Preferential translocation of boron to young leaves in Arabidopsis thaliana Regulated by the BOR1 Gene

A mutant of Arabidopsis thaliana, bor1-1 (Noguchi et al. 1997: Plant Physiol., 115, 901–916) requires high levels of boron (B) for normal growth. We analyzed the B-deficiency symptoms of bor1-1 mutant plants in detail. A low B supply retarded the growth of the mutant plants more evidently in leaves than in roots. In particular, cell expansion and formation of air spaces were severely impaired by B deficiency in young rosette leaves. Such defects in growth were correlated with the reduced contents of B in leaves. These defects were not observed when a sufficient amount of B was supplied. Uptake experiments with ¹⁰B-enriched tracer B demonstrated that B taken up through roots was preferentially transported to young leaves compared to old leaves in the wild-type plants under a low B supply. Such a preferential transport to young leaves was not evident in the mutant plants. In conclusion, our data demonstrated that in A. thaliana plants B is preferentially transported to young organs under a low B supply and that this transport process is controlled at least in part by the BOR1 gene.     

Increased supply of boron to swiss chard plants did not affect the level of boron in a cell wall-bound form: A possible application to the diagnosis of nutrition of plants

Swiss chard plants were water-cultured under various B levels ranging from 0.01 to 20 g B m^-3 culture solutions for 4 weeks. The B content of the shoot increased with the increase in the B supply. The increase, however, was entirely ascribed to acetate buffer (20 mol m^-3 pH 4.0)-soluble B, and the content of acetate buffer-insoluble, cell wall-bound B did not increase.. More than ca. 80% of the cell wall-bound B was associated with rhamnogalacturonan II under various B levels. The amount of acetate buffer-soluble B could be estimated from the B levels in the expressed leaf sap.     

Boron deprivation immediately causes cell death in growing roots of Arabidopsis thaliana (L.) Heynh.

Boron (B) is essential for the correct formation of cell wall structure because it is a component of borate-ester cross-links in pectin. Previously, we showed that removal of B from the culture medium immediately induced stress responses in suspension-cultured tobacco (Nicotiana tabacum L.) cells, but the mechanism by which cells exhibit such rapid responses remained unclear. In this study, we characterized the early responses of Arabidopsis thaliana (L.) Heynh. to B deprivation. Deprivation of B for 1 h caused cell death specifically in the root elongation zone. Reactive oxygen species accumulated in the same region, suggesting that the death was caused by oxidative damage. The B-deprivation treatment also induced the expressions of stress-responsive genes within 1 h. These results demonstrated that A. thaliana immediately senses and responds to the removal of B from the external medium. Similar responses were induced by calcium deprivation but not magnesium or potassium deprivation, suggesting that the failure of cross-linking in pectin molecules in growing cells triggers these rapid responses.     

拟南芥AtHEMA1基因的克隆及其表达载体的构建

为探究AtHEMA1基因转化植物后对叶绿素合成机制的影响,本实验设计特异引物,以拟南芥基因组DNA为模板,采用PrimStar HS DNA聚合酶扩增AtHEMA1基因。将AtHEMA1基因克隆至载体pVCT2101,获得植物表达载体pVCT2298。     

水稻OsNPR1基因RNA干涉载体的构建及其对水稻的转化

拟南芥NPR1基因是拟南芥中系统获得抗性的正调节基因.为鉴定水稻中的一个与拟南芥NPR1基因同源的基因OsNPR1的功能,用PCR扩增的该基因cDNA的667～1088核苷酸,构建了一个以OsNPR1为靶基因的RNA干涉水稻表达载体pONPR422-I,并用根癌农杆菌介导法转化水稻桂99,共获得了6株潮霉素抗性的再生苗.Southern杂交证实,这些再生苗均为转基因植株,能生长、结实,为进一步鉴定该基因功能奠定了基础.     

