枯草芽胞杆菌基因组混组方法

基因组混组作为一种育种方法,通过循环原生质体融合等手段,使得不同菌株来源的基因组能够得到充分重组,增加将正向突变整合到同一重组子中的机会。使用4株带有4种不同标记的枯草芽胞杆菌亲本为初始菌株,通过循环转化、循环转导或循环原生质体融合的手段进行基因组混组,统计后代中非亲本类型占整个群体的比例,以衡量基因组混组的效果。分别经过5轮循环原生质体融合、循环转化或者循环转导,结果显示,重组程度较高者在后代群体中的比例较低,带有4种标记的后代未出现,带有3种标记的后代最高分别为4.53×10?4、1.64×10?4、4.47×10?3,明显低于文献报道的天蓝色链霉菌中同样实验的结果:带4种和3种标记的后代分别占2.5%、17%。对比上述实验的结果和文献报道的天蓝色链霉菌、乳杆菌基因组混组的结果,并结合计算机模拟循环融合过程,分析后认为:要达到较充分的基因组混组,需要有能够实现微生物细胞间高频重组的操作技术作为基础,重组频率应该不低于10?3～10?2数量级。     

Movement protein Pns6 of rice dwarf phytoreovirus has both ATPase and RNA binding activities

Cell-to-cell movement is essential for plant viruses to systemically infect host plants. Plant viruses encode movement proteins (MP) to facilitate such movement. Unlike the well-characterized MPs of DNA viruses and single-stranded RNA (ssRNA) viruses, knowledge of the functional mechanisms of MPs encoded by double-stranded RNA (dsRNA) viruses is very limited. In particular, many studied MPs of DNA and ssRNA viruses bind non-specifically ssRNAs, leading to models in which ribonucleoprotein complexes (RNPs) move from cell to cell. Thus, it will be of special interest to determine whether MPs of dsRNA viruses interact with genomic dsRNAs or their derivative sRNAs. To this end, we studied the biochemical functions of MP Pns6 of Rice dwarf phytoreovirus (RDV), a member of Phytoreovirus that contains a 12-segmented dsRNA genome. We report here that Pns6 binds both dsRNAs and ssRNAs. Intriguingly, Pns6 exhibits non-sequence specificity for dsRNA but shows preference for ssRNA sequences derived from the conserved genomic 5'- and 3'-terminal consensus sequences of RDV. Furthermore, Pns6 exhibits magnesium-dependent ATPase activities. Mutagenesis identified the RNA binding and ATPase activity sites of Pns6 at the N- and C-termini, respectively. Our results uncovered the novel property of a viral MP in differentially recognizing dsRNA and ssRNA and establish a biochemical basis to enable further studies on the mechanisms of dsRNA viral MP functions.     

Redox status regulates subcelluar localization of PpTGA1 associated with a BABA-induced priming defence against Rhizopus rot in peach fruit

Molecular Biology Reports - This study attempted to characterize the involvement of a change in the redox status and subcellular localization in the BABA-induced priming resistance of peach fruit...     

Cardioprotection of H2S by downregulating iNOS and upregulating HO-1 expression in mice with CVB3-induced myocarditis

Aims

To explore the effects and potential mechanisms of hydrogen sulfide (H₂S) in CVB3-induced mice with myocarditis.

Main methods

A total of 75 six-week-old inbred male Balb/c mice were divided randomly into four groups (N, C, P and S). Group N was the negative control. The others were inoculated intraperitoneally (i.p.) with CVB3. Subsequently, groups P and S were injected i.p. once a day with DL-Proparglygylcine (PAG) and NaHS respectively. Group C was the positive control. Inducible nitric oxide synthase (iNOS) and heme oxygenase-1(HO-1) expression on cardiac tissues were evaluated by histopathological examination, immunohistochemistry, RT-PCR and Western blot.

