陆地棉GhPYR1基因的克隆和功能分析

植物激素脱落酸(Abscisic acid,ABA)在植物应对干旱、盐碱等逆境胁迫以及植物种子萌发、根伸长、芽休眠等阶段发挥重要作用。PYR/PYL/RCAR蛋白家族是ABA受体,与ABA结合后能够启动ABA信号传导通路,诱导ABA应答基因的表达。利用电子克隆和RT-PCR技术从陆地棉中克隆了Gh PYR1基因,其编码的Gh PYR1蛋白与拟南芥中At PYR1蛋白相似度为73%。将Gh PYR1蛋白序列与拟南芥14个PYR/PYL/RCAR家族成员蛋白序列进行比对并构建进化树,发现它与拟南芥PYR/PYL/RCAR蛋白亚家族III亲缘关系最近。过表达Gh PYR1基因的T3代拟南芥在外源ABA处理下,其种子萌发和初期根生长均滞后于野生型,表现出对ABA更加敏感;高盐和干旱胁迫对转基因种子的萌发抑制更强烈,但苗期胁迫处理下转基因拟南芥的长势却明显优于野生型;同时在外源ABA诱导条件下ABA应答基因RD29A、RAB18的表达量较野生型有明显提高。以上结果说明Gh PYR1基因编码的蛋白是ABA的受体,过表达该基因能够提高植物对ABA的敏感性和增强应对逆境胁迫的能力。     

木醋液与6-苄基腺嘌呤对拟南芥生长的影响研究(英文)

木醋液(Wood vinegar,WV)作为植物生长调节类似物广泛应用于农业,但其促进植物生长的分子机制却鲜为人知。为了解木醋液(Wood vinegar,WV)促进植物生长的机理,以不同浓度木醋液/6-苄基腺嘌呤(6-BA)处理不同时间的模式生物拟南芥为材料,采用半定量PCR方法检测拟南芥调节应答因子(ARR4、ARR5、ARR6、ARR7、ARR9、ARR15)的表达量并以观察测量等方法比较木醋液和6-BA对拟南芥幼苗生长的宏观影响。研究结果显示,在调节拟南芥生长过程中,WV具有6-BA类似调节模式,但其总体效应弱于6-BA。在形态学方面,木醋液抑制叶片的展开,阻止子叶的发生,促进根的伸长并抑制侧根的形成。这些研究发现进一步完善了WV在分子水平调控植物生长的机制,对于WV在农业生产方面更加科学而广泛的应用具有重要的意义。     

细胞分裂素结合蛋白的研究进展

迄今为止,已从多种植物中分离到细胞分裂素结合蛋白(CBPs),它们可能在细胞分裂素的信号转导、体内运输及代谢中起作用。根据现有研究结果认为,大多数CTKs受体可能位于膜上,通过与G_蛋白耦联的信号转导系统或双组分信号转导系统完成CTKs信号的跨膜转导。少数CTKs受体可能位于细胞质中,与胞内CTKs结合后进入细胞核,直接调节基因的表达。本文综述了近年来对CBPs的研究进展,分析了CTKs受体的可能类型及CBPs作用的可能机制。     

细胞分裂素信号转导研究进展

对应用突变体研究细胞分裂素信号转导、细胞分裂素受体以及参与细胞分裂素信号转导相关的蛋白质作了简要介绍 ;并且对细胞分裂素信号途径进行了推测 :细胞分裂素被受体 (CKI1、IBC6或者GCR1 )接受后 ,经传导系统转化形成特定的信息 ,一方面可能调节基因的表达 ,从而可能调节受体水平 ,导致细胞对细胞分裂素浓度应答范围发生改变 ,另外 ,基因表达使细胞产生相关的生理反应 ;另一方面形成的特定信息可能激活MAPK级联途径 (mitogen_activatedproteinkinasecascade) ,导致细胞产生相关的生理反应。     

沙达旺上、下胚轴切段培养成再生植株

植物名称:沙达旺(Astragus adsurgenss)。材料类别:上胚轴及下胚轴。种子相继经0.1％昇汞溶液浸泡10分钟,自来水冲洗10分钟、漂粉精溶液(2g有效氯/100ml)浸泡20分钟进行表面消毒,以无菌水洗涤后在MS培养基上萌发。取初展真叶的幼苗,截取上、下胚轴,切成约5mm的切段作为培养材料。培养条件:外植体培养在附加不同的细胞分裂素(ZT或BA)或再加不同生长素(IAA或NAA)的     

细胞分裂素结合蛋白的研究进展

迄今为止,已从多种植物中分离到细胞分裂素结合蛋白（ＣＢＰｓ）,它们可能在细胞分裂素的信号转导、体内运输及代谢中起作用。根据现有研究结果认为,大多数ＣＴＫｓ受体可能位于膜上,通过与Ｇ－蛋白耦联的信号转导系统或双组分信号转导系统完成ＣＴＫｓ信号的跨膜转导。少数ＣＴＫｓ受体可能位于细胞质中,与胞内ＣＴＫｓ结合后进入细胞核,直接调节基因的表达。本文综述了近年来对ＣＢＰｓ的研究进展,分析了ＣＴＫｓ受体的可能     

