The trafficking protein SYP121 of Arabidopsis connects programmed stomatal closure and K⁺ channel activity with vegetative growth

The vesicle‐trafficking protein SYP121 (SYR1/PEN1) was originally identified in association with ion channel control at the plasma membrane of stomatal guard cells, although stomata of the Arabidopsis syp121 loss‐of‐function mutant close normally in ABA and high Ca²⁺. We have now uncovered a set of stomatal phenotypes in the syp121 mutant that reduce CO₂ assimilation, slow vegetative growth and increase water use efficiency in the whole plant, conditional upon high light intensities and low relative humidity. Stomatal opening and the rise in stomatal transpiration of the mutant was delayed in the light and following Ca²⁺‐evoked closure, consistent with a constitutive form of so‐called programmed stomatal closure. Delayed reopening was observed in the syp121, but not in the syp122 mutant lacking the homologous gene product; the delay was rescued by complementation with wild‐type SYP121 and was phenocopied in wild‐type plants in the presence of the vesicle‐trafficking inhibitor Brefeldin A. K⁺ channel current that normally mediates K⁺ uptake for stomatal opening was suppressed in the syp121 mutant and, following closure, its recovery was slowed compared to guard cells of wild‐type plants. Evoked stomatal closure was accompanied by internalisation of GFP‐tagged KAT1 K⁺ channels in both wild‐type and syp121 mutant guard cells, but their subsequently recycling was slowed in the mutant. Our findings indicate that SYP121 facilitates stomatal reopening and they suggest that K⁺ channel traffic and recycling to the plasma membrane underpins the stress memory phenomenon of programmed closure in stomata. Additionally, they underline the significance of vesicle traffic for whole‐plant water use and biomass production, tying SYP121 function to guard cell membrane transport and stomatal control.     

The G protein coupled receptor 3 is involved in cAMP and cGMP signaling and maintenance of meiotic arrest in porcine oocytes

The arrest of meiotic prophase in mammalian oocytes within fully grown follicles is dependent on cyclic adenosine monophosphate (cAMP) regulation. A large part of cAMP is produced by the Gs-linked G-protein-coupled receptor (GPR) pathway. In the present study, we examined whether GPR3 is involved in the maintenance of meiotic arrest in porcine oocytes. Expression and distribution of GPR3 were examined by western blot and immunofluorescence microscopy, respectively. The results showed that GPR3 was expressed at various stages during porcine oocyte maturation. At the germinal vesicle (GV) stage, GPR3 displayed a maximal expression level, and its expression remained stable from pro-metaphase I (MI) to metaphase II (MII). Immunofluorescence staining showed that GPR3 was mainly distributed at the nuclear envelope during the GV stage and localized to the plasma membrane at pro-MI, MI and MII stages. RNA interference (RNAi) was used to knock down the GPR3 expression within oocytes. Injection of small interfering double-stranded RNA (siRNA) targeting GPR3 stimulated meiotic resumption of oocytes. On the other hand, overexpression of GPR3 inhibited meiotic maturation of porcine oocytes, which was caused by increase of cGMP and cAMP levels and inhibition of cyclin B accumulation. Furthermore, incubation of porcine oocytes with the GPR3 ligand sphingosylphosphorylcholine (SPC) inhibited oocyte maturation. We propose that GPR3 is required for maintenance of meiotic arrest in porcine oocytes through pathways involved in the regulation of cAMP and cGMP.     

POPULATION QUANTITATIVE CHARACTERISTICS AND DYNAMICS OF RARE AND ENDANGERED TSUGA TCHEKIANGENSIS IN JIULONGSHAN NATURE RESERVE OF CHINA

