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Marine environments are a rich source of Actinobacteria and have the potential to produce a wide variety of biologically active secondary metabolites. In this study, we used four selective isolation media to culture Actinobacteria from the sediments collected from the Chukchi Shelf in the Arctic Ocean. A total of 73 actinobacterial strains were isolated. Based on repetitive DNA fingerprinting analysis, we selected 30 representatives for partial characterization according to their phylogenetic diversity, antimicrobial activities and secondary-metabolite biosynthesis genes. Results from the 16S rRNA gene sequence analysis indicated that the 30 strains could be sorted into 18 phylotypes belonging to 14 different genera: Agrococcus, Arsenicicoccus, Arthrobacter, Brevibacterium, Citricoccus, Janibacter, Kocuria, Microbacterium, Microlunatus, Nocardioides, Nocardiopsis, Saccharopolyspora, Salinibacterium and Streptomyces. To our knowledge, this paper is the first report on the isolation of Microlunatus genus members from marine habitats. Of the 30 isolates, 11 strains exhibited antibacterial and/or antifungal activity, seven of which have activities against Bacillus subtilis and Candida albicans. All 30 strains have at least two biosynthetic genes, one-third of which possess more than four biosynthetic genes. This study demonstrates the significant diversity of Actinobacteria in the Chukchi Shelf sediment and their potential for producing biologically active compounds and novel material for genetic manipulation or combinatorial biosynthesis.

Cytokinin (CK) inhibits adventitious root (AR) formation in stem cuttings. Little is known, however, about the mechanism underlying the inhibitory effect. In this study, 2 mg l of exogenous 6-benzyl adenine (6-BA) was administered to 3 and 7-day-old apple rootstocks 'M.26' cuttings (3 and 7 days 6-BA) by transferring them from a rooting medium containing indole-3-butanoic acid to the medium containing 6-BA. Anatomical and morphological observations revealed that the exogenous application of 6-BA inhibited primordia formation in the 3 days 6-BA but not the 7 days 6-BA group. The concentration of auxin (IAA), the ratios of IAA/CK and IAA/abscisic acid were lower in 3 days 6-BA than in 7 days 6-BA. Expression analysis of genes known to be associated with AR formation was also analyzed. In the 3 days 6-BA group, high level of CK inhibited the synthesis and transport of auxin, as a result, low endogenous auxin level suppressed the auxin signaling pathway genes, as were other AR development and cell cycle related genes; all of which had an inhibitory impact on AR primordium formation. On the contrary, low CK level in the 7 days 6-BA, reduced the inhibitory impact on auxin levels, leading to an upregulated expression of genes known to promote AR primordia formation. Collectively, our data indicated that 3-7 days is the time period in which AR primordia formation occurs in cuttings of 'M.26' and that the inhibition of AR development by CK is due to the suppression of AR primordia development over 3-7 days period after culturing in rooting medium.

Adventitious roots (AR) play an important role in the vegetative propagation of apple rootstocks. The potential role of hormone, wounding, and sugar signalling pathways in mediating AR formation has not been adequately explored and the whole co-expression network in AR formation has not been well established in apple. In order to identify the molecular mechanisms underlying AR formation in ‘T337’ apple rootstocks, transcriptomic changes that occur during four stages of AR formation (0, 3, 9 and 16 days) were analyzed using high-throughput sequencing. A total of 4294 differentially expressed genes were identified. Approximately 446 genes related to hormones, wounding, sugar signaling, root development, and cell cycle induction pathways were subsequently selected based on their potential to be involved in AR formation. RT-qPCR validation of 47 genes with known functions exhibited a strong positive correlation with the RNA-seq data. Interestingly, most of the candidate genes involved in AR formation that were identified by transcriptomic sequencing showed auxin-responsive expression patterns in an exogenous Indole-3-butyric acid (IBA)-treatment assay: Indicating that endogenous and exogenous auxin plays key roles in regulating AR formation via similar signalling pathways to some extent. In general, AR formation in apple rootstocks is a complex biological process which is mainly influenced by the auxin signaling pathway. In addition, multiple hormones-, wounding- and sugar-signaling pathways interact with the auxin signaling pathway and mediate AR formation in apple rootstocks.