水稻HTD1基因启动子在转基因拟南芥中的表达特征

通过分析β-葡萄糖醛酸苷酶(β-glucuronidase, GUS）基因产物,对水稻HIGH-TILLERING DWARF1(HTD1)基因启动子在转基因拟南芥中的表达特性进行初步研究。用已构建的含HTD1基因启动子和GUS报告基因的植物表达载体,通过农杆菌介导转化拟南芥,对转基因拟南芥进行GUS组织化学染色,观察该启动子的表达特性。结果表明,在HTD1基因启动子的驱动下,GUS报告基因主要在转基因拟南芥幼苗期的叶片、叶柄、下胚轴以及主根基部的维管组织中表达。     

花粉管通道法介导的真菌耐盐基因转化拟南芥

橡胶树内生真菌ITBB2-1具有很强的抗盐性,在培养基中添加2倍海水盐度的NaCl能显著促进菌落的生长。采用两种方法研究利用花粉管通道法将ITBB2-1耐盐基因导入拟南芥。多数耐盐转基因植株畸形,生长发育不正常。通过对一千两百余株转基因植株的筛选,获得了耐盐性显著提高、生长发育正常的转基因植株3个。对主要农艺性状统计分析发现,转基因植株叶片的长度、宽度和面积均比野生型植株小,差异达极显著水平。转基因植株SR3的角果长度仅为野生型的64．5％,SR1和SR2的角果长度与野生型无显著差异。本研究表明,在真菌耐盐机制尚未得到研究和耐盐基因尚未克隆的情况下,可以采用花粉管通道法将其耐盐特性导入高等植物中。     

水杨酸在赭曲霉毒素A诱导的拟南芥毒性中的作用

赭曲霉毒素A(ochratoxin A,OTA)是一种分布广泛的真菌毒素,会对谷物、动物饲料、动物性食品等造成污染。OTA对多种动物具有较强的肾毒性和肝毒性,并有致畸、致突变和致癌作用。对植物的研究表明,OTA还具有植物毒性。本实验研究了植物中重要的内源信号分子水杨酸(Salicyli cacid,SA)在OTA对拟南芥(Arabidopsis thaliana)毒性中的作用。利用高效液相色谱测定了拟南芥叶片在OTA处理下SA含量的变化,结果显示,OTA胁迫促进了SA含量的上升;通过实时荧光定量PCR测定了OTA对SA途径中重要的病程相关蛋白1基因(pathogenesis-related gene1,PR1)相对表达量的影响,结果显示,OTA能诱导PR1的表达,并且这种诱导作用与OTA胁迫时间有关;SA与OTA同时处理拟南芥叶片后,观察到SA能造成OTA引起的叶片坏死斑的加重,相对电导率和活性氧含量的测定结果表明,SA能加重OTA对叶片的伤害,促进OTA诱导的活性氧的上升。本研究表明,SA参与了OTA诱导的拟南芥毒性过程,SA和OTA共同处理能增强OTA的植物毒性。     

植物LFY基因的研究进展

LFY基因在植物花分生组织形成中处于关键位置,维持花分生组织的正常功能、花启动,防止花分生组织的逆转。LFY基因需要其他成花基因相互作用,构成一个基因调控网络,其中任一基因的失活,其功能都会被其他基因部分补偿。LFY基因的表达除受碳源、植物激素等因子影响外,还受其他诸多因素的影响。文章就国内外对LFY基因及其同源基因的一些研究进展进行了综述,重点介绍了该基因在植物花发育中的功能、表达及其影响因子,同时展望其应用前景。     

