烟草乙烯反应突变体的抗冷性及机理分析

摘要

为了深入研究乙烯在植物抵抗逆境胁迫中的作用,以烟草为模式植物,利用幼苗对外源乙烯的“三重反应”,筛选得到了40多个乙烯不敏感突变体,其中多数突变体具有较强的抗冷性;从中选取4个突变体株系,对它们耐受低温胁迫的生理基础和作用机理进行了分析.结果表明,低温(0℃)胁迫下,烟草乙烯不敏感突变体的电解质渗透率显著低于野生型,而抗氧化酶活性(POD、SOD)以及过氧化氢酶(CAT)活性都高于野生型,说明突变体具有抵抗低温胁迫的优势生理基础.进一步研究发现,低温(0℃)胁迫下,烟草突变体中冷诱导基因NtCBFs和NtCOR47呈现高水平表达,乙烯信号传导途径中下游基因ERFs的表达也发生显著变化.这些研究为烟草乙烯不敏感突变体株系具有较强的抗冷性提供了直接的分子证据.%To study the regulatory function of ethylene in plant stress tolerance,over 40 ethylene insensitive tobacco mutants were obtained from a genetic screen based on the typical seedling phenotype to ethylene in darkness,named " triple response",and most of the mutants displayed chilling resistance.The present study chose 4 mutant strains for further analyses in their chilling tolerance,physiological basis,and cold-regulated gene expressions.Under low temperature (0 ℃) stress,the electrolyte permeability of the tobacco ethylene insensitive mutants was significantly lower than that of the wild type,while the activities of SOD,POD and catalase were higher than those of the wild type.Further study indicated that the cold-induced genes showed highly transcription level under low tempera ture (0 ℃) stress.And,the transcripts levels of the downstream ERFs in the ethylene signal transduction pathway in the mutants were altered in the tobacco mutants.These data provide a direct molecular evidence for the strong resistance of the tobacco ethylene insensitive mutants to chilling stress.This study not only provides a new evidence for the relationship between ethylene signaling and chilling stress,but also lays a foundation for the use of biotechnology to improve crop stress resistance.