MicroRNA528 Affects Lodging Resistance of Maize by Regulating Lignin Biosynthesis under Nitrogen-Luxury Conditions.

Lodging under nitrogen (N)-luxury conditions substantially reduces crop yield and seed quality. However, the molecular mechanisms of plant lodging resistance remain largely unclear, especially in maize. We report here that the expression of ZmmiR528, a monocot-specific microRNA, is induced by N luxury but reduced by N deficiency. We show by the thioacidolysis and acetyl bromide analysis that N luxury significantly reduces the generation of H, G, and S monomers of the lignin as well as its total content in maize shoots. We further demonstrate that ZmLACCASE3 (ZmLAC3) and ZmLACCASE5 (ZmLAC5), which encode the copper-containing laccases, are the targets of ZmmiR528. In situ hybridization showed that ZmmiR528 is mainly expressed in maize vascular tissues. Knockdown of ZmmiR528 or overexpression of ZmLAC3 significantly increased the lignin content and rind penetrometer resistance of maize stems. In contrast, transgenic maize plants overexpressing ZmmiR528 had reduced lignin content and rind penetrometer resistance and were prone to lodging under N-luxury conditions. RNA-sequencing analysis revealed that ZmPAL7 and ZmPAL8 are upregulated in transgenic maize lines downregulating ZmmiR528. Under N-luxury conditions, the expression levels of ZmPALs were much higher in ZmmiR528-knockdown lines than in the wild type and transgenic maize lines overexpressing ZmmiR528. Taken together, these results indicate that, by regulating the expression of ZmLAC3 and ZmLAC5, ZmmiR528 affects maize lodging resistance under N-luxury conditions.

Mechanically strong and pH-responsive carboxymethyl chitosan/graphene oxide/polyacrylamide nanocomposite hydrogels with fast recoverability.

The biocompatible, quickly recoverable, mechanically strong and tough polymer hydrogels have great potential for biomedical applications. A novel carboxymethyl chitosan (CMCTs)/graphene oxide (GO)/polyacrylamide (PAM) nanocomposite (NC) hydrogel with excellent mechanical performance was synthesized through a facile, one-pot free radical polymerization, using GO nanosheets as the crosslink centers instead of toxic organic molecules. The content of GO nanosheets and CMCTs has great influence on the mechanical properties of CMCTs/GO/PAM NC hydrogels. When the amount of GO nanosheets is 0.118 wt % and CMCTs is 1.5 wt % (to the total weight of CMCTs and acrylamide), CMCTs/GO/PAM hydrogel displays a compressive stress as high as 5.8 MPa at the breaking deformation of 87.5% and a tensile strength of 223.6 kPa at the failure strain of 631%. Besides, with nearly complete recovery in 1 min at the room temperature after unloading, the CMCTs/GO/PAM hydrogels exhibit excellent fast recoverability. Additionally, the CMCTs/GO/PAM hydrogels also have an obvious pH-responsive property.