异源表达EgrNAC1提高拟南芥抗寒性和对干旱、高盐的敏感性

Ectopic Express of EgrNAC1 Enhances Cold Tolerance and Sensitivity to Drought and Salt in Arabidopsis thaliana

桉树是我国南方重要用材树种,但其栽培种对低温、干旱和高盐等非生物逆境抗性弱,限制了其栽培范围的扩大和栽培效益的提高。EgrNAC1(Eucgr.I00058)是巨桉中受低温、干旱和高盐诱导表达的NAC类转录因子。为进一步研究EgrNAC1的功能,通过异源转化拟南芥,获得了超表达EgrNAC1的转基因纯合株系,并对其进行低温(-6℃)、干旱、高盐(NaCl 300 mmol·L^(-1))和脱落酸(0.5μmol·L^(-1))处理,分析转基因株系对非生物逆境的响应。结果表明,超表达EgrNAC1能提高拟南芥植株对低温的抗性。-6℃处理12 h,恢复5 d后,转基因株系EgrNAC1-OE1和EgrNAC1-OE8的存活率分别达到88.9%和81.5%,而野生型仅有29.6%。低温处理下,转基因株系中3个低温信号传导(CBF)途径相关的基因,AtCBF1、AtCBF2和AtRD29A的表达量相对于野生型显著上调;超表达EgrNAC1提高了转基因植株对干旱和高盐的敏感程度。同时,转基因植株相对于野生型表现出对ABA敏感性的下降。综上,EgrNAC1在巨桉低温响应中可能作为一个正向调控因子,通过参与调控CBF途径中低温响应相关基因的表达,提高植物在低温逆境下的适应性。但在干旱和高盐逆境下,EgrNAC1可能发挥负调控作用,且这种作用可能与ABA的影响有关。本研究结果为深入了解桉树EgrNAC1的功能以及开展桉树抗逆分子辅助育种提供了一定的理论参考。

Eucalyptus is a very important economic tree species in southern China.However,most cultivated Eucalyptus is sensitive to abiotic stresses such as low temperature,drought and salinity,which limit its planting region and the improvement of cultivation benefits.EgrNAC1(Eucgr.I00058)is a NAC-like transcription factor gene in Eucalyptus grandis which is induced by low temperature,drought and salt treatment.To further explore its function in abiotic stress response,homozygous transgenic lines that overexpressed EgrNAC1 were obtained by ectopic expression in Arabidopsis thaliana.And,subjected to low temperature(-6℃),drought,high salt(300 mmol·L^(-1) NaCl)and ABA(0.5μmol·L^(-1))treatment,the responses of transgenic lines to these abiotic stress were analyzed.The results showed that overexpression of EgrNAC1 in Arabidopsis could increase the tolerance of plants to low temperature.After 12 hours treatment at-6℃and then 5 days of recovering,the survival rate of the transgenic lines of EgrNAC1-OE1 and EgrNAC1-OE8 were 88.9%and 81.5%respectively,while only 29.6%for wild type.Further analysis showed the expression levels of three CBF pathway related genes AtCBF1,AtCBF2 and AtRD29A were significantly up-regulated in the EgrNAC1 over-expression lines under low temperature.On the other hand,sensitivity to drought and salinity in transgenic plants were increased and ABA sensitivity showed a decrease compared to wild type These results implied that EgrNAC1 possibly act as a positive regulator in the low temperature response through regulating the expression of genes invoved in ICE-CBF pathway in Eucalyptus grandis,thereby improving the resistance of plants to low temperature stress.However,under drought and high salt stress,EgrNAC1 may play a negative regulatory role,and ABA signal transduction possibly be involved in this regulation process.This study provides valuable information for elucidating of the function of EgrNAC1 and benefits for molecular-assisted breeding of abiotic stress-resistance in Eucalyptus.