STAMENLESS1 activates SUPERWOMAN 1 and FLORAL ORGAN NUMBER 1 to control floral organ identities and meristem fate in rice.

Floral patterns are unique to rice and contribute significantly to its reproductive success. SL1 encodes a C2H2 transcription factor that plays a critical role in flower development in rice, but the molecular mechanism regulated by it remains poorly understood. Here, we describe interactions of the SL1 with floral homeotic genes, SPW1, and DL in specifying floral organ identities and floral meristem fate. First, the sl1 spw1 double mutant exhibited a stamen-to-pistil transition similar to that of sl1, spw1, suggesting that SL1 and SPW1 may located in the same pathway regulating stamen development. Expression analysis revealed that SL1 is located upstream of SPW1 to maintain its high level of expression and that SPW1, in turn, activates the B-class genes OsMADS2 and OsMADS4 to suppress DL expression indirectly. Secondly, sl1 dl displayed a severe loss of floral meristem determinacy and produced amorphous tissues in the third/fourth whorl. Expression analysis revealed that the meristem identity gene OSH1 was ectopically expressed in sl1 dl in the fourth whorl, suggesting that SL1 and DL synergistically terminate the floral meristem fate. Another meristem identity gene, FON1, was significantly decreased in expression in sl1 background mutants, suggesting that SL1 may directly activate its expression to regulate floral meristem fate. Finally, molecular evidence supported the direct genomic binding of SL1 to SPW1 and FON1 and the subsequent activation of their expression. In conclusion, we present a model to illustrate the roles of SL1, SPW1, and DL in floral organ specification and regulation of floral meristem fate in rice.

Effect of the Composition of Lanthanide Complexes on Their Luminescence Enhancement by Ag@SiO2 Core-Shell Nanoparticles.

Metal-enhanced luminescence of lanthanide complexes by noble metal nanoparticles has attracted much attention because of its high efficiency in improving the luminescent properties of lanthanide ions. Herein, nine kinds of europium and terbium complexes-RE(TPTZ)(ampca)3·3H2O, RE(TPTZ)(BA)3·3H2O, RE(phen)(ampca)3·3H2O, RE(phen)(PTA)1.5·3H2O (RE = Eu, Tb) and Eu(phen)(BA)3·3H2O (TPTZ = 2,4,6-tri(2-pyridyl)-s-triazine, ampca = 3-aminopyrazine-2-carboxylic acid, BA = benzoic acid, phen = 1,10-phenanthroline, PTA = phthalic acid)-have been synthesized. Meanwhile, seven kinds of core-shell Ag@SiO2 nanoparticles of two different core sizes (80-100 nm and 40-60 nm) and varied shell thicknesses (5, 12, 20, 30 and 40 nm) have been prepared. The combination of these nine types of lanthanide complexes and seven kinds of Ag@SiO2 nanoparticles provides an opportunity for a thorough investigation of the metal-enhanced luminescence effect. Luminescence spectra analysis showed that the luminescence enhancement factor not only depends on the size of the Ag@SiO2 nanoparticles, but also strongly relates to the composition of the lanthanide complexes. Terbium complexes typically possess higher enhancement factors than their corresponding europium complexes with the same ligands, which may result from better spectral overlap between the emission bands of Tb complexes and surface plasmon resonance (SPR) absorption bands of Ag@SiO2. For the complexes with the same lanthanide ion but varied ligands, the complexes with high enhancement factors are typically those with excitation wavelengths located nearby the SPR absorption bands of Ag@SiO2 nanoparticles. These findings suggest a combinatorial chemistry strategy is necessary to obtain an optimal metal-enhanced luminescence effect for lanthanide complexes.

Synthesis, characterization and luminescent properties of europium complexes with 2,4,6-tris-(2-pyridyl)-s-triazine as highly efficient sensitizers.

Using 2,4,6-tris-(2-pyridyl)-s-triazine (TPTZ) as a neutral ligand, and p-hydroxybenzoic acid, terephthalic acid and nitrate as anion ligands, five novel europium complexes have been synthesized. These complexes were characterized using elemental analysis, rare earth coordination titrations, UV/vis absorption spectroscopy and infrared spectroscopy. Luminescence spectra, luminescence lifetime and quantum efficiency were investigated and the mechanism discussed in depth. The results show that the complexes have excellent emission intensities, long emission lifetimes and high quantum efficiencies. The superior luminescent properties of the complexes may be because the triplet energy level of the ligands matches well with the lowest excitation state energy level of Eu(3+). Moreover, changing the ratio of the ligands and metal ions leads to different luminescent properties. Among the complexes, Eu2(TPTZ)2(C8H4O4)(NO3)4(C2H5OH)·H2O shows the strongest luminescence intensity, longest emission lifetime and highest quantum efficiency.

Synthesis, crystal structure and fluorescence properties of terbium complexes with phenoxyacetic acid and 2,4,6-tris-(2-pyridyl)-s-triazine.

Two complexes of Tb(3+), Gd(3+) /Tb(3+) and one heteronuclear crystal Gd(3+)/Tb(3+) with phenoxyacetic acid (HPOA) and 2,4,6-tris-(2-pyridyl)-s-triazine (TPTZ) have been synthesized. Elemental analysis, rare earth coordination titration, inductively coupled plasma atomic emission spectrometry (ICP-AES) and thermogravimetric analysis-differential scanning calorimetry (TG-DSC) analysis show that the two complexes are Tb2 (POA)6 (TPTZ)2 · 6H2O and TbGd(POA)6 (TPTZ)2 · 6H2O, respectively. The crystal structure of TbGd(POA)6 (TPTZ)2 · 2CH3OH was determined using single-crystal X-ray diffraction. The monocrystal belongs to the triclinic system with the P-1 space group. In particular, each metal ion is coordinately bonded to three nitrogen atoms of one TPTZ and seven oxygen atoms of three phenoxyacetic ions. Furthermore, there exist two coordinate forms between C6H5OCH2COO(-) and the metal ions in the crystal. One is a chelating bidentate, the other is chelating and bridge coordinating. Fluorescence determination shows that the two complexes possess strong fluorescence emissions. Furthermore, the fluorescence intensity of the Gd(3+)/Tb(3+) complex is much stronger than that of the undoped complex, which may result from a decrease in the concentration quench of Tb(3+) ions, and intramolecular energy transfer from the ligands coordinated with Gd(3+) ions to Tb(3+) ions.