Adventitious root (AR) formation, which is controlled by endogenous and environmental factors, is indispensable for vegetative asexual propagation. However, comprehensive proteomic data on AR formation are still lacking. The aim of this work was to study indole-3-butyric acid (IBA)-induced AR formation in the dwarf apple rootstock ‘T337’. In this study, the effect of IBA on AR formation was analysed. Subsequent to treatment with IBA, both the rooting rate and root length of ‘T337’ increased significantly. An assessment of hormone levels in basal stem cuttings suggested that auxin, abscisic acid, and brassinolide were higher in basal stem cuttings that received the exogenous IBA application; while zeatin riboside, gibberellins, and jasmonic acid were lower than non-treated basal stem cuttings. To explore the underlying molecular mechanism, an isobaric tags for relative and absolute quantification (iTRAQ)-based proteomic technique was employed to identify the expression profiles of proteins at a key period of adventitious root induction (three days after IBA treatment). In total, 3355 differentially expressed proteins (DEPs) were identified. Many DEPs were closely related to carbohydrate metabolism and energy production, protein homeostasis, reactive oxygen and nitric oxide signaling, and cell wall remodeling biological processes; as well as the phytohormone signaling, which was the most critical process in response to IBA treatment. Further, RT-qPCR analysis was used to evaluate the expression level of nine genes that are involved in phytohormone signaling and their transcriptional levels were mostly in accordance with the protein patterns. Finally, a putative work model was proposed. Our study establishes a foundation for further research and sheds light on IBA-mediated AR formation in apple as well as other fruit rootstock cuttings.

Short-chain fructo-oligosaccharides (scFOS) exert beneficial effects on growth performance and immune function of piglets. However, the effects of scFOS on intestinal integrity of piglets remain to be understood. This study was conducted to investigate the protective effects of scFOS on the intestinal barrier function of piglets. A total of 16 castrated male piglets weaned at 28 d were randomly allocated into 1 of 2 dietary treatments (n ¼ 8): a control diet (CON) or a scFOS-supplemented diet (4 g/kg scFOS substituted the same amount of maize in CON). The experiment lasted 28 d. The average daily scFOS intake of treated group was 1.94 g. Results showed that scFOS consumption increased average daily gain and decreased feed to gain ratio and diarrhoea index (p < .05). scFOS-fed piglets had lower serum D-lactate, interleukin 1b (IL-1b), interleukin 6 (IL-6) and tumour necrosis factor-alpha (TNF-a) concentrations than CON-fed piglets (p < .05). scFOS consumption increased intestinal expression of zona occludens 1 (ZO1), occluding (OCLN) and claudin 1 (CLDN1) (p < .05). scFOS supplementation down-regulated IL-1b expression in jejunal mucosa and IL-6 expression in ileal mucosa (p < .05). scFOS-fed piglets had higher acetic acid level in colonic chyme than their counterparts (p < .05). scFOS consumption increased relative abundances of Bacteroidetes, Lactobacillus spp., Prevotella spp. and Bifidobacterium spp. in colonic chyme (p < .05). In conclusion, post-weaning scFOS consumption improved performance and intestinal integrity of piglets by suppressing mucosal inflammation, increasing production of short-chain fatty acids and modulating microbiota composition in the hindgut. HIGHLIGHTSDietary supplementation of 4 g/kg short-chain fructo-oligosaccharides (scFOS) improved growth performance of weaning piglets. Dietary scFOS inclusion enhanced gut integrity and ameliorated intestinal inflammatory response. scFOS consumption resulted in increased short-chain fatty acids production and altered microbiota composition in the hindgut of piglets. ARTICLE HISTORY

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