6-BA拮抗脱落酸缓解渗透胁迫对种子萌发的抑制

细胞分裂素促进细胞分裂、芽的分化,拮抗脱落酸抑制的种子萌发,而细胞分裂素合成基因Ipt84在种子萌发过程中发挥重要的作用。本文分别用120mmol·L-1 NaCl和240mmol·L-1 甘露醇模拟盐和干旱胁迫处理拟南芥种子,探讨6一BA拮抗ABA对其抑制种子萌发和萌发后生长的影响。结果表明,细胞分裂素合成相关突变体ipt6-1、ipt6-2、ipt8．1和ipt8-2的种子萌发和生长可被NaCl和甘露醇显著抑制;而ABA合成相关突变体aba2-1对相同浓度NaCl和甘露醇的处理表现相对不敏感。进一步研究发现添加外源6一BA可恢复ipt6-1、ipt6-2、ipt8-1和ipt8—2的相关敏感表型,并且随6-BA浓度的增加,恢复效果也愈趋明显。     

植物种子特异基因调控网络研究

通过比较种子植物与蕨类植物的基因及其调控网络,为研究种子性状出现的分子机制提供更多的信息.下载拟南芥(Arabidopsis thaliana)种子特异基因和基因网络数据,构建拟南芥种子特异基因调控网络,并与江南卷柏(Selaginella moellendorffii)基因组数据比较,发现其中重要的调控节点.分析得到构成调控网络的1053个拟南芥种子特异基因,其中的969个基因形成一个复杂的调控网络.该网络的核心模块包括39个基因,形成哑铃状的子网络,其中重要节点基因AT1G54860只存在于种子植物基因组中.AT1G54860基因编码GPI锚定蛋白,参与细胞壁的形成、细胞间信号传导及生长分化等过程,推测其在种子形成中具有重要地位,可能起了"开关"的作用.     

小拟南芥ApZFP基因异源超表达促进拟南芥开花并提高耐逆性

锌指蛋白(ZFP)是一类重要的转录因子, 广泛参与植物的生长发育和非生物胁迫应答。新疆小拟南芥(Arabidopsispumila)又名无苞芥, 是十字花科短命植物, 具有高光效、繁殖力强和适应干旱等生物学特征, 而且比模式植物拟南芥(A.thaliana)更耐高盐胁迫。将前期克隆的小拟南芥锌指蛋白基因ApZFP通过花滴法转化到哥伦比亚生态型拟南芥(Col-0)中,获得了独立表达的转基因株系。表型观察发现, 过量表达ApZFP基因可促使拟南芥在长短日照下均提前开花。实时荧光定量PCR结果显示, 转基因拟南芥株系中, 光周期途径中的CO基因和年龄途径中的SPL基因表达上调; 春化、环境温度和自主途径中的FLC基因表达下调; 编码成花素的基因FT及下游开花相关基因AP1和LFY的表达量均升高。进一步通过盐、干旱和ABA胁迫处理ApZFP转基因株系的种子和幼苗, 发现在胁迫处理下, 与对照相比, 转基因拟南芥种子萌发率较高, 幼苗主根较长。因此推测, ApZFP在植物发育过程中具有多种功能, 可能既参与植物的开花转变过程, 又同其它植物的锌指蛋白基因一样, 参与植物的耐逆过程。     

用气相色谱测定植物样品中的微量细胞分裂素

细胞分裂素广泛地存在于植物组织和微生物中,对植物的细胞分裂、分化、种子的萌发和休眠等生长发育过程有调节功能。因此,在组织培养、植物细胞工程和开花植物及微生物的生长发育理论和应用技术研究中,都需要对植物体内的细胞分裂素进行测定。随着生物科学的发展,在现有测定细胞分裂素含量的方法中,生物试法准确度差,已不适于研究工作的     

Cytokinin Activity in Lupinus albus L: IV. Distribution in Seeds

Endogenous levels of cytokinin activity were examined in Lupinus albus L. seed at intervals of 2 weeks after anthesis using the soybean callus bioassay. High levels of cytokinin activity per gram seed material were present in the seeds at 2, 4, and 6 weeks after anthesis. The cytokinin activity per gram seed material was low at 8 and 10 weeks after anthesis. Cytokinin activity associated with each seed was greatest at 6 weeks after anthesis. The majority of the activity in the seeds at 4, 6, and 8 weeks after anthesis was in the endosperm. Cytokinin activity was also detected in the testas and embryos at 4, 6, 8, and 10 weeks, and the suspensors at 4 weeks. Column chromatography of extracts of the different seed fractions on Sephadex LH-20 indicated that the cytokinins present coeluted with zeatin, zeatin riboside, and the glucoside cytokinins. It is suggested that cytokinins are accumulated in the seeds and are stored in the endosperm mainly in the form of ribosides and glucosides of zeatin. The reduction in cytokinin activity in the seed coincides with the reduction in endosperm volume and embryo growth and suggests that these compounds are utilized during the course of seed maturation.     

