Pre-miRNA Hsa-Let-7a-2: a Novel Intracellular Partner of Angiotensin II Type 2 Receptor Negatively Regulating its Signals

G protein-coupled receptors (GPCRs) are the largest family of druggable targets, and their biological functions depend on different ligands and intracellular interactomes. Some microRNAs (miRNAs) bind as ligands to RNA-sensitive toll-like receptor 7 to regulate the inflammatory response, thereby contributing to the pathogenesis of cancer or neurodegeneration. It is unknown whether miRNAs bind to angiotensin II (Ang II) type 2 receptor (AGTR2), a critical protective GPCR in cardiovascular diseases, as ligands or intracellular interactomes. Here, screening for miRNAs that bind to AGTR2, we identified and confirmed that the pre-miRNA hsa-let-7a-2 non-competitively binds to the intracellular third loop of AGTR2. Functionally, intracellular hsa-let-7a-2 overexpression suppressed the Ang II-induced AGTR2 effects such as cAMP lowering, RhoA inhibition, and activation of Src homology 2 domain-containing protein-tyrosine phosphatase 1, whereas hsa-let-7a-2 knockdown enhanced these effects. Consistently, overexpressed hsa-let-7a-2 restrained the AGTR2-induced antiproliferation, antimigration, and proapoptosis of cells, and vasodilation of mesenteric arteries. Our findings demonstrated that hsa-let-7a-2 is a novel intracellular partner of AGTR2 that negatively regulates AGTR2-activated signals.     

外源Spd对低温胁迫下甜瓜幼苗光合与抗氧化特性及其相关基因表达的影响

为探讨外源亚精胺(Spd)诱导甜瓜耐低温胁迫的生理与分子机制,该研究以甜瓜耐低温品种‘世纪蜜’和低温敏感品种‘GL-1’为试验材料,在人工气候箱内采用基质栽培法,对其叶面喷施外源Spd,对低温胁迫及恢复后甜瓜幼苗生长、光合作用、抗氧化酶活性等生理指标进行测定,并利用定量PCR技术分析4种抗氧化酶基因在低温胁迫条件下的表达特性,分析外源Spd缓解低温胁迫的效应。结果表明:(1)低温胁迫显著抑制甜瓜幼苗的生长及其光合作用,降低幼苗叶绿素含量,显著增强抗氧化酶活性及相关基因表达水平,且对品种‘GL-1’影响大于‘世纪蜜’。(2)外源Spd处理可以有效促进甜瓜幼苗的生长,提高叶片叶绿素含量、净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、气孔限制值(Ls)、水分利用效率(WUE),以及最大光化学效率(Fv/Fm)、光系统Ⅱ光能捕获效率(Fv′/Fm′)和表观光合电子传递速率(ETR),降低胞间CO2浓度(Ci)和初始荧光(Fo)。(3)外源Spd可诱导低温胁迫下甜瓜抗氧化酶活性和基因表达量发生改变,并提高了低温胁迫下甜瓜幼苗叶片超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)和抗坏血酸过氧化酶(APX)基因的表达,从而增强这些抗氧化酶活性,有效缓解低温胁迫造成的氧化胁迫伤害。(4)与对照相比,外源Spd对低温胁迫下品种‘GL-1’各指标降低或升高的幅度大于品种‘世纪蜜’。研究发现,Spd有利于甜瓜幼苗在低温胁迫下光合作用的维持,提高光合电子传递效率、光能的捕获与转换,并提高抗氧化酶活性和相关基因表达水平,促进甜瓜幼苗的生长,有效缓解低温胁迫对甜瓜幼苗生长的抑制作用,且Spd对低温敏感品种‘GL-1’缓解效果优于耐低温品种‘世纪蜜’。     

一株高效聚磷解淀粉芽孢杆菌的分离鉴定及其除磷条件优化

[背景]磷是引起水体富营养化的主要营养物质.生物除磷具有成本低、效率高且适用范围广等特点,成为近年来水处理研究领域的热点.目前虽然有一些聚磷菌被筛选获得,但它们的除磷效率不高,其除磷条件尚需优化.聚磷菌的固定化及回收利用也亟待研究.[目的]分离筛选并鉴定高效聚磷菌株,优化除磷环境条件,研究吸附材料对所筛菌株除磷的影响,...     

Isotopic evidence for increased carbon and nitrogen exchanges between peatland plants and their symbiotic microbes with rising atmospheric CO2 concentrations since 15,000 cal. year BP

Whether nitrogen (N) availability will limit plant growth and removal of atmospheric CO₂ by the terrestrial biosphere this century is controversial. Studies have suggested that N could progressively limit plant growth, as trees and soils accumulate N in slowly cycling biomass pools in response to increases in carbon sequestration. However, a question remains over whether longer-term (decadal to century) feedbacks between climate, CO₂ and plant N uptake could emerge to reduce ecosystem-level N limitations. The symbioses between plants and microbes can help plants to acquire N from the soil or from the atmosphere via biological N₂ fixation—the pathway through which N can be rapidly brought into ecosystems and thereby partially or completely alleviate N limitation on plant productivity. Here we present measurements of plant N isotope composition (δ¹⁵N) in a peat core that dates to 15,000 cal. year BP to ascertain ecosystem-level N cycling responses to rising atmospheric CO₂ concentrations. We find that pre-industrial increases in global atmospheric CO₂ concentrations corresponded with a decrease in the δ¹⁵N of both Sphagnum moss and Ericaceae when constrained for climatic factors. A modern experiment demonstrates that the δ¹⁵N of Sphagnum decreases with increasing N₂-fixation rates. These findings suggest that plant-microbe symbioses that facilitate N acquisition are, over the long term, enhanced under rising atmospheric CO₂ concentrations, highlighting an ecosystem-level feedback mechanism whereby N constraints on terrestrial carbon storage can be overcome.