Temperature-responsive module of OfAP1 and OfLFY regulates floral transition and floral organ identity in Osmanthus fragrans.

The MADS-box transcription factor APETELA1 (AP1) is crucially important for reproductive developmental processes. The function of AP1 and the classic LFY-AP1 interaction in woody plants are not widely known. Here, the OfAP1-a gene from the continuously flowering plant Osmanthus fragrans 'Sijigui' was characterized, and its roles in regulating flowering time, petal number robustness and floral organ identity were determined using overexpression in Arabidopsis thaliana and Nicotiana tabacum. The expression of OfAP1-a was significantly induced by low ambient temperature and was upregulated with the floral transition process. Ectopic expression OfAP1-a revealed its classic function in flowering and flower ABC models. The expression of OfAP1-a is inhibited by LEAFY (OfLFY) through direct promoter binding, as confirmed by yeast one-hybrid and dual luciferase assays. Arabidopsis plants overexpressing OfAP1-a exhibited accelerated flowering and altered floral organ identities. Moreover, OfAP1-a-overexpressing plants displayed variable petal numbers. Likewise, the overexpression of OfLFY in Arabidopsis and Nicotiana altered petal number robustness and inflorescence architecture, partially by regulating native AP1 in transformed plants. Furthermore, we performed RNA-seq analysis of transgenic Nicotiana plants. DEGs were identified by transcriptome analysis, and we found that the expression of several floral homeotic genes was altered in both OfAP1-a and OfLFY-overexpressing transgenic lines. Our results suggest that OfAP1-a may play important roles during floral transition and development in response to ambient temperature. OfAP1-a functions as a petal number modulator and may directly activate a subset of flowers to regulate floral organ formation. OfAP1-a and OfLFY mutually regulate the expression of each other and coregulate genes that might be involved in these phenotypes related to flowering. The results provide valuable data for understanding the function of the LFY-AP1 module in the reproductive process and shaping floral structures in woody plants.

Accelerated anode and cathode reaction due to direct electron uptake and consumption by manganese dioxide and titanium dioxide composite cathode in degradation of iron composite.

The movement towards the clinical application of iron (Fe) has been hindered by the slow degradation rate in physiological environments. Herein, manganese dioxide (MnO2) particles were compounded with titanium dioxide (TiO2) particles by mechanical ball milling, and then the mixed powders were incorporated into Fe and fabricated into an implant using selective laser melting. On the one hand, MnO2 had a higher work function (5.21 eV) than Fe (4.48 eV), which inclined electrons to transfer from Fe to MnO2 to accelerate the anode reaction. On the other hand, MnO2 catalysed the oxygen reduction reaction (ORR) through a four-step proton-electron-coupled reaction, which caused more oxygen to flow into the sample to improve the cathode performance. Besides, anatase TiO2 with high conductivity was compounded with MnO2 to construct a composite cathode, which facilitated electron transport from the cathode to the electrolyte, further consuming electrons and promoting cathode reaction. Results showed that Fe-MnO2-TiO2 had a high limiting current density of 5.32 mA·cm-2 and a large half-wave potential of -767.4 mV, indicating an enhanced ORR activity. More significantly, Fe-MnO2-TiO2 had a higher average electron transfer number (2.9) than Fe-MnO2 (2.5), demonstrating a faster electronic consumption reaction and higher cathode performance. In addition, the Fe-MnO2-TiO2 also exhibited fast instantaneous and long-term degradation rates (0.33 ± 0.03 and 0.19 ± 0.02 mm/year), suggesting a high anode dissolution rate. In conclusion, introducing the cathode with high work function and ORR activity provides novel pathways for accelerating the degradation rate of Fe-based implants.

Phosphoproteome analysis reveals the involvement of protein dephosphorylation in ethylene-induced corolla senescence in petunia.

BACKGROUND: Senescence represents the last stage of flower development. Phosphorylation is the key posttranslational modification that regulates protein functions, and kinases may be more required than phosphatases during plant growth and development. However, little is known about global phosphorylation changes during flower senescence. RESULTS: In this work, we quantitatively investigated the petunia phosphoproteome following ethylene or air treatment. In total, 2170 phosphosites in 1184 protein groups were identified, among which 2059 sites in 1124 proteins were quantified. To our surprise, treatment with ethylene resulted in 697 downregulated and only 117 upregulated phosphosites using a 1.5-fold threshold (FDR < 0.05), which showed that ethylene negatively regulates global phosphorylation levels and that phosphorylation of many proteins was not necessary during flower senescence. Phosphoproteome analysis showed that ethylene regulates ethylene and ABA signalling transduction pathways via phosphorylation levels. One of the major targets of ethylene-induced dephosphorylation is the plant mRNA splicing machinery, and ethylene treatment increases the number of alternative splicing events of precursor RNAs in petunia corollas. CONCLUSIONS: Protein dephosphorylation could play an important role in ethylene-induced senescence, and ethylene treatment increased the number of AS precursor RNAs in petunia corollas.