OsSIZ1 Regulates the Vegetative Growth and Reproductive Development in Rice

SAP and MIZ (SIZ) is a small ubiquitin-related modifier (SUMO) E3 ligase that facilitates conjugation of SUMO to protein substrates. Although there have been a number of reports about the functions of SIZ1 in Arabidopsis in the regulation of diverse life processes, no information regarding the role of SIZ in other plants is available yet. In this work, two homologous genes from rice (Oryza sativa) were isolated and designated as OsSIZ1 and OsSIZ2 based on amino acid sequence homology to AtSIZ1 and their phylogenetic relationship. The function in the vegetative growth and reproductive development in rice was investigated using OsSIZ1 mutants containing a T-DNA insertion. The results showed that the mutant Ossiz1 exhibited the significant changes in several growth and developmental parameters, including primary root length, adventitious root number, plant height, leaf and panicle length, flower formation, and seed-setting rate compared with wild type. Taking together these results indicate that OsSIZ1 plays an important role in regulating growth and development in rice.     

The Sodium/Proton Exchanger NHE8 Regulates Late Endosomal Morphology and Function

The pH and lumenal environment of intracellular organelles is considered essential for protein sorting and trafficking through the cell. We provide the first evidence that a mammalian NHE sodium (potassium)/proton exchanger, NHE8, plays a key role in the control of protein trafficking and endosome morphology. At steady state, the majority of epitope-tagged NHE8 was found in the trans-Golgi network of HeLa M-cells, but a proportion was also localized to multivesicular bodies (MVBs). Depletion of NHE8 in HeLa M-cells with siRNA resulted in the perturbation of MVB protein sorting, as shown by an increase in epidermal growth factor degradation. Additionally, NHE8-depleted cells displayed striking perinuclear clustering of endosomes and lysosomes, and there was a ninefold increase in the cellular volume taken up by LAMP1/LBPA-positive, dense MVBs. Our data points to a role for the ion exchange activity of NHE8 being required to maintain endosome morphology, as overexpression of a nonfunctional point mutant protein (NHE8 E225Q) resulted in phenotypes similar to those seen after siRNA depletion of endogenous NHE8. Interestingly, we found that depletion of NHE8, despite its function as a sodium (potassium)/proton antiporter, did not affect the overall pH inside dense MVBs.     

TDIF Peptide Signaling Regulates Vascular Stem Cell Proliferation via the WOX4 Homeobox Gene in Arabidopsis

The indeterminate nature of plant growth and development depends on the stem cell system found in meristems. The Arabidopsis thaliana vascular meristem includes procambium and cambium. In these tissues, cell–cell signaling, mediated by a ligand-receptor pair made of the TDIF (for tracheary element differentiation inhibitory factor) peptide and the TDR/PXY (for TDIF RECEPTOR/ PHLOEM INTERCALATED WITH XYLEM) membrane protein kinase, promotes proliferation of procambial cells and suppresses their xylem differentiation. Here, we report that a WUSCHEL-related HOMEOBOX gene, WOX4, is a key target of the TDIF signaling pathway. WOX4 is expressed preferentially in the procambium and cambium, and its expression level was upregulated upon application of TDIF in a TDR-dependent manner. Genetic analyses showed that WOX4 is required for promoting the proliferation of procambial/cambial stem cells but not for repressing their commitment to xylem differentiation in response to the TDIF signal. Thus, at least two intracellular signaling pathways that diverge after TDIF recognition by TDR might regulate independently the behavior of vascular stem cells. Detailed observations in loss-of-function mutants revealed that TDIF-TDR-WOX4 signaling plays a crucial role in the maintenance of the vascular meristem organization during secondary growth.     

The Imprinted Gene PEG3 Inhibits Wnt Signaling and Regulates Glioma Growth

The imprinted gene PEG3 confers parenting and sexual behaviors, alters growth and development, and regulates apoptosis. However, a molecular mechanism that can account for the diverse functions of Peg3/Pw1 is not known. To elucidate Peg3-regulated pathways, we performed a functional screen in zebrafish. Enforced overexpression of PEG3 mRNA during zebrafish embryogenesis decreased β-catenin protein expression and inhibited Wnt-dependent tail development. Peg3/Pw1 also inhibited Wnt signaling in human cells by binding to β-catenin and promoting its degradation via a p53/Siah1-dependent, GSK3β-independent proteasomal pathway. The inhibition of the Wnt pathway by Peg3/Pw1 suggested a role in tumor suppression. Hypermethylation of the PEG3 promoter in primary human gliomas led to a loss of imprinting and decreased PEG3 mRNA expression that correlated with tumor grade. The decrease in Peg3/Pw1 protein expression increased β-catenin, promoted proliferation, and inhibited p53-dependent apoptosis in human CD133⁺ glioma stem cells. Thus, mammalian imprinting utilizes Peg3/Pw1 to co-opt the Wnt pathway, thereby regulating development and glioma growth.     

