Genome-Wide Identification of the MPK Gene Family and Expression Analysis under Low-Temperature Stress in the Banana.

Mitogen-activated protein kinases (MAPKs and MPKs) are important in the process of resisting plant stress. In this study, 21, 12, 18, 16, and 10 MPKs were identified from Musa acuminata, Musa balbisiana, Musa itinerans, Musa schizocarpa, and Musa textilis, respectively. These MPKs were divided into Group A, B, C, and D. Phylogenetic analysis revealed that this difference in number was due to the gene shrinkage of the Group B subfamily of Musa balbisiana and Musa textilis. KEGG annotations revealed that K14512, which is involved in plant hormone signal transduction and the plant-pathogen interaction, was the most conserved pathway of the MPKs. The results of promoter cis-acting element prediction and focTR4 (Fusarium oxysporum f. sp. cubense tropical race 4) transcriptome expression analysis preliminarily confirmed that MPKs were relevant to plant hormone and biotic stress, respectively. The expression of MPKs in Group A was significantly upregulated at 4 °C, and dramatically, the MPKs in the root were affected by low temperature. miR172, miR319, miR395, miR398, and miR399 may be the miRNAs that regulate MPKs during low-temperature stress, with miR172 being the most critical. miRNA prediction and qRT-PCR results indicated that miR172 may negatively regulate MPKs. Therefore, we deduced that MPKs might coordinate with miR172 to participate in the process of the resistance to low-temperature stress in the roots of the banana. This study will provide a theoretical basis for further analysis of the mechanism of MPKs under low-temperature stress of bananas, and this study could be applied to molecular breeding of bananas in the future.

Genome-Wide Identification and Expression Analysis Reveals the B3 Superfamily Involved in Embryogenesis and Hormone Responses in Dimocarpus longan Lour.

B3 family transcription factors play an essential regulatory role in plant growth and development processes. This study performed a comprehensive analysis of the B3 family transcription factor in longan (Dimocarpus longan Lour.), and a total of 75 DlB3 genes were identified. DlB3 genes were unevenly distributed on the 15 chromosomes of longan. Based on the protein domain similarities and functional diversities, the DlB3 family was further clustered into four subgroups (ARF, RAV, LAV, and REM). Bioinformatics and comparative analyses of B3 superfamily expression were conducted in different light and with different temperatures and tissues, and early somatic embryogenesis (SE) revealed its specific expression profile and potential biological functions during longan early SE. The qRT-PCR results indicated that DlB3 family members played a crucial role in longan SE and zygotic embryo development. Exogenous treatments of 2,4-D (2,4-dichlorophenoxyacetic acid), NPA (N-1-naphthylphthalamic acid), and PP333 (paclobutrazol) could significantly inhibit the expression of the DlB3 family. Supplementary ABA (abscisic acid), IAA (indole-3-acetic acid), and GA3 (gibberellin) suppressed the expressions of DlLEC2, DlARF16, DlTEM1, DlVAL2, and DlREM40, but DlFUS3, DlARF5, and DlREM9 showed an opposite trend. Furthermore, subcellular localization indicated that DlLEC2 and DlFUS3 were located in the nucleus, suggesting that they played a role in the nucleus. Therefore, DlB3s might be involved in complex plant hormone signal transduction pathways during longan SE and zygotic embryo development.

Bilayer magnetic-plasmonic satellite nanoassemblies for SERS detection of tobramycin with exonuclease amplification.

Nanoscale assemblies designed for trace analyte detection typically require a complex fabrication process. Here, we prepare magnetic nanoparticle (Fe3O4)-gold nanoparticle (AuNP)-gold nanostar (AuNS) bilayer magnetic-plasmonic satellite nanoassemblies (BMPSNs) for ultrasensitive detection of tobramycin (TOB). BMPSNs are constructed through seed-mediated growth and complementary DNA hybridization, combining magnetic separation and surface-enhanced Raman scattering (SERS) activities. AuNP is in situ growth on the surface of Fe3O4 to form the monolayer satellite assemblies. Partially complementary double-stranded DNA (DNA1/DNA2) is modified onto the surface of the first layer satellite AuNP. TOB aptamer (Apt) and fully complementary DNA (cDNA) form the duplex DNA. In the presence of TOB, cDNA of TOB Apt is replaced by TOB/TOB Apt, which can hybridize with DNA2 modified on the surface of Fe3O4@AuNP-DNA1/DNA2 and further triggers exonuclease III cyclic amplification to obtain Fe3O4@AuNP-DNA1. Finally, Fe3O4@AuNP-DNA1 can assemble with AuNS@4-MBA-DNA3 through DNA hybridization to form BMPSNs. Thanks to excellent magnetic separation, exonuclease amplification and huge SERS enhancement of multiple hot spots, the limit of detection can achieve as low as 0.44 fg/mL of TOB, which is more sensitive than the previously reported methods. In addition, this method can be applied to TOB detection in actual samples with good recoveries and without interference by other antibiotics. The proposed method can be easily extended to sensitive detection of other targets by replacing the corresponding aptamers, paving a new avenue for food safety and environment monitoring.