Key findings

The heart-weight to body-weight (HW/BW) ratio, the histologic scores and the iNOS mRNA and protein expression levels were higher, and the HO-1 mRNA and protein expression levels were lower in mice treated with PAG than those mice solely inoculated with CVB3. Mice in group S had a significant decreased in the HW/BW ratio, the histologic scores and the iNOS mRNA and protein expression levels, and had a significant increased in the HO-1 mRNA and protein expression levels compared to the mice in group C. H₂S can attenuate inflammatory cell infiltration, alleviate cardiac edema, and limit myocardial lesions.

Significance

Our data support that H₂S can inhibit iNOS overexpression and induce HO-1 expression, both of which contribute to the cardioprotection of H₂S in CVB3-induced mice myocarditis.     

IKK interacts with rictor and regulates mTORC2

mTORC2, the mammalian target of rapamycin complex 2 is activated by upstream growth factors, and performs two major functions, phosphorylation of AKT at the serine of 473 and cell cycle-dependent organization of actin cytoskeleton. However, the mechanisms through which mTORC2 is triggered by these signals remain unclear. We demonstrated, for the first time, that inhibitor of nuclear factor κ-B kinase (IKK) interacted with rictor and regulated mTORC2 activity. Not only endogenously, but ectopically expressed IKK α and IKK β physically interacted with rictor. An in vitro binding assay revealed that rictor interacted with IKKα and IKKβ from amino acids 999 to 1397. Moreover, chemical inhibition of IKK, knockdown of IKK by small interference RNA (siRNA), or ectopic expression of kinase-dead IKK (IKK KD) repressed phosphorylation of AKT (S473) in a variety of cell lines and decreased the kinase activity of mTORC2. In NIH 3 T3 cells, inhibition of IKK also reduced phosphorylation of protein kinase α (PKCα) (S657) and resulted in disorganization of actin cytoskeleton. Interestingly, the interaction between IKKα/β and rictor was increased, while the mTOR-rictor association was attenuated by inhibition of IKK. We identified a novel signaling mechanism for the regulation of mTORC2 by IKK: IKK interacted with rictor and regulated the function of mTORC2 including phosphorylation of AKT (S473) and organization of actin cytoskeleton. Inactivated IKK interacted with rictor and competed against mTOR, which resulted in a reduced mTORC2 level and a decrease in mTORC2 activity.     

Rice Dwarf Virus P2 Protein Hijacks Auxin Signaling by Directly Targeting the Rice OsIAA10 Protein,Enhancing Viral Infection and Disease Development

The phytohormone auxin plays critical roles in regulating myriads of plant growth and developmental processes. Microbe infection can disturb auxin signaling resulting in defects in these processes, but the underlying mechanisms are poorly understood. Auxin signaling begins with perception of auxin by a transient co-receptor complex consisting of an F-box transport inhibitor response 1/auxin signaling F-box (TIR1/AFB) protein and an auxin/indole-3-acetic acid (Aux/IAA) protein. Auxin binding to the co-receptor triggers ubiquitination and 26S proteasome degradation of the Aux/IAA proteins, leading to subsequent events, including expression of auxin-responsive genes. Here we report that Rice dwarf virus (RDV), a devastating pathogen of rice, causes disease symptoms including dwarfing, increased tiller number and short crown roots in infected rice as a result of reduced sensitivity to auxin signaling. The RDV capsid protein P2 binds OsIAA10, blocking the interaction between OsIAA10 and OsTIR1 and inhibiting 26S proteasome-mediated OsIAA10 degradation. Transgenic rice plants overexpressing wild-type or a dominant-negative (degradation-resistant) mutant of OsIAA10 phenocopy RDV symptoms are more susceptible to RDV infection; however, knockdown of OsIAA10 enhances the resistance of rice to RDV infection. Our findings reveal a previously unknown mechanism of viral protein reprogramming of a key step in auxin signaling initiation that enhances viral infection and pathogenesis.