ABSTRACT

The gaseous phytohormone ethylene plays versatile roles in sustaining plant growth and fitness in response to environmental changes, such as light illumination, flooding, and mechanical pressure. Interestingly, it is well known that the effects of ethylene on plant growth vary profoundly, depending on external conditions. For example, light/dark conditions alter the directionality of ethylene action on hypocotyl growth. Similarly, a recent study has shown that the effects of ethylene on hypocotyl growth are reversed during temperature increases: ethylene attenuates hypocotyl elongation in the light at warm temperatures (28°C), while promoting it at normal temperatures (22°C). The ethylene-activated ETHYLENE-INSENSITIVE 3 (EIN3) transcription factor directly promotes the transcription of both PHYTOCHROM INTERACTING FACTOR 3 (PIF3) and ARABIDOPSIS PP2C CLADE D7 (APD7) genes. At 22°C, the auxin activity is tuned down, and thus ethylene promotes hypocotyl growth via the PIF3-mediated microtubule reorganization. On the other hand, when auxin highly accumulates at 28°C, the ethylene-directed growth repression is potentiated through the APD7-mediated repression of auxin responses. APD7 plays a role in integrating ethylene cues into auxin signaling. We propose that the dual mode of EIN3-mediated ethylene actions enables plants to optimize growth under constantly changing environments.

摘要

气态植物激素乙烯在维持植物生长和适应环境变化（如光照、洪水和机械压力）方面发挥着多种作用。有趣的是，众所周知，乙烯对植物生长的影响因外部条件而异。例如，光照/黑暗条件会改变乙烯作用于下胚轴生长的方向性。同样，最近的一项研究表明，乙烯对下胚轴生长的影响在温度升高时会逆转：乙烯在温暖的温度（28°C）下减弱光照下的下胚轴伸长，而在常温（22°C）下促进它。乙烯激活的乙烯不敏感 3 (EIN3) 转录因子直接促进PHYTOCHROM INTERACTING FACTOR 3的转录( PIF3 ) 和ARABIDOPSIS PP2C CLADE D7 ( APD7 ) 基因。在 22°C 时，生长素活性降低，因此乙烯通过 PIF3 介导的微管重组促进下胚轴生长。另一方面，当生长素在 28°C 高度积累时，乙烯定向的生长抑制通过 APD7 介导的生长素反应抑制得到加强。APD7 在将乙烯信号整合到生长素信号传导中发挥作用。我们建议 EIN3 介导的乙烯作用的双重模式使植物能够在不断变化的环境中优化生长。