An RNA Transport System in Candida albicans Regulates Hyphal Morphology and Invasive Growth

Localization of specific mRNAs is an important mechanism through which cells achieve polarity and direct asymmetric growth. Based on a framework established in Saccharomyces cerevisiae, we describe a She3-dependent RNA transport system in Candida albicans, a fungal pathogen of humans that grows as both budding (yeast) and filamentous (hyphal and pseudohyphal) forms. We identify a set of 40 mRNAs that are selectively transported to the buds of yeast-form cells and to the tips of hyphae, and we show that many of the genes encoded by these mRNAs contribute to hyphal development, as does the transport system itself. Although the basic system of mRNA transport is conserved between S. cerevisiae and C. albicans, we find that the cargo mRNAs have diverged considerably, implying that specific mRNAs can easily move in and out of transport control over evolutionary timescales. The differences in mRNA cargos likely reflect the distinct selective pressures acting on the two species.     

番茄灰霉病生防融合子基因组DNA提取方法的研究

以番茄灰霉病生防菌株木霉T-23和链霉菌A的融合子为实验材料,在SDS-CrAB法、改进CTAB法和氯化苄法的基础上加以改进,比较和研究了真菌融合子基因组DNA的提取,找到了一种快速、高效的基因组DNA提取方法,为进一步对融合子进行生防机制和分子生物学水平的研究提供基础。结果表明SDS-CTAB法提取的基因组DNA OD_(260)/OD_(280)为1．909,DNA浓度约为42．0ng/μL,可以满足分子生物学实验的需要。并将提取的基因组DNA直接用于PCR扩增,得到了多态性的RAPD图谱。     

The FgNot3 Subunit of the Ccr4-Not Complex Regulates Vegetative Growth,Sporulation, and Virulence in Fusarium graminearum

The Ccr4-Not complex is evolutionarily conserved and important for multiple cellular functions in eukaryotic cells. In this study, the biological roles of the FgNot3 subunit of this complex were investigated in the plant pathogenic fungus Fusarium graminearum. Deletion of FgNOT3 resulted in retarded vegetative growth, retarded spore germination, swollen hyphae, and hyper-branching. The ΔFgnot3 mutants also showed impaired sexual and asexual sporulation, decreased virulence, and reduced expression of genes related to conidiogenesis. Fgnot3 deletion mutants were sensitive to thermal stress, whereas NOT3 orthologs in other model eukaryotes are known to be required for cell wall integrity. We found that FgNot3 functions as a negative regulator of the production of secondary metabolites, including trichothecenes and zearalenone. Further functional characterization of other components of the Not module of the Ccr4-Not complex demonstrated that the module is conserved. Each subunit primarily functions within the context of a complex and might have distinct roles outside of the complex in F. graminearum. This is the first study to functionally characterize the Not module in filamentous fungi and provides novel insights into signal transduction pathways in fungal development.     

The Homeobox Gene GLABRA2 Affects Seed Oil Content in Arabidopsis

Despite a good understanding of genes involved in oil biosynthesis in seed, the mechanism(s) that controls oil accumulation is still not known. To identify genes that control oil accumulation in seed, we have developed a simple screening method to isolate Arabidopsis seed oil mutants. The method includes an initial screen for seed density followed by a seed oil screen using an automated Nuclear Magnetic Resonance (NMR). Using this method, we isolated ten low oil mutants and one high oil mutant. The high oil mutant, p777, accumulated 8% more oil in seed than did wild type, but it showed no differences in seed size, plant growth or development. The high-oil phenotype is caused by the disruption of the GLABRA2 gene, a previously identified gene that encodes a homeobox protein required for normal trichome and root hair development. Knockout of GLABRA2 did not affect LEAFY COTYLEDON 1 and PICKLE expression in developing embryo. The result indicates that in addition to its known function in trichome and root hair development, GLABRA2 is involved in the control of seed oil accumulation.     

