Promoted off-on recognition of H2O2 based on the fluorescence of silicon quantum dots assembled two-dimensional PEG-MnO2 nanosheets hybrid nanoprobe.

An "off-on" assay system for H2O2 determination was developed based on assembling ultra-bright fluorescent silicon quantum dots (SiQDs) and PEG-MnO2 nanosheets. Among them, SiQDs acted as fluorometric reporter, which can effectively eliminate the interference of plant pigments under excitation of 365 nm. PEG-MnO2 nanosheets played dual function of nanoquencher and H2O2 recognizer. Unlike previous reports, the quenching mechanism of SiQDs by PEG-MnO2 nanosheets is attributed to both the associative effect of inner filter effect and the static quenching effect. Thus, the fluorescence intensity of SiQDs at 445 nm decreased with increasing concentration of PEG-MnO2 nanosheets. After addition of H2O2, PEG-MnO2 nanosheets were reduced to Mn2+, consequently resulting in the recovery of the SiQDs fluorescence. Combined with these properties, an off-on fluorescent method was built for determination of H2O2 in plant leaves with high sensitivity and selectivity. The present method has two linear ranges: from 0.05 to 1 µM with a detection limit of 0.09 µM and from 1 to 80 µM with a detection limit of 4.04 µM. Graphical abstract Schematic representation of the mechanism of SiQD/PEG-MnO2 nanoprobe for determination of H2O2.

Biomimetic preparation of silicon quantum dots and their phytophysiology effect on cucumber seedlings.

In this study, a biomimetic synthetic strategy was proposed for a facile preparation of red fluorescent silicon quantum dots (SiQDs) using unicellular algae of diatoms as reaction precursor. The resultant nontoxic SiQDs of ∼2.0 nm diameter display remarkable red luminescence, high quantum yield (∼15%) and narrow full width at half maximum (FWHM, ∼35 nm). Specifically, as-prepared SiQDs show promise as regulators of plant growth. After cultivating cucumber seedlings with SiQDs, the growth of cucumber seedlings has been significant promoted within a wide range of SiQDs concentrations (0.01-0.3 mg mL-1). The total weight of cucumber seedlings significantly increased by 51.91% (P < 0.001) compared with weight of the control group after incubation for 10 days. Moreover, it was discovered that the growth of cucumber seedlings is positively correlated with the water uptake rate of roots. After a 5 day incubation, the optimum concentration of SiQDs significantly increased water uptake rate of roots by 74.6% compared with that of the control group. Real-time fluorescence quantitative polymerase chain reaction (RT-PCR) analysis revealed that the expression of aquaporin gene in cucumber roots treated with SiQDs increased significantly compared to that of the control group. This is the first report regarding a phytophysiology effect of red fluorescent SiQDs on cucumber seedlings growth. The results widen the range of applications of SiQDs in plant science.

Overexpression of CsCaM3 Improves High Temperature Tolerance in Cucumber.

High temperature (HT) stress affects the growth and production of cucumbers, but genetic resources with high heat tolerance are very scarce in this crop. Calmodulin (CaM) has been confirmed to be related to the regulation of HT stress resistance in plants. CsCaM3, a CaM gene, was isolated from cucumber inbred line "02-8." Its expression was characterized in the present study. CsCaM3 transcripts differed among the organs and tissues of cucumber plants and could be induced by HTs or abscisic acid, but not by salicylic acid. CsCaM3 transcripts exhibited subcellular localization to the cytoplasm and nuclei of cells. Overexpression of CsCaM3 in cucumber plants has the potential to improve their heat tolerance and protect against oxidative damage and photosynthesis system damage by regulating the expression of HT-responsive genes in plants, including chlorophyll catabolism-related genes under HT stress. Taken together, our results provide useful insights into stress tolerance in cucumber.

RNA-Seq-derived identification of differential transcription in the eggplant (Solanum melongena) following inoculation with bacterial wilt.

Eggplant (Solanum melongena) is a major vegetable crop worldwide. However, it is susceptible to bacterial wilt (BW) caused by Ralstonia solanacearum, which has become an important factor limiting eggplant yield and quality. The underlying mechanism of BW remains unknown. Here, RNA-sequencing was used to characterize the transcriptomes of resistant (R) and susceptible (S) strains before (R0, S0) and after (R1, S1) R. solanacearum inoculation. After the removal of low-quality sequences and assembly, 125,852 contigs, 122,508 transcripts, and 68,792 unigenes were identified, with 51,165 non-redundant unigenes annotated. Functional annotations were provided for 11,039 unigenes using four databases (NCBI Nr, Swissprot, KEGG and COG database). A total of 1137 and 9048 genes were found to be up- and down-regulated, respectively, in R0 relative to R1 samples, with 738 and 217 up- and down-regulated in S0 relative to R0 samples, 6087 and 5832 up- and down-regulated in S0 relative to S1 samples, and 4712 and 12,523 up- and down-regulated in S1 relative to R1 samples, respectively. In conclusion, our results provide useful insights into the potential mechanism of BW and are an important basis for further analysis.