A surface-enhanced Raman scattering aptasensor for Escherichia coli detection based on high-performance 3D substrate and hot spot effect.

A surface-enhanced Raman scattering (SERS) aptasensor was established for highly sensitive and selective detection of Escherichia coli (E. coli). Chitosan hydrogel modified with E. coli aptamer (Apt) functionalized silver nanoparticles was constructed as a SERS 3D substrate for specific bacteria enrichment, while the Raman signaling molecule 4-mercaptobenzoic acid and E. coli Apt modified gold nanostars were prepared for the sensitive quantification of E. coli. The aptasensor exhibits intense electromagnetic field enhancement in multiple hot spot regions, including the spikes and the gap between adjacent nanostars and that between gold nanostars and silver nanoparticles. Due to the hot spot effect coupled with the selective recognition ability, a detection limit of 3.46 CFU/mL with a wide dynamic linearized range from 3.2 × 101 to 3.2 × 107 CFU/mL could be achieved without other non-target bacteria interference. Moreover, this SERS aptasensor was applied to detect E. coli in actual samples with a good recovery rate (>90%). Therefore, the developed SERS aptasensor paves a new avenue for the detection in the field of food safety and environmental pollution by replacing the corresponding aptamers.

An ultrasensitive and dual-recognition SERS biosensor based on Fe3O4@Au-Teicoplanin and aptamer functionalized Au@Ag nanoparticles for detection of Staphylococcus aureus.

An ultrasensitive and dual-recognition surface-enhanced Raman scattering (SERS) biosensor for Staphylococcus aureus (S. aureus) was constructed, which was based on teicoplanin (Tcp) functionalized gold-coated magnet nanoparticles (Fe3O4@Au-Tcp NPs) as capture probe and S. aureus aptamer (Apt) functionalized silver coated gold nanoparticles (Au@Ag-DTNB-Apt NPs) as signal probe. Both Au NPs and Au@Ag NPs were prepared by a green synthesis method. Especially, the synthesis method of Au@Ag NPs reduced by chitosan (CS) was first reported in this work. Due to the great SERS enhancement based on the hot spot effect between Au NPs and Au@Ag NPs, and the dual-recognition ability based on Tcp and Apt, the SERS biosensor was ultrasensitive and specific. A detection limit of 1.09 CFU mL-1 with a broad dynamic linear (7.6 × 101-7.6 × 107 CFU mL-1) was achieved within 50 min without interference by other bacteria. Moreover, the SERS biosensor could be applied for detection of S. aureus in milk and orange juice samples. This study provides a green, rapid and ultrasensitive method to detect S. aureus, and also explores the high utilization value of CS and Tcp, which has a broad application prospect in detection of pathogenic bacteria.

A fluorescence and surface-enhanced Raman scattering dual-mode aptasensor for rapid and sensitive detection of ochratoxin A.

A fluorescence and surface-enhanced Raman scattering (FL-SERS) dual-mode aptasensor was established for sensitive and rapid detection of Ochratoxin A (OTA). This aptasensor was assembled by the hybridization of OTA aptamer (OTA Apt) modified gold nanostars (Apt-AuNSs) and Cy3 modified complementary DNA functionalized gold nanospheres (cDNA-AuNPs). The aptasensor displays a low FL signal due to the proximity of Cy3 to AuNSs, and a high SERS signal due to the "hot spot" effect generated by the nano-gap between AuNSs and AuNPs. In the presence of OTA, the preferential combination of OTA Apt and OTA results in a low SERS signal. Meanwhile, cDNA-AuNPs are released from the hybrid complex, leading to the recovery of the FL signal. The aptasensor has a low detection limit of 0.17 ng/mL (the detection range is 1-100 ng/mL) in FL mode and 1.03 pg/mL (the detection range is 5-250 pg/mL) in SERS mode. Furthermore, this aptasensor exhibits high specificity and good interferent resistance, which can discriminate OTA from other mycotoxins. Moreover, this aptasensor can be used for OTA detection in coffee and wine samples with good recovery rates. Unlike single-signal aptasensors, this dual-mode aptasensor holds exquisite properties such as high reliability, great detection flexibility and good anti-interference ability.