Heterologous Expression of the Wheat Aquaporin Gene TaTIP2;2 Compromises the Abiotic Stress Tolerance of Arabidopsis thaliana

Aquaporins are channel proteins which transport water across cell membranes. We show that the bread wheat aquaporin gene TaTIP2;2 maps to the long arm of chromosome 7b and that its product localizes to the endomembrane system. The gene is expressed constitutively in both the root and the leaf, and is down-regulated by salinity and drought stress. Salinity stress induced an increased level of C-methylation within the CNG trinucleotides in the TaTIP2;2 promoter region. The heterologous expression of TaTIP2;2 in Arabidopsis thaliana compromised its drought and salinity tolerance, suggesting that TaTIP2;2 may be a negative regulator of abiotic stress. The proline content of transgenic A. thaliana plants fell, consistent with the down-regulation of P5CS1, while the expression of SOS1, SOS2, SOS3, CBF3 and DREB2A, which are all stress tolerance-related genes acting in an ABA-independent fashion, was also down-regulated. The supply of exogenous ABA had little effect either on TaTIP2;2 expression in wheat or on the phenotype of transgenic A. thaliana. The expression level of the ABA signalling genes ABI1, ABI2 and ABF3 remained unaltered in the transgenic A. thaliana plants. Thus TaTIP2;2 probably regulates the response to stress via an ABA-independent pathway(s).     

The R2R3-MYB gene family in Arabidopsis thaliana

MYB factors represent a family of proteins that include the conserved MYB DNA-binding domain. In contrast to animals, plants contain a MYB-protein subfamily that is characterised by the R2R3-type MYB domain. 'Classical' MYB factors, which are related to c-Myb, seem to be involved in the control of the cell cycle in animals, plants and other higher eukaryotes. Systematic screens for knockout mutations in MYB genes, followed by phenotypic analyses and the dissection of mutants with interesting phenotypes, have started to unravel the functions of the 125 R2R3-MYB genes in Arabidopsis thaliana. R2R3-type MYB genes control many aspects of plant secondary metabolism, as well as the identity and fate of plant cells.     

丹参体内Sm-miR858对R2R3-MYB转录因子SmPAP1进行靶向负调控作用研究

MicroRNAs(miRNAs)是一类对基因表达进行负调控的非编码小分子RNA。通过前期对丹参miRNAs的高通量测序得到了一个miR858成熟序列,命名为Sm-miR858。序列比对显示,Sm-miR858与其它植物中已鉴定的miR858序列高度保守;Small RNA Northern blotting结果显示Sm-miR858在丹参根、茎和叶组织中均有表达,叶中表达水平相对较高。为了探究Sm-miR858在丹参体内的功能,首先利用在线生物软件对Sm-miR858的靶标基因进行预测,psRNATarget分析结果显示,Sm-miR858的潜在靶标基因共有13个,其中一个靶标基因SmPAP1作为一个重要的转录因子参与丹参酚酸类活性物质的代谢调控。为了验证Sm-miR858对SmPAP1的靶向作用,采用Real-time quantitative PCR依次对烟草瞬时表达体系和丹参组织器官中的Sm-miR858与SmPAP1之间共表达相关性进行分析与实验验证。Real-time qPCR结果显示,在丹参组织中SmPAP1与Sm-miR858共表达水平存在显著的负相关性。进而分别构建Sm-miR858和SmPAP1过表达植物载体,并在烟草叶片中进行瞬时共表达研究。结果显示,与对照相比,Sm-miR858过表达会导致SmPAP1的mRNA水平显著下降,说明在丹参体内Sm-miR858的确对SmPAP1基因表达进行靶向负调控。研究结果为阐明Sm-miR858在丹参体内酚酸类活性物质代谢途径调控作用奠定坚实的基础。     

辣椒R2R3-MYB转录因子家族的全基因组鉴定与比较进化分析

MYB转录因子作为植物中最大的转录因子家族之一,参与植物的生长、代谢、抵御生物和非生物胁迫等多种生理生化过程。R2R3-MYB是MYB转录因子家族的主要存在形式。辣椒是具有重要经济价值的蔬菜作物,其R2R3-MYB转录因子缺乏系统的研究。从一年生辣椒(Capsicum annuum)、浆果状辣椒(C. baccatum...     

小麦R2R3-MYB转录因子TaMYB3-4D的克隆及功能分析

MYB转录因子是植物最大的转录因子家族之一,广泛参与植物各种生理生化过程。该研究通过对小麦基因组测序数据库进行同源搜索,利用电子克隆技术从紫色籽粒小麦品种‘高原115’中分离得到了一个新的MYB基因TaMYB3-4 D。结果表明,TaMYB3-4D仅含有一个内含子,其编码蛋白含有2个连续的MYB结构域,为典型的R2R3-MYB蛋白。TaMYB3-4D系统发生关系上与调控花青素合成的MYB基因亲缘关系较近。TaMYB3-4 D与bHLH基因ZmR瞬时表达能够诱导白色胚芽鞘中花青素的合成。此外,TaMYB3-4 D基因仅在‘高原115’含花青素的种皮和胚芽鞘中表达,在根、茎、叶中均未表达。研究表明,TaMYB3-4 D基因是一个具有调控花青素合成代谢功能的R2R3-MYB基因,很有可能参与小麦花青素的生物合成。     

The DNA Replication Factor RFC1 Is Required for Interference-Sensitive Meiotic Crossovers in Arabidopsis thaliana

During meiotic recombination, induced double-strand breaks (DSBs) are processed into crossovers (COs) and non-COs (NCO); the former are required for proper chromosome segregation and fertility. DNA synthesis is essential in current models of meiotic recombination pathways and includes only leading strand DNA synthesis, but few genes crucial for DNA synthesis have been tested genetically for their functions in meiosis. Furthermore, lagging strand synthesis has been assumed to be unnecessary. Here we show that the Arabidopsis thaliana DNA REPLICATION FACTOR C1 (RFC1) important for lagging strand synthesis is necessary for fertility, meiotic bivalent formation, and homolog segregation. Loss of meiotic RFC1 function caused abnormal meiotic chromosome association and other cytological defects; genetic analyses with other meiotic mutations indicate that RFC1 acts in the MSH4-dependent interference-sensitive pathway for CO formation. In a rfc1 mutant, residual pollen viability is MUS81-dependent and COs exhibit essentially no interference, indicating that these COs form via the MUS81-dependent interference-insensitive pathway. We hypothesize that lagging strand DNA synthesis is important for the formation of double Holliday junctions, but not alternative recombination intermediates. That RFC1 is found in divergent eukaryotes suggests a previously unrecognized and highly conserved role for DNA synthesis in discriminating between recombination pathways.