The PcMYB44-mediated miR397-PcLACs module regulates defence-induced lignification in pear resistance to fungal disease.

Diseases caused by Alternaria alternata and Botryosphaeria dothidea diminish pear yield and quality, and restrict the pear agricultural industry. Lignification is a conserved mechanism for plant resistance against pathogen invasion. The regulatory mechanisms underlying defence-induced lignification in pear in response to fungal pathogen infection remain unknown. In this study, analysis of lignification level and lignin content in pear revealed that A. alternata and B. dothidea induced lignification, and transcriptomics showed that lignin biosynthesis was affected. To explore whether laccases (LACs) mediated by miR397 regulate lignification in pear, we investigated the role of PcmiR397 in repressing the expression of PcLACs using 5'-RNA ligase-mediated-RACE and co-transformation in tobacco. Opposite expression patterns for PcmiR397 and PcLAC target genes were observed in pear in response to pathogens. Transient transformation in pear demonstrated that silencing PcmiR397 and overexpressing a single PcLAC enhanced resistance to pathogens via lignin synthesis. To further reveal the mechanism underpinning the PcMIR397 response of pear to pathogens, the PcMIR397 promoter was analysed, and pMIR397-1039 was found to be inhibited by pathogen infection. The transcription factor PcMYB44 was up-regulated, and it bound to the PcMIR397 promoter and inhibited transcription following pathogen infection. The results demonstrate the role of PcmiR397-PcLACs in broad-spectrum resistance to fungal disease, and the potential role of PcMYB44 involved in the miR397-PcLAC module in regulating defence-induced lignification. The findings provide valuable candidate gene resources and guidance for molecular breeding to improve resistance to fungal disease in pear.

NO2 gas sensor based on graphene decorated with Ge quantum dots.

We report a NO2 gas sensor based on germanium quantum dots (GeQDs)/graphene hybrids. Graphene was directly grown on germanium through chemical vapor deposition and the GeQDs were synthesized via molecular beam epitaxy. The samples were characterized by atomic force microscope, Raman spectra, scanning electron microscope, x-ray photoelectron spectroscope and transmission electron microscope with energy dispersive x-ray. By introducing GeQDs on graphene, the gas sensor sensitivity to NO2 was improved substantially. With the optimization of the growth time of GeQDs (600 s), the response sensitivity to 10 ppm NO2 can be as high as 3.88, which is 20 times higher than that of the graphene sensor without GeQDs decoration. In addition, the 600 s GeQDs/graphene hybrid sensor exhibits fast response and recovery rates as well as excellent stability. Our work may provide a new route to produce low-power consumption, portable, and room temperature gas sensor which is amenable to mass production.