木薯MeMYC2.2基因耐低温功能研究

Cold Resistance Function Analysis of Cassava MeMYC2.2

MYC2(MYeloCytomatosis)转录因子是植物应对逆境胁迫过程中茉莉酸信号传导相关的核心转录因子。本研究旨在初步分析木薯MeMYC2.2基因在低温胁迫响应中的功能。利用生物信息学分析木薯MeMYC2.1和MeMYC2.2基因的结构及其编码蛋白的理化性质;通过定量PCR分析了上述2个基因在木薯组培苗叶片中对低温胁迫的响应;通过转基因拟南芥研究MeMYC2.2的抗冻功能。木薯组培苗叶片中2个MeMYC2基因的表达均在低温胁迫早期被诱导,其中,与MeMYC2.1相比,MeMYC2.2差异表达更显著。MeMYC2.2蛋白主要定位于细胞核中,且在酵母中具有明显转录自激活功能,表明该蛋白具有转录因子特性。与野生型相比,过表达MeMYC2.2的转基因拟南芥抗冻能力显著提高。在低温处理下,CBF3基因在转基因拟南芥中的表达量要明显高于其在野生型的表达量,但另外3个CBF基因在转基因拟南芥中的表达量明显下降。木薯MeMYC2.2的表达受低温和茉莉酸调控,可以提高植物的抗冻性,且可能影响CBF基因对低温的响应。本研究为进一步利用MeMYC2基因改良木薯的低温耐受性奠定了理论基础。

Jasmonic acid(JA)signal transduction is a key pathway in plant response to stresses,in which MYC2(MYeloCytomatosis)plays an important role.This study aims to investigate the function of MeMYC2.2 from cassava(Manihot esculenta Crantz)under cold stress.Bioinformatics was used to identify the structures and physicochemical properties of two MYC2 gene,namely MeMYC2.1 and MeMYC2.2 from cassava.Quantitative PCR was to analyze the responses of them in the leaves of tissue-cultured cassava seedling to cold stresses.Furthermore,the function of MeMYC2.2 for cold resistance was verified in transgenic Arabidopsis.As result,the expressions of two MeMYC2 genes were dramatically induced under early cold stress in the leaves of tissue-cultured cassava seedling,and the differential expression of MeMYC2.2 was more significant compared to MeMYC2.1.The MeMYC2.2 protein was predominantly localized in the nucleus and presented of transcriptional activation ability in yeast,suggesting this protein probably was characterized of a transcription factor.Over-expression of MeMYC2.2 resulted in significant improvement of freezing tolerance in transgenic Arabidopsis compared to wild one.Furthermore,the expression of CBF3 was significantly up-regulated by MeMYC2.2 transgenic in Arabidopsis under cold conditions.However,expressions of other three CBF genes were down-regulated by MeMYC2.2 transgenic Arabidopsis under cold conditions.The expression of MeMYC2.2 was regulated by cold and jasmonic acid,which may increase its cold tolerance and affect the responses of CBF genes to cold stress.This study lays a theoretical foundation in using MeMYC2.2 to improve cold resistance in cassava cultivars.