拟南芥漆酶基因AtLAC2调控植物生长发育的研究

拟南芥漆酶基因家族有17个成员,但其功能还不清楚。本文采用过量表达的方法初步分析了拟南芥漆酶基因AtLAC2的功能。GUS染色显示AtLAC2在拟南芥不同生长发育时期的多个组织和器官中都有较强的表达,且在叶片和茎尖中的表达最强。AtLAC2的过量表达植株开花时间推迟,花序轴分枝变多,叶片变小。以上结果表明AtLAC2基因在调控植物生长发育中具有重要作用。     

EMF基因与植物营养生长

在高等植物中,外源和内源因素共同调控着植物从营养生长到生殖生长的转换。拟南芥EMF1和EMF2基因缺失的突变体不经过任何营养生长,种子萌发后便开花,这说明EMF基因是植物花发育的抑制基因。目前已从水稻、玉米、拟南芥等植物中克隆得到EMF同源基因,但其功能研究大多停留在拟南芥上。研究表明,EMF基因决定着植物营养生长阶段的发育,抑制植物开花。因此,开展EMF基因的分离、克隆和功能研究,有利于阐述植物营养生长过程阶段的抑花机制。对EMF基因的研究进展进行了综述,并提出EMF基因表达调控的闸门模型,以对EMF基因功能的进一步分析提供参考。     

拟南芥漆酶基因AtLAC4参与生长及非生物胁迫响应

植物漆酶基因家族在拟南芥(Arabidopsis thaliana)中共有17个成员,目前各基因的具体功能尚不十分清楚.该研究利用过量表达的方法初步分析了拟南芥AtLAC4的功能.GUS染色显示AtLAC4在拟南芥的维管组织中有较强的表达,并在叶片排水器中特异表达.AtLAC4过量表达导致植株木质素含量增多、次生壁加厚、植株变小和莲座叶叶柄变短.ABA对AtLAC4的表达具有明显的诱导作用,AtLAC4过量表达植株对外源ABA敏感;干旱处理后,AtLAC4过量表达植株的耐旱能力比野生型明显增强.以上结果表明,AtLAC4基因在调控植物生长发育及非生物胁迫响应中具有重要作用.     

Fruit Regulates Bud Sprouting and Vegetative Growth in Field-Grown Loquat Trees (Eriobotrya japonica Lindl.): Nutritional and Hormonal Changes

The effects of fruit on bud sprouting and vegetative growth were compared on fruiting and defruited loquat trees from fruit set onward. Carbohydrate and nitrogen content in leaves and bark tissues and hormone concentrations were studied during the fruit development and vegetative growth periods. On defruited trees, a significant proportion of buds sprouted in winter, whereas buds from fruiting trees sprouted only in the spring when fruit reached its final size. Furthermore, when panicles were completely removed in autumn, the buds also sprouted. In addition, fruit directly affected vegetative growth by reducing shoot length. An effect of sink removal (flower or fruit) promoting bud sprouting, regardless of the season, was then demonstrated. Neither soluble sugar concentration nor nitrogen fraction concentration in leaves or bark tissues was related to bud sprouting, but a certain nutritional imbalance was observed during the most active period of fruit development. Moreover, fruit sink activity significantly modified hormone content by increasing indole-3-acetic acid (IAA) and reducing zeatin concentrations, resulting in a higher IAA/zeatin ratio parallel to the lower bud sprouting intensity. Therefore, these changes caused by fruit removal are all related to vegetative growth, but there is no evidence that they are responsible for bud burst.     

Vegetative Plant Growth Analysis in Controlled Environments

Current techniques for analysing growth are compared using datafrom young plants grown in artificially-lit growth cabinets.A statistical method of fitting curves to log dry weight andlog leaf areas led to values which often diverged from biologicalexpectation. It was more satisfactory to make the calculationsassuming that a quadratic relation always applied. It appears that the statistical methods cannot be used unmodifiedfor experiments involving comparisons between artificially-litcabinets. Cabinet environments are seldom replicated and thereforethe consequences of isolated anomalies in either the environmentor in a particular harvest are not allowed for and are reproducedin the final curves. In addition the statistical method assumesthat all the growth curves are entirely independent, whereasthere is a tendency for the opposite to be true.