【作者】 李妍；

【导师】 刘选明； 林辰涛；

【作者基本信息】 湖南大学 ， 生物化学与分子生物学， 2008， 硕士

【摘要】 在高等植物体内,至少存在三种光受体捕捉光信号:光敏素,蓝光/UV-A受体和UV-B受体,每一种光受体吸收不同光谱的光。光经信号转导后进入植物生长发育阶段影响一系列生长过程如种子萌发,幼苗生长以及开花时间等。拟南芥幼苗生长过程已成为研究植物光信号转导到形态建成机制的模式系统。隐花素(cryptochrome)是植物感受蓝光的蓝光受体,它介导蓝光调节植物的光形态建成反应,如抑制下胚轴伸长、促进子叶伸展及调节开花等。除了光受体的作用外,已知许多激素包括生长素,赤霉素(Gibberellin,GA),乙烯和细胞分裂素也能调节植物生长。光对GA水平的改变也会影响植物生长过程,还不清楚蓝光下GA调节植物光形态建成反应。为了研究蓝光下赤霉素对拟南芥光形态建成的影响,我们用模式植物拟南芥过表达35S::GFP-GA2ox8-1、35S::GFP-GA2ox8-8的突变体株系和以cry1cry2突变体为背景的T-DNA插入突变体scc7-D(suppressors of cry1cry2 7-dominant)作为研究对象进行分析,在蓝光下,过表达GA2ox8基因的scc7-D、35S::GFP-GA2ox8-1、35S::GFP-GA2ox8-8的突变体表现出抑制下胚轴伸长,较大的茎尖角度和子叶张开角度等表型。由于缺少蓝光受体cry1和cry2,cry1cry2、scc7-D突变体表现出对蓝光不敏感,花青素和叶绿素的含量分析结果也说明隐花素能通过介导蓝光调节GA控制部分去黄化表型。去黄化表型分析结果与光调节基因CHS、RBCS、CAB2基因表达水平的分析结果一致,同时蓝光下GA水平降低的植物中不正常表达光依赖基因。这些研究结果都说明了隐花素通过调节GA抑制光形态建成,至少是在幼苗早期的阶段。光是植物生长重要的环境因素。为了研究光和赤霉素对木质素生物合成的影响,本文从植物的光受体着手,以拟南芥的几种不同光受体突变体:红光、远红光受体突变体(phyA,phyB,phyAphyB),蓝光受体突变体(cry1,cry2,cry1cry2)和赤霉素生物合成突变体(scc7-D,35S::GFP-GA2ox8-1,35S::GFP-GA2ox8-8)为材料,采用溴乙酰紫外分光光度法测定不同的光受体突变体的木质素含量,同时采用间苯三酚染色,观察这些光受体突变体的茎切片。通过上述分析方法研究了不同光受体突变对木质素生物合成的影响。结果发现,与野生型相比,远红光受体突变体和红光受体突变体的木质素含量偏低,蓝光受体突变体则偏高。这些研究结果说明远红光和红光促进木质素生物合成,蓝光抑制木质素的合成。用RT-PCR和Q-PCR分析木质素生物合成途径酶基因的表达,发现光敏素phyA,phyB介导远红光/红光调节木质素合成是通过调节4CL3基因表达,而蓝光受体cry1、cry2不是通过4CL3基因调节木质素合成,可能存在其它信号通路调节木质素生物合成。此外,用外源赤霉素短时处理拟现芥叶柄的实验,证明了赤霉素可以影响木质素的合成。更多还原

【Abstract】 In higher plants, there are at least three kinds of light receptors to capture light signal: phytochrome, cryptochromes and phototropin, which receptor absorb different spectrum of light. The light signal transduction and then entered the stage of plant growth and development, such as seed germination, seedling growth and flowering time. The growth process of Arabidopsis seedlings has become a model system for researching photomorphogenic mechanism. Cryptochromes are blue light receptors that regulate various photomophogenic responses in plant, including inhibition of hypocotyl elongation, stimulation of cotyledon expansion, and regulation of flowering time. It is not clear about how cryptochromes mediate blue light regulating photomophogenic responses, such as inhibition of hypocotyl elongation. Many hormones, including IAA, Gibberellin(GA), ethylene and cytokinin also regulate plant growth as well as light. In addition, light also regulates plant growth by changing GA levels.At present, it is not clear about photomophogenic mechanism how blue light regulate plant grow.To determine the effect of GA on photomorphogenesis in Arabidopsis under blue light, overexpression lines 35S::GFP-GA2ox8-1, 35S::GFP-GA2ox8-8 lines in wild type (WT) Col-4 background and an activation-tagging mutant scc7-D (suppressor of cry1cry2) were used in this research. Our results indicated that compared to cry1cry2, scc7-D showed a phenotype of inhibition of hypocotyl elongation, cotyledons opening and remaining larger hook angle under blue light; 35S::GFP-GA2ox8-1, 35S::GFP-GA2ox8-8 overepression lines also have short hypocotyls and opening cotyledons contrast with WT. cry1cry2 and scc7-D displayed insensitive to blue light are the result of lacking of cry1 and cry2. It was demonstrated that cryptochromes mediate GA regulation of de-etiolated seedlings by analysing chlorophyll and anthocyanin content of seedlings. In agreement with this, light-dependent gene expression, such as CHS、RBCS、CAB2, showed misregulating of light-depended gene in Arabidopsis with reduced GAs level in blue light. These results suggest that cryptochrome may regulate GA response to supresss photomorphogenesis, at least at its early stages.Light is an important environmental factor in plant growth. To study the light and GAs effecting on lignin biosynthesis, many Arabidopsis mutants including red/far-red-light receptor mutants (phyA, phyB , PhyAphyB), blue-light receptor mutants (cry1, cry2, cry1cry2) and GA Biosynthesis mutants (scc7-D, 35S::GFP-GA2ox8-1, 35S::GFP-GA2ox8-8) were used in our paper. The method of bromine acetyl was adopted in measuring different lignin contents in light receptor mutants, and the section of the stem were observed by phloroglucinol staining. We investigated the effects on lignin biosynthesis in different light receptor mutants through above methods. The results showed that compared with WT, lignin contents in red/far-red-light receptor mutants were lower, but the blue-light receptor mutants were higher. These results preliminary suggested that red/far-red-light promoted the lignin biosynthesis, whereas blue light inhibited the lignin biosynthesis. By analysis genes in lignin biosynthesis through RT-PCR and Q-PCR, we found that phyA, phyB-mediated far-red light or red light regulate lignin biosynthesis through regulating 4CL3 expression, but for cry1, cry2 regulating lignin biosynthesis,there may be other signaling pathway not by 4CL3 gene. Additionally, short-term GA3 treatment of petioles of mature plant also proved that GA may also effct the lignin biosynthesis.更多还原