Cytokinin receptor-dependent and receptor-independent pathways in the dehydration response of Arabidopsis thaliana

Cytokinin signaling in Arabidopsis thaliana utilizes a multi-step two-component signaling (TCS) system comprised of sensor histidine kinases (AHKs), histidine phosphotransfer proteins (AHPs), and response regulators (ARRs). Recent studies have suggested that the cytokinin TCS system is involved in a variety of other signaling and metabolic pathways. To further explore a potential function of the cytokinin TCS in the Arabidopsis dehydration stress response, we investigated the expression of all type-A ARR genes and a type-C ARR, ARR22, in both wild type and ahk single, double, and triple mutants in response to dehydration compared to cytokinin as well as dehydration tolerance of ahk mutants. We found that drought significantly induced the expression of a subset of ARR genes, ARR5, ARR7, ARR15, and ARR22. The results of expression analyses in ahk single, double, and triple mutants demonstrated that the cytokinin receptors AHK2 and AHK3 are redundantly involved in dehydration-inducible expression of ARR7, but not that of ARR5, ARR15, or ARR22. Dehydration tolerance assays showed that ahk2 and ahk3 single mutants exhibited enhanced dehydration tolerance compared with that of wild-type plants and ahk4 mutants, and that ahk2 ahk3 double mutants exhibited stronger drought tolerance than that of ahk3 ahk4, which exhibited more enhanced drought tolerance than that of wild-type plants and ahk single mutants. Taken together, these results demonstrate that while the cytokinin receptors AHK2 and AHK3 are critically involved in the dehydration tolerance response, both cytokinin receptor-dependent pathway and receptor-independent pathway occur in the dehydration response regulating ARR gene expression. In addition, preincubating ahk2, ahk3, ahk4, and the wild-type plants with cytokinin induced enhanced dehydration stress tolerance in these plants, demonstrating that cytokinins are involved in regulating plant response to dehydration stress.     

Cytokinin receptor antagonists derived from 6-benzylaminopurine

Recently we reported 6-(2-hydroxy-3-methylbenzylamino)purine (PI-55) as the first molecule to antagonize cytokinin activity at the receptor level. Here we report the synthesis and in vitro biological testing of eleven BAP derivatives substituted in the benzyl ring and in the C2, N7 and N9 positions of the purine moiety. The ability of the compounds to interact with Arabidopsis cytokinin receptors AHK3 and CRE1/AHK4 was tested in bacterial receptor and in live-cell binding assays, and in an Arabidopsis ARR5:GUS (Arabidopsis response regulator 5) reporter gene assay. Cytokinin activity of the compounds was determined in classical cytokinin biotests (tobacco callus, wheat leaf senescence and Amaranthus bioassays). 6-(2,5-Dihydroxybenzylamino)purine (LGR-991) was identified as a cytokinin receptor antagonist. At the molecular level LGR-991 blocks the cytokinin receptor CRE1/AHK4 with the same potency as PI-55. Moreover, LGR-991 acts as a competitive inhibitor of AHK3, and importantly shows reduced agonistic effects in comparison to PI-55 in the ARR5:GUS reporter gene assay and in cytokinin bioassays. LGR-991 causes more rapid germination of Arabidopsis seeds and increases hypocotyl length of dark-grown seedlings, which are characteristics of plants with a reduced cytokinin status. LGR-991 exhibits a structural motive that might lead to preparation of cytokinin antagonists with a broader specificity and reduced agonistic properties.     

Cytokinin affects circadian-clock oscillation in a phytochrome B- and Arabidopsis response regulator 4-dependent manner

In higher plants, many developmental processes, such as photomorphogenesis and flowering, are coregulated by light and the phytohormone cytokinin. Interactions between light and cytokinin pathways are presumably mediated by common signaling intermediates. However, the molecular mechanism of these interactions remains unclear. Here, we report that cytokinin specifically induces the expression of the Arabidopsis circadian oscillator genes LATE ELONGATED HYPOCOTYL ( LHY ) and CIRCADIAN CLOCK-ASSOCIATED 1 ( CCA1 ) but represses the expression of TIMING OF CAB EXPRESSION 1 in a light-dependent manner. Consistent with these observations, cytokinin causes a shifted phase of the circadian clock. Mutant studies showed that the altered clock oscillation modulated by cytokinin is dependent on phytochrome B ( PHYB ) and Arabidopsis RESPONSE REGULATOR 4 ( ARR4 ). Whereas overexpression of LHY or CCA1 renders plants slightly more sensitive to cytokinin, phyB and a lhy/cca1 double mutant are less sensitive to the hormone. These results suggest that cytokinin affects the circadian clock oscillation in a PHYB - and ARR4 -dependent manner and that cytokinin signaling is also regulated by light-signaling components, including PHYB , LHY and CCA1 . Therefore, phyB, ARR4 and the circadian oscillator may function as signaling intermediates to integrate light and cytokinin pathways.