生命科学学院知识库

植物作为固着生物，其分布，生长和发育受环境因子影响。温度是一种重要因子，但是对于非胁迫温度如何调控植物生长发育的分子机制的认识至今知之甚少。我们的研究发现相比于野生型Col-0，拟南芥ckrc1-1突变体是对高温更敏感和对低温较不敏感的突变体。在22 ℃和27 ℃条件下，ckrc1-1的根长均显著变短，随着温度的升高根的向重力性缺失增强，在27 ℃条件下外源的NAA处理可以恢复ckrc1-1至同激素处理的Col-0的表型，但IAA不能恢复。外源的ACC均可以恢复22 ℃和27 ℃的ckrc1-1的根长和根卷曲至同激素处理的Col-0的表型，而AVG可以增强ckrc1-1的根卷曲度，并抑制根生长；在17 ℃条件下，ckrc1-1的根长相较于Col-0明显伸长，外源乙烯和生长素化学互补实验表明生长素、乙烯和生长素极性运输同样参与低温调控过程。通过比较不同温度（17 ℃、22 ℃和27 ℃）调控生长素和乙烯的响应机制发现：相关信号的响应和信号间的相互作用在不同温度下是不同的。根内，生长素信号随着温度的增加而增强，但是乙烯信号从17 ℃到22 ℃，22 ℃到27 ℃的变化呈现出“V”型的趋势。
通过分析17 ℃，22 ℃和27 ℃条件下相应处理下的Col-0和ckrc1-1的根的分生区（RM）和成熟区细胞（CDZ）的长度，发现17 ℃条件下乙烯抑制根的细胞伸长过程中CKRC1不发挥重要作用；22 ℃和27 ℃条件下， CKRC1发挥重要作用。乙烯通过ETR1途径调控ckrc1-1不同温度下的根生长。并且高温可以通过增强的ETR1介导的乙烯信号通路CKRC1的表达；低温也能增强ETR1介导的乙烯信号通路，但增强的乙烯信号不能促进CKRC1的表达。通过分析相关超表达株系和突变体的表型，发现不同温度下，aux1的根部表型类似于ckrc1-1的表型，都是对高温更敏感和低温较不敏感的突变体,pin2对不同温度均更不敏感；CKRC1，AUX1和PIN2在不同温度下通过影响根的不同区域调控根伸长，AUX1、PIN1和PIN2参与不同温度下ckrc1-1的根向重力性响应，同时在这一过程中CKRC1依赖的生长素信号对维持AUX1,PIN1和PIN2的表达有至关重要的作用。
综上所述，我们的研究表明生长素和乙烯的相互作用及其相互作用所介导的生长素极性运输在植物根生长响应不同温度过程中发挥着重要作用。

Plants are sessile organisms, and temperature is a key environmental factor affecting plant distribution, growth and development. However，little is known about the molecular mechanisms underlying such developmental plasticity modulated by temperature.Our results show that the Arabidopsis ckrc1-1 mutant is more sensitive to higher temperature and less sensitive to lower temperature than Col-0. At 22 ºC and 27 ºC, the ckrc1-1 root length is significantly shortened and the root gravity defect is enhanced with improved temperature in comparison to Col-0, changes that can be restored with addition of 1-Naphthaleneacetic Acid (NAA), but not Indole-3-Acetic Acid (IAA) at elevated temperature. Addition of 1-Aminocyclopropane-1-carboxylic acid(ACC) can restored ckrc1-1 root length and root curling at 22 ºC and 27 ºC, while Aminoethoxyvinylglycine(AVG) can enhance ckrc1-1 root curling and inhibit root length. At 17ºC, ckrc1-1 root length is more longer than Col-0, related experiments indicate that auxin, ethylene and polar auxin transport regulate ckrc1-1 response to lower temperature.
Comparison of the regulatory mechanisms of ckrc1-1 root growth at different temperatures (17 ºC, 22 ºC, 27 ºC), show that the interaction between signals (auxin and ethylene) and the effects of downstream genes differ at different temperatures. It appears that in the root, auxin signal increases with increasing temperature from lower to higher temperature, and ethylene signal varies from 17 °C to 22 °C and 22 °C to 27 °C in a "V" trend.Analyzing the length of the meristem zone (MZ) and the cell length of the differentiation zone (DZ) appears that CKRC1 does not play an important role in inhibiting root cell elongation by ethylene at 17 °C, but plays an important role at 22 °C and 27 °C. Higher temperature can promote CKRC1-dependent auxin biosynthesis by enhancing ETR1-mediated ethylene signaling. Low temperature-enhanced, ETR1-mediated ethylene signaling could not promote the expression of CKRC1.
 Though analyzing the phenotype of overexpression lines and mutants, we find that the root growth in aux1 is similar to the phenotype of ckrc1-1 which is more sensitive to higher temperature and less sensitive to lower temperature than Col-0, pin2 is less sensitive to both temperatures; CKRC1, AUX1, and PIN2 regulate root elongation by affecting different regions of the root at different temperatures. AUX1, PIN1 and PIN2 are involved in the ckrc1-1 root gravity response under different temperatures. Further, CKRC1-dependent auxin biosynthesis is critical for maintaining AUX1, PIN1 and PIN2 expression.Our research suggests that the interaction between auxin and ethylene and that the interaction-mediated polar auxin transport play important roles during the plant root growth response to different temperatures.