wearable devices, [4] soft electronics, [5,6] battery binders, [7][8][9] etc. Among these versatile materials, self-healing hydrogels, which can recover their original properties through autonomous healing after suffering from damages, exhibit an enormous potential in the fields of wound closure, [10,11] scaffolds for tissue engineering, [12,13] drug/cell delivery devices, [14][15][16] and so on.In nature, marine mussels can tightly attach to almost all surfaces by secreting mussel adhesive proteins (MAPs). [17] In addition, the adhesion property of MAPs is attributed to the presence of a special catechol-containing amino acid compound, 3,4-dihydroxyphenylalanine (DOPA). [18] The catechol groups of DOPA are easy oxidized to quinones in alkaline condition [1] and subsequently react with nucleophiles such as amines and thiols to form the 3D net structure of hydrogel via Schiff's base and Michael addition reactions. [19] Additionally, the catechol moieties endow DOPA with the capability to complex with various metal ions in order to produce coordination-crosslinked hydrogels. Owing to the versatility of DOPA, it has been coupled through various reactions to numerous macromolecules, including chitosan, [20] gelatin, [19] and polyethylene glycol (PEG). [21] This has allowed to fabricate mussel-inspired materials with self-healing and adhesive properties. The high price and potential neurotransmission effect of DOPA limit its commercial applications, however, and consequently the search of alternatives to DOPA is necessary. [22] Tannic acid (TA), a plant-derived polyphenolic compound, consists of a glucose core and ester-linked peripheral gallol groups (three adjacent hydroxyls attached to benzene). [23] With these functional groups, TA is capable to precipitate proteins (collagen and gelatin) by multi-point hydrogen bond and hydrophobic interactions. [24] The two adjacent phenolic hydroxyls of gallols in TA can also chelate metal ions (e.g., Fe 3+ , Al 3+ , Cr 3+ ) in the form of oxygen anion to form stable pentacyclic complexes. Although the third phenol hydroxyl is not involved in the formation of these pentacyclic structures, it can encourage the dissociation of the other two adjacent OH groups and accelerate the coordination reaction promoting its stability. [25] In addition, TA presents a good antioxidant capacity. The gallols of TA are oxidized to form quinones that further undergo nucleophilic Hydrogels Hydrogels, especially the ones with self-recovery and adhesive performances, have attracted more and more attention owing to their wide practical potential in the biomedical field involving cell delivery, wound filling, and tissue engineering. Tannic acid (TA), a nature-derived gallol-rich polyphenol, exhibits not only unique chelating properties with transition metal cations but also desirable anti-oxidation properties and strong bonding capability to proteins and gelatin. Thus, taking advantage of the versatility of TA, a one-pot method is proposed herein to produce TA-modified gelatin hydrogels with the aid ...

MicroRNA (miRNA) plays an important role in the control of gene expression. HYPONASTIC LEAVES1 (HYL1) is a double-stranded RNA-binding protein that forms a complex with DICER-LIKE1 (DCL1) and SERRATE (SE) to process primary miRNA (pri-miRNA) into mature miRNA. Although HYL1 has been shown to partner with DCL1 to enhance miRNA accuracy, the mechanism by which HYL1 selects the DCL1-targeted cleavage sites in pri-miRNA has remained unknown. By mutagenesis of HYL1 and analysis of in vivo pri-miRNA processing, we investigated the role of HYL1 in pri-miRNA cleavage. HYL1 forms homodimers in which the residues Gly147 and Leu165 in the dsRBD2 domain are shown to be critical. Disruption of HYL1 homodimerization causes incorrect cleavage at sites in pri-miRNA without interrupting the interaction of HYL1 with DCL1 and accumulation of pri-miRNAs in HYL1/pri-miRNA complexes, leading to a reduction in the efficiency and accuracy of miRNAs that results in strong mutant phenotypes of the plants. HYL1 homodimers may function as a molecular anchor for DCL1 to cleave at a distance from the ssRNA–dsRNA junction in pri-miRNA. These results suggest that HYL1 ensures the correct selection of pri-miRNA cleavage sites through homodimerization and thus contributes to gene silencing and plant development.

The internal boundary between inner and outer microsporangia within anthers is essential for male fertility of vascular plants. Dehiscence zones embedded in the boundary release pollen for fertilization. However, the molecular mechanism underlying boundary formation in anthers remains poorly understood. Here, we report that microRNA166 (miR166) and its target PHABULOSA (PHB) regulate SPOROCYTELESS/NOZZLE (SPL/NZZ), which controls microsporogenesis. In developing anthers of Arabidopsis (Arabidopsis thaliana), the expression domains of miR165/6 and SPL/NZZ are overlapped and rearranged synchronously. Dominant mutation of PHB suppresses SPL/NZZ expression on the adaxial sides of stamens, resulting in a thickened boundary, whereas activation of MIR166g up-regulates SPL/NZZ expression, leading to ectopic microsporogenesis in the boundary. PHB limits the expression domains of SPL/NZZ to facilitate construction of the boundary, while miR166 preserves the expression domains of SPL/NZZ by inhibiting PHB to allow the inner microsporangia to take shape. Subsequently, PHB activates the key stem cell maintainer WUSCHEL in anthers to restrict the stomium cells to the boundary so that dehiscence zones develop and release pollen properly. These findings link adaxial/abaxial polarity to microsporogenesis in building of the internal boundary of anthers and thus advance the concepts underlying the establishment of the internal structure of male organs.