【作者】 彭志红；

【导师】 任春梅；

【作者基本信息】 湖南农业大学 ， 遗传学， 2013， 博士

【摘要】 本文以拟南芥野生型Co1-0和Ws-2以及芸苔素(Brassinosteroid,BR)相关功能缺陷型突变体为实验材料,从芸苔素的生物合成和信号转导两个方面研究了芸苔素对茉莉素(Jasmonate,JA).CTK(Cytokinin,CTK)和糖诱导花青素积累的影响及其分子机理。主要研究结果如下：1.芸苔素调控JA诱导的花青素积累研究发现,芸苔素生物合成相关突变体pscl、dwf4-102和信号转导突变体bri1-4均因体内BR功能缺陷降低了JA诱导的花青素积累；同时,外源添加Brz抑制野生型拟南芥JA诱导的花青素积累,而添加epi-BL增加野生型拟南芥JA诱导的花青素积累。而且,经外源MeJA处理后,两类突变体植株花青素含量均会有所恢复,不过花青素增加量bril*4<dwf4-102,表明芸苔素在JA诱导花青素积累的过程中存在正调控作用,芸苔素可能是通过信号途径影响JA诱导的花青素积累。RT-PCR结果显示,芸苔素不影响JA诱导的花青素合成途径早期基因CHS和CHI的表达,主要是通过影响JA诱导的晚期基因DFR、LDoX和UF3GT的表达进行调控,并且,这种调控作用是通过MYB类转录因子PAP1、PAP2, bHLH类转录因子GL3的介导作用实现的。2.芸苔素调控CTK诱导的花青素积累研究发现,芸苔素相关突变体dwf4-102和bril-4降低了CTK诱导的花青素积累；同时,外源添加6-BA增加野生型拟南芥CTK诱导的花青素积累。而且,经外源6-BA处理后,两类突变体植株花青素含量均会有所恢复,不过花青素增加量bril-4<dwf4*102,这表明芸苔素通过信号途径正调控CTK诱导的花青素积累。通过Real-time PCR分析表明,CTK会诱导花青素合成途径的早期基因和晚期基因的表达,而芸苔素对CTK诱导的花青素合成途径早期基因的表达不会产生影响,是通过对晚期基因的表达进行调控来影响花青素的积累,并且,芸苔素是通过bHLH类转录因子GL3.EGL3调控CTK诱导的晚期基因的表达。此外,芸苔素信号受阻会上调CTK诱导的MYB类转录因子PAP2和WD40蛋白TTGl的表达。3.芸苔素影响糖诱导的花青素积累研究发现,芸苔素相关突变体dwf4-102和bril-4均降低了不同浓度蔗糖(30、60、90、120、150mM)诱导的花青素积累量。而外源epi-BL可以提高野生型糖诱导的花青素积累；恢复及促进dwf4-102糖诱导的花青素积累；不能恢复bril-4降低的糖诱导的花青素积累,表明芸苔素通过信号转导途径参与糖诱导的花青素积累。Real-time PCR分析显示,芸苔素对糖诱导的花青素合成途径早期基因PAL、 CHS和CHI的表达影响不明显,主要是通过调控晚期基因DFR.LDOX和UF3GT的表达介导对糖诱导花青素积累的影响,并且,芸苔素只通过介导MYB类转录因子PAP1、PAP2的表达调控糖诱导的晚期基因的表达,而bHLH类转录因子GL3.EGL3和WD40蛋白TTGl对此过程无没明显调控作用。上述研究的完成发现了芸苔素影响拟南芥幼苗花青素的生物合成,并探析了芸苔素调控JA.CTK和糖诱导的花青素积累的分子机理,对进一步揭示及完善植物花青素的生物合成和调控机理具有重要的理论价值和应用前景。更多还原

【Abstract】 In this paper, Wild types Col-0,Ws-2and dwf4-102, bril-4mutants were used to study the mechanism by which the cross-talks between brassinosteroid (BR) and jasmonate (JA) or cytokinin (CTK), sucrose regulate anthocyanin accumulation from the biosynthesis and signal transduction of brassinosteroids in Arabidopsis seedlings. The following is the main results:1. Brassinosteroid regulate JA-induced anthocyanin accumulationIn this study it was shown that the JA-induced anthocyanin accumulation was reduced in the BR mutants or wild type treated with brassinazole, an inhibitor of BR biosynthesis, whereas was promoted by an application of exogenous BR. It was also shown that the’late’anthocyanin biosynthesis genes including DFR, LDOX, and UF3GT, were induced slightly by jasmonate in the BR mutants relative to wild type. Moreover, the expression level of JA-induced MYB transcription factors such as PAP1, PAP2, and bHLH transcription factor GL3, was lower in the BR mutants than that in wild type. These results suggested that BR affects the JA-induced anthocyanin accumulation by regulating the’late’anthocyanin biosynthesis genes and this regulation might be mediated by MYB/bHLH transcription factors.2. Brassinosteroid regulate CTK-induced anthocyanin accumulationIn this study it was shown that the CTK-induced anthocyanin accumulation was reduced in the BR mutants, whereas was induced in wild type by treatment with exogenous BR. It was also shown that the expression of the’late’anthocyanin biosynthesis genes was reduced by cytokinins in the BR mutants, yet was increased in wild type. Furthermore, the expression level of CTK-induced bHLH transcription factors including GL3, EGL3, was lower in the BR mutants than that in wild type. These results indicated that BR affects the CTK-induced anthocyanin accumulation by regulating the ’late’ anthocyanin biosynthesis genes and this regulation might be mediated by bHLH ranscription factors. 3. Brassinosteroid affect sucrose-induced anthocyanin accumulationIn this study it was shown that the sucrose-induced anthocyanin accumulation was reduced in the BR mutants, but was enhanced in wild type by an application of exogenous BR. It was also shown that the’late’ anthocyanin biosynthesis genes including DFR, LDOX, and UF3GT, were induced slightly by sucrose in the BR mutants relative to wild type. Furthermore, the expression level of sucrose-induced MYB transcription factors such as PAP1, PAP2, was lower in the BR-insensitive mutant bril-4than that in wild type. However, the expression level of bHLH transcription factors such as GL3, EGL3, and WD-repeat protein TTG1remain unchange in both the bril-4mutant and wild type. Therefore, these results suggested that BR affects the sucrose-induced anthocyanin accumulation by regulating the’late’ anthocyanin biosynthesis genes and this regulation might be mediated by MYB transcription factors.更多还原