 针对九龙山国家级自然保护区南方铁杉(Tsuga tchekiangensis)种群的分布特点, 设置了10个具有代表性的样地。以种群生命表及生存分析理论为基础, 编制了南方铁杉种群的静态生命表, 绘制了存活曲线、死亡率曲线、消失率曲线、生存率曲线、累计死亡率曲线、种群死亡密度曲线和危险率曲线, 分析了种群数量特征; 同时结合谱分析方法, 分析了南方铁杉种群数量的动态变化。结果表明: 1) 南方铁杉种群结构存在波动性, 幼年阶段的个体较丰富, 成年个体数量相对较少, 种群趋于Deevey Ⅱ型。2) 南方铁杉种群死亡率和消失率曲线变化趋势基本一致, 均出现两个高峰, 一个出现在第5龄级阶段, 另一个出现在第15龄级阶段。3) 南方铁杉种群的生存率单调下降, 累计死亡率单调上升, 生存率下降趋势前期高于后期, 累计死亡率则相反。4) 4个生存函数曲线表明, 南方铁杉具有前期稳定、中期锐减和后期衰退的特点。5) 种群动态的谱分析显示, 南方铁杉种群动态除受基波影响外, 还存在着明显的小周期波动, 谐波A3处周期的波动与南方铁杉的高生长有关; A6处周期的波动与外界环境变化有关; A8处周期的波动与南方铁杉进入生理衰退期有关。     

外源中心体在哺乳动物胚胎发育中的遗传机制

中心体是一个非膜包被的半保留细胞器,由一对相互垂直的圆柱形中心粒及其周围大量的高电子密度的蛋白质-中心体基质(pericentriolar material,PCM)组成.在所有哺乳动物细胞中,中心体(centrosome)作为主要的微管组织中心(microtubule organizing centers,MTOCs),起到组装和稳定微管的关键功能.在大多数哺乳动物精子形成过程中,精子保留了近端中心粒,失去了大部分的中心体旁蛋白和远端中心粒,而在卵母细胞形成过程中两个中心粒被逐渐降解,主要的中心体旁蛋白被保留了下来,弥散于卵胞质中.受精后,在卵母细胞中精子中心粒被进一步降解,来源于卵母细胞和精子的中心体旁蛋白形成受精卵的MTOCs在胚胎分裂过程中行使功能.但在小鼠等啮齿类动物精子形成过程中,两个中心粒全部被降解,因此受精卵中的MTOCs主要由来源于卵母细胞中心体旁蛋白组成.在大多数哺乳动物核移植胚胎中.外源中心粒在胚胎1-细胞期即被降解,而是来源于供体细胞和受体卵母细胞的中心体旁蛋白形成重构胚的MTOCs指导纺锤体形成,中心粒是在囊胚期才从头合成的.在灵长类中,来源于精子的中心粒能与PCM一起组成典型的中心体在胚胎分裂过程中行使功能,但在其核移植胚胎中,体细胞中心体和去核卵母细胞中剩余的中心体旁蛋白不能有效的组装形成功能性中心体,这可能是灵长类哺乳动物体细胞克隆失败的一个关键原因. 成过程中,两个中心粒全部被降解,因此受精卵中的MTOCs主要由来源于卵母细胞中心体旁蛋白组成.在大多数哺乳动物核移植胚胎中.外源中心粒在胚胎1-细胞期即被降解,而是来源于供体细胞和受体卵母细胞的中心体旁蛋白形成重构胚的MTOCs指导纺锤体形成,中心粒是在囊胚期才从头合成的.在灵长类中,来源于精子的中心粒能与PCM一起组成典型的中心 在胚胎分裂过程中行使功能,但在其核移植胚胎中,体细胞中心体和去核卵母细胞中剩余的中心体旁蛋白不能有效的组装形成功能性中心体,这可能是灵长类哺乳动物体细胞克隆失败的一个关键原因. 成过程中,两个中心粒全部被降解,因此受精卵中的MTOCs主要由来源于卵母细胞中心体旁蛋白组成.在大多数哺乳动物核移植胚胎中.外源中心粒在胚胎1-细胞期即被降解,而是来源于供体细胞和受体卵母细胞的中心体旁蛋白形成重构胚的MTOCs指导纺锤体形成,中心粒是在囊胚期才从头合成的.在灵长类中,来源于精子的中心粒能与PCM一起组成典型的中心 在胚胎分裂过程中行使功能,但在其核移植胚胎中,体细胞中心体和去核卵母细胞中剩余的中心体旁蛋白不能有效的组     

