生长素和乙烯互作调控硝酸铵诱导的根毛分叉

以野生型拟南芥(WT)及其生长素和乙烯不敏感型突变体(aux1-7、axr1-3、etr1-1和etr1-3)为实验材料,采用固体培养法研究了高浓度硝酸铵对根毛发育的影响,以揭示其调控根毛发育的机制。结果表明:(1)随着外源硝酸铵浓度的逐渐增加,拟南芥根毛伸长受阻,产生大量的分叉根毛。(2)高浓度硝酸铵条件下,外源活性氧或活性氧产生抑制剂二苯基氯化碘(DPI)的添加能抑制高浓度硝酸铵诱导的分叉根毛产生。(3)高浓度硝酸铵条件下,外源生长素或乙烯合成前体物质1-氨基-环丙烷-1-羧酸(ACC)处理能恢复根毛的正常生长,解除高浓度硝酸铵诱导根毛分叉现象。(4)高浓度硝酸铵条件下,外源生长素处理乙烯不敏感型突变体或ACC处理生长素不敏感型突变体均能抑制突变体分叉根毛的形成。研究表明,活性氧、生长素和乙烯都参与了高浓度硝酸铵对根毛发育的过程调控;在硝酸铵诱导的根毛分叉中生长素和乙烯存在相互作用,在缺乏生长素信号通路时,乙烯能够发挥补充作用抑制分叉根毛的产生;在缺乏乙烯信号通路时,生长素也可以弥补缺失乙烯的作用抑制根毛的分叉,但是需要更高浓度的生长素才能充分抑制分叉根毛的产生。

Interaction between Auxin and Ethylene in the Regulation of NH4NO3 induced Branched Root Hair Formation

To explore the possible mechanism of high rates of ammonium nitrate (NH₄NO₃) in the regulation of root hair formation, we grew wild type (WT), auxin insensitive and ethylene insensitive mutant seedlings on vertically oriented agar plates. Our study found that: (1) high rates of ammonium nitrate (NH₄NO₃) supply stimulated the branched root hair formation and inhibited root hair elongation. (2) The effect of NH₄NO₃ on root hair formation were blocked by reactive oxygen species (ROS) and diphenylene iodonium chloride (DPI), suggesting that ROS was involved in NH₄NO₃ induced branched root hair formation. (3) The treatment of auxin or ethylene under high NH₄NO₃ condition completely inhibited high NH₄NO₃ induced branched root hair formation. (4) Either eir1 3 seedlings treated with auxin or aux1 7 and axr1 3 treated with ACC, the NH₄NO₃ induced branched root hair formation was inhibited. The results above showed that ROS, auxin and ethylene involved in high NH₄NO₃ induced branched root hair formation. Auxin played a compensating role in the absence of an ethylene response and ethylene played a supplemental role in the absence of an auxin response. A higher level of auxin was required for preventing branched root hair formation in the absence of ethylene signaling.