葡萄NAC转录因子家族生物信息学分析

NAC基因家族是植物所特有的一类重要转录因子,广泛参与植物生长、发育以及器官建成、逆境胁迫应答等反应。目前,基因组信息的挖掘和分析已经成为葡萄功能基因组学研究的重要组成部分。本文利用生物信息学方法对葡萄143条NAC蛋白序列的系统发生和NAC基因组定位进行分析,然后对其氨基酸组成成分、理化性质以及二级和三级结构进行预测和分析,同时还分析了葡萄与拟南芥的NAC基因家族之间的联系。结果显示这143条蛋白序列与拟南芥94个NAC基因蛋白序列一起分成了16个亚族,说明拟南芥与葡萄NAC基因间具有较高的保守性。基因组定位结果发现143条NAC基因分布在17条染色体上。研究还发现不同亚家族间氨基酸数目、氨基酸序列间的疏水性存在一定的差异;而它们的二级结构都主要以随机卷曲为组成部分,且143条氨基酸序列三维结构十分相似。本文试验结果将为葡萄NAC基因家族的进一步功能分析提供重要研究基础。     

八棱海棠MdPPO2B基因的克隆及降解苯酚研究

为了探索果树对酚类化合物的修复潜力,从八棱海棠中克隆获得多酚氧化酶基因Md PPO2B,并构建该基因植物超量表达载体,通过转化模式植物拟南芥研究该基因对酚类化合物的修复功能。结果表明,在平板、盆栽、液体3种试验中,不加入苯酚,转基因植株在生长状态和外部形态上和野生型相似;当苯酚浓度分别为0.1 m M和1 m M时,通过植物的根长、叶片鲜重等比较发现,转基因株系比野生型植株对苯酚的耐受性更强,其生长形态较为正常,而野生型植株的生长则受到了明显抑制。由此可见,Md PPO2B转基因植物的PPO活性在植物降解酚类化合物过程中起重要作用;使用果树来源的多酚氧化酶基因用于有机污染物修复,对环境治理具有较好的应用前景。     

葡萄SBP基因家族生物信息学分析

SBP（squamosa promoter binding protein,SBP）基因家族是植物所特有的一类重要转录因子,广泛参与植物生长、发育以及多种生理生化反应的信号传导。葡萄是继拟南芥、水稻和杨树之后完成全基因组测序的第四种开花植物,因此葡萄逐渐成为分子生物学研究的重点对象,进行葡萄基因组信息挖掘与分析对于葡萄功能基因组学的发展具有重要意义。本文利用生物信息学方法对葡萄家族45条SBP蛋白序列的系统发生和SBP基因组定位进行分析,然后对其氨基酸组成成分、理化性质以及二级和三级结构进行预测和分析,同时还分析了葡萄与拟南芥的SBP基因家族之间的联系。结果显示这45条蛋白序列与拟南芥16个SBP基因蛋白序列一起分成了3个亚族,说明拟南芥与葡萄SBP基因间具有较高的保守性;进一步的基因组定位结果发现其分布在14条染色体上,较拟南芥在染色体上的分布更为分散。研究还发现不同亚家族间氨基酸数目、氨基酸序列间的疏水性存在一定的差异;而二级结构预测结果发现,41条氨基酸序列以随机卷曲为主要组成部分,这与拟南芥相似,且45条氨基酸序列三维结构十分相似。本文实验结果均为葡萄SBP基因家族的进一步功能分析提供了重要研究基础。     

URANIUM INDUCED EFFECTS ON DEVELOPMENT AND MINERAL NUTRITION OF ARABIDOPSIS THALIANA

This study aimed to investigate effects on growth and development and alterations in the nutrient profiles for Arabidopsis thaliana seedlings following uranium exposure. Seventeen-day-old Arabidopsis thaliana seedlings, grown in hydroponics, were exposed to 0, 0.1, 1, 10 and 100 μM uranium for one, three and seven days. Fresh weight of leaves and roots decreased after exposure to 100 μM uranium for one and three days and after exposure to 1, 10 and 100 μM uranium for seven days. Anthocyanous-colored leaves and stunted yellow roots were observed after exposure to 100 μM uranium. The uranium content of the roots highly increased but the root-to-shoot transfer of uranium was limited. Uranium exposure resulted in disturbed macro- and micronutrient profiles, especially following exposure to 100 μM. This study indicates that elevated uranium concentrations can cause important morphological and physiological effects and disturb the nutrient profiles in Arabidopsis thaliana seedlings.