Forced Unfolding of Apocytochrome <Emphasis Type="Italic">b</Emphasis><Subscript>5</Subscript> by Steered Molecular Dynamics Simulation

Apocytochrome b5 (apocyt b5), a small b-type cytochrome with heme prosthetic group removal, has been subjected to steered molecular dynamics (SMD) simulations for investigating the consequences of mechanical force-induced unfolding. Both constant velocity (0.5 and 1.0 A/ps) and constant force (500, 750 and 1000 pN) stretching have been employed to model forced unfolding of apocyt b5. The results of SMD simulations elucidate that apocyt b5 is protected against external stress mainly through the interstrand hydrogen bonding between its beta1-beta2 and beta2-beta3 strands, highlighting the importance of hydrophobic core 2 in stabilization of apocyt b5. The existence of intermediate states manifested by current simulations in the forced unfolding pathway of apocyt b5 is different from the observations in pervious thermal or chemical unfolding studies in the absence of force. The present study could thus provide insights into the relationship between the two cooperative functional modules of apocyt b5 and also guide the rational molecular design of heme proteins.     

水分胁迫对入侵植物薇甘菊幼苗生长的影响

水分是影响薇甘菊(Mikania micrantha)生长的重要环境因子,但通过调控生长环境包括土壤水分和空气湿度来探讨这一入侵植物的适应能力的报道较少.本文通过设置2个水分梯度:处理Ⅰ土壤含水量30%～60%和空气相对湿度80%～90%,处理Ⅱ土壤含水量10%～20%和空气相对湿度20%～30%进行试验.结果发现土壤含水量在10%～20%且空气相对湿度在20%～30%时,水分胁迫能显著影响薇甘菊的幼苗生长和光合特性.胁迫条件下植株生长速率明显降低,最大净光合速率和最大量子效率分别是1.94 μmol·m-2·s-1和64.91 mmol·mol-1,比对照8.63 μmol·m-2·s-1和211.34 mmol·mol-1明显偏低.本文将空气相对湿度作为水分胁迫条件之一,阐述了空气相对湿度的增加能扩大薇甘菊的适生范围,并分析得出气孔限制可能是水分胁迫下薇甘菊生长受抑制的主要原因.     

水稻抗稻瘟病基因的标记辅助选择及定位克隆

水稻抗稻瘟病基因-稻瘟病菌无毒基因相互作用体系是当今植物分子病理学和抗病育种学研究领域的模式体系之一,其中抗病基因的分子定位与克隆及其标记辅助选择已成为该体系的重要内容。本文就这方面的研究进展作一简要综述,以期为水稻抗病育种提供有益的信息。     

拟南芥MT-II过量表达提高抗旱性(英文)

富含巯基的植物II型金属硫蛋白(MT)对植物抵抗重金属胁迫具有重要作用,其中一个可能机制是金属硫蛋白可能猝灭重金属引起的氧化胁迫。利用转MT-II基因和野生型拟南芥(Arabidopsis thaliana)植株来对比研究MT在胁迫过程中通过清除氧自由基,特别是H2O2而对植物抗旱性的影响。研究表明,转基因型拟南芥能有效维持体内氧化—还原势,减少MDA的产生,从而缓解干旱胁迫引起的伤害,提高抗旱性。     

siRNA制备技术的研究进展

近年来,siRNA(small interfering RNA)被广泛用于诱导哺乳动物体系中的RNA干扰。目前有五种siRNA制备方法：化学合成法、体外转录法、RNase Ⅲ家族体外消化法、表达载体法和表达框架法。在这些方法中siRNA序列的选择至关重要。随着药物研究和基因组研究的进展,siRNA的制备技术需要在高通量筛选、稳定性、基因导入和调控等方面进一步发展与完善。作者综述了siRNA序列的选择原则和哺乳动物系统中的siRNA产生方法,并简要讨论了其发展前景。