ZmbZIP27 regulates nitrogen-mediated leaf angle by modulating lignin deposition in maize

In grain crops such as maize(Zea mays),leaf angle(LA)is a key agronomic trait affecting light interception and thus planting density and yield.Nitrogen(N)affects LA in plants,but we lack a good understanding of how N regulates LA.Here,we report that N deficiency enhanced lignin deposition in the ligular region of maize seedlings.In situ hybridization showed that the bZIP transcription factor gene ZmbZIP27 is mainly expressed in the phloem of maize vascular bundles.Under N-sufficient conditions,transgenic maize overexpressing ZmbZIP27 showed significantly smaller LA compared with wild type(WT).By contrast,zmbzip27_(ems)mutant showed larger LA under both N-deficient and N-sufficient conditions compared with WT.Overexpression of ZmbZIP27 enhanced lignin deposition in the ligular region of maize in the field.We further demonstrated that ZmbZIP27 could directly bind the promoters of the microRNA genes ZmMIR528a and ZmMIR528b and negatively regulate the expression levels of ZmmiR528.ZmmiR528 knockdown transgenic maize displayed erect architecture in the field by increasing lignin content in the ligular region of maize.Taken together,these results indicate that ZmbZIP27 regulates N-mediated LA size by regulating the expression of ZmmiR528 and modulating lignin deposition in maize.

Identification of traits and genes associated with lodging resistance in maize

Lodging is a major problem limiting maize yield worldwide. However, the mechanisms of lodging resistance remain incompletely understood for maize. Here, we evaluated 443 maize accessions for lodging resistance in the field. Five lodging-resistant accessions and five lodging-sensitive accessions were selected for further research. The leaf number, plant height, stem diameter, and rind penetrometer resistance were similar between lodging-resistant and-sensitive inbred lines. The average thickness of sclerenchymatous hypodermis layer was thicker and the vascular area was larger in the lodging-resistant lines compared with lodging-sensitive lines. Although total lignin content in stem tissue did not significantly differ between lodging-resistant and-sensitive lines, phloroglucinol staining revealed that the lignin content of the cell wall in the stem cortex and in the stem vascular tissue near the cortex was higher in the lodging-resistant lines than in the lodging-sensitive lines. Analysis of strand-specific RNA-seq transcriptome showed that a total of 793 genes were up-regulated and 713 genes were down-regulated in lodging-resistant lines relative to lodging-sensitive lines. The up-regulated genes in lodging-resistant lines were enriched in cell wall biogenesis. These results indicated that modification of cell wall biosynthesis would contribute to lodging resistance of maize.

High efficiency and high transmission asymmetric polarization converter with chiral metasurface in visible and near-infrared region

Polarization manipulation of light is of great importance because it could promote development of wireless communications,biosensing,and polarization imaging.In order to use natural light more efficiently,it is highly demanded to design and fabricate high performance asymmetric polarization converters which could covert the natural light to one particular linearly polarized light with high efficiency.Traditionally,polarizers could be achieved by controllers with crystals and polymers exhibiting birefringence.However,the polarizers are bulky in size and the theoretical conversion efficiency of the polarizers is limited to 0.5 with unpolarized light incidence.In this paper,we propose a polarization converter which could preserve high transmission for one linearly polarized light and convert the orthogonal linearly polarized light to its cross-polarized with high transmittance based on a multi-layer chiral metasurface.Theoretical results show that normally incident y-polarized light preserves high transmittance for the wavelength range from 685 nm to 800 nm while the orthogonal normally incident x-polarized light is efficiently converted to the y-polarized light with high transmittance from 725 nm to 748 nm.Accordingly,for unpolarized light incidence,transmittance larger than 0.5 has been successfully achieved in a broadband wavelength range from 712 nm to 773 nm with a maximum transmittance of 0.58 at 732 nm.

Nitrogen supply affects ion homeostasis by modifying root Casparian strip formation through the miR528-LAC3 module in maize

Although nitrogen(N)is known to affect mineral element homeostasis in plants,the molecular mechanisms of interactions between N and other nutrients remain largely unclear.Wereport here that N supply affects ion homeostasis inmaize.Berberine hemisulfate staining and a propidiumiodide penetration assay showed that N luxury significantly delayed Casparian strip(CS)formation in maize roots.We further demonstrated that N-mediated CS formation in maize was independent of RBOHF-activated H2O2 production.N luxury induced the expression of ZmmiR528 inwhole roots and root tips.Knockdown and loss-of-function ofZmmiR528 promoted CS formation under both N-luxury and N-deficient conditions.Both ZmMIR528a and ZmMIR528b contribute to early CS formation under different N conditions.RNA-seq and real-time RT-PCR analysis demonstrated that ZmLAC3,but not ZmLAC5,responded to N treatments.Consistent with results obtained with ZmmiR528 TM transgenic maize and mir528a/b loss-of-function mutants,transgenic maize overexpressing ZmLAC3 displayed early CS formation under different N conditions.Under field conditions,K,Ca,Mn,Cu,Mg,and Zn concentrations were greater in the ear leaf of ZmLAC3-overexpressing transgenicmaize than in the wild type.These results indicate that ZmmiR528 affects CS formation in maize by regulating the expression of ZmLAC3,and modification of CS formation has the potential to improve maize quality.

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

Lodging under nitrogen （N）-Iuxury 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 signifi- cantly 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-lux- ury 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 un- der N-luxury conditions.

The long non-coding RNA PILNCR2 increases low phosphate tolerance in maize by interfering with miRNA399-guided cleavage of ZmPHT1s

Theopen reading regions of ZmPHT1s(inorganic phosphate[Pij transporters)inmaize possess target sites of microRNA399(miR399).However,the relationship between miR399 and ZmPHT1s and its functional importance in response to Pi deficiency remain to be explored.We show here that ZmPHT1;1,ZmPHT1;3,and ZmPHT1;13 are the targets of ZmmiRNA399.We found that a long non-coding RNA,PILNCR2(Pi-deficiency-induced IncRNA 2),is transcribed from the opposing DNA strand of ZmPHT1;1 and predominantly localized in the cytoplasm.A ribonuclease protection assay and an RNA-RNA binding assay showed that PILNCR2 and ZmPHT1s could form the RNA/RNA duplexes in vivo and in vitro.A co-expression assay in N.benthamiana revealed that the PILNCR2/ZmPHT1 RNA/RNA duplexes interfere with miR399-guided cleavage of ZmPHT1 mRNAs.Overexpression of PILNCR2 increased low-Pi tolerance in maize,whereas its knockout and knockdown decreased low-Pi tolerance in maize.Consistently,ZmPHT1;3 and ZmPHT1;13 mRNA abundance was increased in transgenic plants overexpressing PILNCR2 but reduced in its knock-out mutants,suggesting that PILNCR2 positively regulates the mRNA abundance of ZmPHT1;3 and ZmPHT1;13 in maize.Collectively,these results indicate that PILNCR2 plays an important role in maize Pihomeostasisby interfering with miRNA399-guided cleavageof ZmPHT1mRNAs.