We herein present a three-in-one nanoplatform for sensing, self-assembly, and cascade catalysis, enabled by cyclodextrin modified gold nanoparticles (CD@AuNPs). Monodisperse AuNPs 15-20 nm in diameter are fabricated in an eco-friendly way by the proposed one-step colloidal synthesis method using CD as both reducing agents and stabilizers. First, the as-prepared AuNPs are employed as not only scaffolds but energy acceptors for turn-on fluorescent sensing based on guest replacement reaction. Then, the macrocyclic supramolecule functionalized AuNPs can be controllably assembled and form well-defined one- and two-dimensional architectures using tetrakis(4-carboxyphenyl)porphyrin as mediator. Finally, in addition to conventional host-guest interaction based properties, the CD@AuNPs possess unpredictable catalytic activity and exhibit mimicking properties of both glucose oxidase and horseradish peroxidase simultaneously. Especially, the cascade reaction (glucose is first catalytically oxidized and generates gluconic acid and HO; then the enzymatic HO and preadded TMB (3,3',5,5'-tetramethylbenzidine) are further catalyzed into HO and oxTMB, respectively) is well-achieved using the AuNPs as the sole catalyst. By employing a joint experimental-theoretical study, we reveal that the unique catalytic properties of the CD@AuNPs probably derive from the special topological structures of CD molecules and the resulting electron transfer effect from the AuNP surface to the appended CD molecules.

The interaction between plants and plant-growth-promoting rhizobacteria (PGPR) is a complex, reciprocal process. On the one hand, plant compounds such as carbohydrates and amino acids serve as energy sources for PGPR. On the other hand, PGPR promote plant growth by synthesizing plant hormones and increasing mineral availability in the soil. Here, we evaluated the growth-promoting activity of Bacillus subtilis OKB105 and identified genes associated with this activity. The genes yecA (encoding a putative amino acid/polyamine permease) and speB (encoding agmatinase) are involved in the secretion or synthesis of polyamine in B. subtilis OKB105. Disruption of either gene abolished the growth-promoting activity of the bacterium, which was restored when polyamine synthesis was complemented. Moreover, high-performance liquid chromatography analysis of culture filtrates of OKB105 and its derivatives demonstrated that spermidine, a common polyamine, is the pivotal plant-growth-promoting compound. In addition, real-time polymerase chain reaction analysis revealed that treatment with B. subtilis OKB105 induced expansin gene (Nt-EXPA1 and Nt-EXPA2) expression and inhibited the expression of the ethylene biosynthesis gene ACO1. Furthermore, enzyme-linked immunosorbent assay analysis showed that the ethylene content in plant root cells decreased in response to spermidine produced by OKB105. Therefore, during plant interactions, OKB105 may produce and secrete spermidine, which induces expansin production and lowers ethylene levels.

Dimethylations of histone H3 lysine 9 and lysine 27 are important epigenetic marks associated with transcription repression. Here, we identified KIAA1718 (KDM7A) as a novel histone demethylase specific for these two repressing marks. Using mouse embryonic stem cells, we demonstrated that KIAA1718 expression increased at the early phase of neural differentiation. Knockdown of the gene blocked neural differentiation and the effect was rescued by the wild-type human gene, and not by a catalytically inactive mutant. In addition, overexpression of KIAA1718 accelerated neural differentiation. We provide the evidence that the pro-neural differentiation effect of KDM7A is mediated through direct transcriptional activation of FGF4, a signal molecule implicated in neural differentiation. Thus, our study identified a dual-specificity histone demethylase that regulates neural differentiation through FGF4.