Complete genome sequence of Paenibacillus polymyxa SC2, a strain of plant growth-promoting Rhizobacterium with broad-spectrum antimicrobial activity

Paenibacillus polymyxa SC2 is an important plant growth-promoting rhizobacterium (PGPR). Here, we report the complete genome sequence of P. polymyxa SC2. Multiple sets of functional genes have been found in the genome. As far as we know, this is the first complete genome sequence of Paenibacillus polymyxa.     

Molecular features of secondary vascular tissue regeneration after bark girdling in Populus

Regeneration is a common strategy for plants to repair damage to their tissue after attacks from other organisms or physical assaults. However, how differentiating cells acquire regenerative competence and rebuild the pattern of new tissues remains largely unknown. Using anatomical observation and microarray analysis, we investigated the morphological process and molecular features of secondary vascular tissue regeneration after bark girdling in trees. After bark girdling, new phloem and cambium regenerate from differentiating xylem cells and rebuild secondary vascular tissue pattern within 1 month. Differentiating xylem cells acquire regenerative competence through epigenetic regulation and cell cycle re-entry. The xylem developmental program was blocked, whereas the phloem or cambium program was activated, resulting in the secondary vascular tissue pattern re-establishment. Phytohormones play important roles in vascular tissue regeneration. We propose a model describing the molecular features of secondary vascular tissue regeneration after bark girdling in trees. It provides information for understanding mechanisms of tissue regeneration and pattern formation of the secondary vascular tissues in plants.     

Self-sterility in the mutant ‘Zigui shatian’ pummelo (<Emphasis Type="Italic">Citrus grandis</Emphasis> Osbeck) is due to abnormal post-zygotic embryo development and not self-incompatibility

‘Shatian’ pummelo (Citrus grandis Osbeck), one of the main citrus cultivars in China, is self-incompatible, and its pollen tubes are believed to be arrested in style after self-pollination.We have characterized one ‘Shatian’ pummelo mutant, named ‘Zigui shatian’ pummelo. The mutant pummelo had identical DNA ploidy level, morphology (leaf shape, stoma size and density, pollen shape and size) and developmental progress of pistil and male organs to that of the common ‘Shatian’ pummelo. However, unlike the common ‘Shatian’ pummelo, ‘Zigui shatian’ is self-compatible since its pollen tubes can self-pollinate allowing for successful fertilization. Histological analyses of ‘Shatian’ pummelo further verified abnormal post-zygotic development which led to seed abortion. Simple sequence repeats (SSR) analysis revealed polymorphism in 1 of the 120 primers screened showing that ‘Zigui shatian’ and ‘Shatian’ pummelo are different at the DNA level. Taken together, these data suggested mutant ‘Zigui shatian’ pummelo might be derived from ‘Shatian’ pummelo with self-sterility by self-incongruity after self-fertilization.     

Histidine-rich protein Hpn from Helicobacter pylori forms amyloid-like fibrils in vitro and inhibits the proliferation of gastric epithelial AGS cells

Helicobacter pylori causes various gastric diseases, such as gastritis, peptic ulcerations, gastric cancer and mucosa-associated lymphoid tissue lymphoma. Hpn is a histidine-rich protein abundant in this bacterium and forms oligomers in physiologically relevant conditions. In this present study, Hpn oligomers were found to develop amyloid-like fibrils as confirmed by negative stain transition electron microscopy, thioflavin T and Congo red binding assays. The amyloid-like fibrils of Hpn inhibit the proliferation of gastric epithelial AGS cells through cell cycle arrest in the G2/M phase, which may be closely related to the disruption of mitochondrial bioenergetics as reflected by the significant depletion of intracellular ATP levels and the mitochondrial membrane potential. The collective data presented here shed some light on the pathologic mechanisms of H. pylori infections.     

Neurochemical features of enkephalinergic neurons in the mouse trigeminal subnucleus caudalis

Enkephalinergic (ENKergic) neurons have been proposed to play crucial roles in pain modulation in the trigeminal subnucleus caudalis (Vc). To assist an advance in the research of ENKergic neurons, here we used preproenkephalin-green fluorescent protein (PPE-GFP) transgenic mice, in which all ENKergic neurons were fluorescent. We first performed fluorescent in situ hybridization combined with immunofluorescent histochemistry to confirm the specificity of this transgenic mouse and its advantages in showing ENKergic neurons in the Vc. Then based on this useful transgenic mouse, we examined the phenotypic diversity of PPE-GFP neurons by immunostaining for several markers that characterize ENKergic neuron subtypes. About 25.9±1.9% of GFP-positive neurons were regarded as immunoreactive for glutamic acid decarboxylase (GAD)(67) mRNA and 14.7±1.4% of GFP-positive neurons were positive for γ-aminobutyric acid. The proportions of calbindin-, calretinin-positive cells among the ENKergic neurons were 8.4±1.2% and 7.3±1.7%, respectively. Only 1.1±0.1% of GFP-positive neurons colocalized with parvalbumin and no GFP-positive neurons were found to co-express neuronal nitric oxide synthase. We then injected retrograde tracer into the thalamic regions and observed that a small number of ENKergic neurons in the Vc were retrogradely labeled with the tracer. The present results provide a detailed morphological evidence of the neurochemical features of ENKergic neurons. These results have broad implications for understanding the functional roles of ENKergic neurotransmission in the Vc.