The in vitro differentiation of insulin-producing β-like cells can model aspects of human pancreatic development. Here we generate 95,308 single cell transcriptomes and reconstruct a lineage tree of the entire differentiation process from hESCs to β-like cells to study temporally regulated genes during differentiation. We identify so-called ‘switch genes’ at the branch point of endocrine/non-endocrine cell fate choice, revealing insights into the mechanisms of differentiation promoting reagents, such as NOTCH and ROCKII inhibitors, and providing improved differentiation protocols. Over 20% of all detectable genes are activated multiple times during differentiation, even though their enhancer activation is usually unimodal, indicating extensive gene reuse driven by different enhancers. We also identify a stage-specific enhancer in the TCF7L2 diabetes GWAS locus that drives a transient wave of gene expression in pancreatic progenitors. Finally, we develop a web app to visualize gene expression on the lineage tree, providing a comprehensive single cell data resource for researchers studying islet biology and diabetes.
Background Molasses is a wildly used feedstock for fermentation, but it also poses a severe wastewater-disposal problem worldwide. Recently, the wastewater from yeast molasses fermentation is being processed into fulvic acid (FA) powder as a fertilizer for crops, but it consequently induces a problem of soil acidification after being directly applied into soil. In this study, the low-cost FA powder was bioconverted into a value-added product of γ-PGA by a glutamate-independent producer of Bacillus velezensis GJ11. Results FA power could partially substitute the high-cost substrates such as sodium glutamate and citrate sodium for producing γ-PGA. With FA powder in the fermentation medium, the amount of sodium glutamate and citrate sodium used for producing γ-PGA were both decreased around one-third. Moreover, FA powder could completely substitute Mg2+, Mn2+, Ca2+, and Fe3+ in the fermentation medium for producing γ-PGA. In the optimized medium with FA powder, the γ-PGA was produced at 42.55 g/L with a productivity of 1.15 g/(L·h), while only 2.87 g/L was produced in the medium without FA powder. Hydrolyzed γ-PGA could trigger induced systemic resistance (ISR), e.g., H2O2 accumulation and callose deposition, against the pathogen’s infection in plants. Further investigations found that the ISR triggered by γ-PGA hydrolysates was dependent on the ethylene (ET) signaling and nonexpressor of pathogenesis-related proteins 1 (NPR1). Conclusions To our knowledge, this is the first report to use the industry waste, FA powder, as a sustainable substrate for microbial synthesis of γ-PGA. This bioprocess can not only develop a new way to use FA powder as a cheap feedstock for producing γ-PGA, but also help to reduce pollution from the wastewater of yeast molasses fermentation.
Plant growth‐promoting rhizobacteria (PGPRs) confer benefits to crops by producing volatile organic compounds (VOCs) to trigger induced systemic tolerance (IST). Here we show that Bacillus velezensis GJ11, a kind of PGPRs, produce VOCs such as 2,3‐butanediol and acetoin to trigger IST and cause stomatal closure against O3 injury in tobacco plants. Compared to 2,3‐butanediol, acetoin was more effective on triggering IST against O3 injury. The bdh‐knockout strain GJ11Δbdh with a blocked metabolic pathway from acetoin to 2,3‐butanediol produced more acetoin triggering stronger IST against O3 injury than GJ11. Both acetoin and GJ11Δbdh effectively enhance the antioxidant enzymes activity (e.g. superoxide dismutase and catalases) that is favorable for scavenging the reactive oxygen species like H2O2 in leaves after exposure to O3. Consequently, less H2O2 accumulation was observed, and reasonably less chlorophylls and proteins were damaged by H2O2 in the tobacco leaves treated with acetoin or GJ11Δbdh. The field experiment also showed that both acetoin and GJ11Δbdh could protect tobacco plants from O3 injury after application by root‐drench. This study provides new insights into the role of rhizobacterial B. velezensis and its volatile component of acetoin in triggering defense responses against stresses such as O3 in plants.
Background: Molasses is a wildly used feedstock for fermentation, but it also poses a severe wastewater-disposal problem worldwide. Recently, the wastewater from yeast molasses fermentation is being processed into fulvic acid (FA) powder as a fertilizer for crops, but it consequently induces a problem of soil acidification after being directly applied into soil. In this study, the low-cost FA powder was bioconverted into a value-added product of γ-PGA by a glutamate independent producer of Bacillus velezensis GJ11.Results: FA power could partially substitute the high-cost substrates such as sodium glutamate and citrate sodium for producing γ-PGA. With FA powder in the fermentation medium, the amount of sodium glutamate and citrate sodium used for producing γ-PGA were both decreased around one third. Moreover, FA powder could completely substitute Mg2+, Mn2+, Ca2+ and Fe3+ in the fermentation medium for producing γ-PGA. In the optimized medium with FA powder, the γ-PGA was produced at 42.55 g/L with a productivity of 1.15 g/(L·h), while only 2.87 g/L was produced in the medium without FA powder. Hydrolyzed γ-PGA could trigger induced systemic resistance (ISR), e.g. H2O2 accumulation and callose deposition, against the pathogen’s infection in plants. Further investigations found the ISR triggered by γ-PGA hydrolysates was dependent on the ethylene (ET) signalling and nonexpressor of pathogenesis-related proteins 1 (NPR1). Conclusions: To our knowledge, this is the first report to use the industry waste, FA powder, as a sustainable substrate for microbial synthesis of γ-PGA. This bioprocess can not only develop a new way to use FA powder as a cheap feedstock for producing γ-PGA, but also help to reduce pollution from the wastewater of yeast molasses fermentation.
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