENSITIVE 1（BRI 1）是一种BR受体，可感知BR并随后激活BR信号传导。然而，BR含量和BRII表达水平如何影响番茄的抗旱性需要进一步研究。在这里，我们将24-表油菜素（EBR）和油菜素（Brz）外源施加到番茄植株上，并产生不同的转基因番茄SlBRII过表达系，以研究干旱胁迫反应。结果表明，干旱胁迫前3 d施用EBR，可提高叶片BR含量，降低脱落酸（阿坝）和活性氧（ROS）含量，干旱胁迫后气孔开度提高，抗旱性增强。Brz处理降低了抗旱性。令人惊讶的是，过表达35 S：SlBRI 1，增加BR信号强度，导致阿坝和ROS含量略有提高，最终降低气孔孔径和抗旱性。此外，表达由胁迫诱导型启动子（Atrd 29 A）驱动的SlBRII的植物也表现出降低的植物抗旱性。在所有情况下，增强BR信号强度降低抗氧化酶活性，减少干旱胁迫相关基因的表达，最终损害抗旱性。此外，具有改变的油菜素敏感性（abs）的SlBRII突变体（其是弱BR信号传导）表现出显著增加的抗旱性。因此，我们的研究结果表明，BR含量正调控番茄的抗旱性，BR信号强度通过BRI 1与抗旱性呈负相关。这意味着BRs引起的抗旱性增强是一个新发现的BR信号分支，位于BRs下游，与BRI 1不同。
Brassinosteroids (BRs) regulate plant growth and stress responses. BRASSINOSTEROID-INSENSITIVE 1 (BRI1) is a BR receptor that perceives BRs and subsequently activates BR signaling. However, how BR contents and BRII expression levels affect the drought resistance of tomato requires further investigation. Here, we exogenously applied 24-epibrassinolide (EBR) and brassinazole (Brz) to tomato plants and generated different transgenic tomato SlBRII overexpression lines to study the drought stress response. Our results showed that EBR application 3 days before drought stress increased the contents of BRs and decreased abscisic acid (ABA) and reactive oxygen species (ROS), after which stomatal aperture and drought resistance eventually increased. Brz application reduced the drought resistance. Astonishingly, overexpression of 35S:SlBRI1, which increased BR signaling intensity, led to slightly improved contents of ABA and ROS and ultimately reduced both stomatal aperture and drought resistance. Moreover, plants expressing SlBRII driven by a stress-inducible promoter (Atrd29A) also exhibited reduced plant drought resistance. In all cases, enhancing the BR signaling intensity reduced antioxidant enzyme activity and reduced the expression of drought stress-related genes, ultimately compromising the drought resistance. Additionally, SlBRII mutants with altered brassinolide sensitivity (abs), which was weak BR signaling, exhibited significantly increased drought resistance. Therefore, our results reveal that BR contents positively regulated tomato drought resistance and that BR signaling intensity via BRI1 was negatively related to the drought resistance. These imply that the increased drought resistance in response to BRs is a newly discovered BR signaling branch that is located downstream of BRs and that differs from that of BRI1.