Mitogen-activated protein kinase (MAPK) cascades play important roles in mediating biotic and abiotic stress responses. In plants, MAPKs are classified into four major groups (A-D) according to their sequence homology and conserved phosphorylation motifs. Compared with well-studied MAPKs in groups A and B, little is known about group C. In this study, we functionally characterised a stress-responsive group C MAPK gene (GhMPK2) from cotton (Gossypium hirsutum). Northern blot analysis indicated that GhMPK2 was induced by abscisic acid (ABA) and abiotic stresses, such as NaCl, PEG, and dehydration. Subcellular localization analysis suggested that GhMPK2 may activate its specific targets in the nucleus. Constitutive overexpression of GhMPK2 in tobacco (Nicotiana tabacum) conferred reduced sensitivity to ABA during both seed germination and vegetative growth. Interestingly, transgenic plants had a decreased rate of water loss and exhibited enhanced drought and salt tolerance. Additionally, transgenic plants showed improved osmotic adjustment capacity, elevated proline accumulation and up-regulated expression of several stress-related genes, including DIN1, Osmotin and NtLEA5. β-glucuronidase (GUS) expression driven by the GhMPK2 promoter was clearly enhanced by treatment with NaCl, PEG, and ABA. These results strongly suggest that GhMPK2 positively regulates salt and drought tolerance in transgenic plants.

The accurate discrimination of microRNAs (miRNAs) with highly similar sequences would greatly facilitate the screening and early diagnosis of diseases. In the present work, a locked nucleic acid (LNA)-modified probe was designed and used for α-hemolysin (α-HL) nanopore to selectively and specifically identify miRNAs. The hybridization of the LNA probe with the target miRNAs generated unique long-lived signals in the nanopore thus facilitated an accurate discrimination of miRNAs with similar sequences, even a single-nucleotide difference. Furthermore, the developed nanopore-based analysis with LNA probe could selectively detect target miRNAs in a natural serum background. This selective and sensitive approach may be highly valuable in the detection of clinically relevant biomarkers in complex samples.

Sensitive detection of cancer cells at extremely low concentrations would greatly facilitate the screening and early diagnosis of cancer. Herein, we present a novel nanopore-based strategy for ultrasensitive detection of Ramos cells (human Burkitt's lymphoma cells), by combining the enzymatic signal amplification with an aerolysin nanopore sensor. In this assay, an aptamer for Ramos cells was prehybridized with a short complementary DNA. The presence of target cells causes the target-aptamer complex to unwind to free the complementary DNA, which would subsequently trigger the enzymatic cycling amplification. This process eventually generated a large number of output DNA, which could quantitatively produce characteristic current events when translocated through aerolysin. The proposed method exhibits excellent sensitivity, and as few as 5 Ramos cells could be detected. With good selectivity, the approach can allow for the determination of cancer cells in human serum, offering a powerful tool for biomedical research and clinical diagnosis.

Small heat shock proteins (sHSPs) play an important role in the cellular defense of prokaryotic and eukaryotic organisms against a variety of internal and external stressors. In this study, a cDNA clone encoding a member of the α-crystallin/sHSP family, termed AccHsp27.6, was isolated from Apis cerana cerana. The full-length cDNA is 1,014 bp in length and contains a 708-bp open reading frame encoding a protein of 236 amino acids with a calculated molecular weight of 27.6 kDa and an isoelectric point of 7.53. Seven putative heat shock elements and three NF-κB binding sites were present in the 5′-flanking region, suggesting a possible function in immunity. A semi-quantitative RT-PCR analysis indicated that AccHsp27.6 was expressed in all tested tissues and at different developmental stages. Furthermore, expression of the AccHsp27.6 transcript was induced by exposure to heat shock, H 2 O 2 , a number of different chemicals (including SO 2 , formaldehyde, alcohol, acetone, chloroform, and the pesticides phoxime and acetamiprid), and the microbes Staphylococcus aureus and Micrococcus luteus. In contrast, the mRNA expression could be repressed by CO 2 , the pesticides pyriproxyfen and cyhalothrin, and the microbes Bacillus subtilis and Pseudomonas aeruginosa. Notably, the recombinant AccHsp27.6 protein exhibited significant in vitro molecular chaperone activity and antimicrobial activity. Taken together, these results suggest that AccHsp27.6 might play an important role in the response to abiotic and biotic stresses and in immune reactions.

Mitogen‐activated protein kinase (MAPK) cascades play important roles in mediating pathogen responses and reactive oxygen species signaling. In plants, MAPKs are classified into four major groups (A–D). Previous studies have mainly focused on groups A and B, but little is known about group C. In this study, we functionally characterized a stress‐responsive group C MAPK gene (GhMPK2) from cotton. Northern blot analysis indicated that GhMPK2 was induced not only by signaling molecules, such as ethylene and methyl jasmonate, but also by methyl viologen‐mediated oxidative stress. Transgenic tobacco (Nicotiana tabacum) plants that overexpress GhMPK2 displayed enhanced resistance to fungal and viral pathogens, and the expression of the pathogenesis‐related (PR) genes, including PR1, PR2, PR4, and PR5, was significantly increased. Interestingly, the transcription of 1‐aminocyclopropane‐1‐carboxylic acid synthase (ACS) and 1‐aminocyclopropane‐1‐carboxylic acid oxidase (ACO) was significantly upregulated in transgenic plants, suggesting that GhMPK2 positively regulates ethylene synthesis. Moreover, overexpression of GhMPK2 elevated the expression of several antioxidant enzymes, conferring on transgenic plants enhanced reactive oxygen species scavenging capability and oxidative stress tolerance. These results increased our understanding of the role of the group C GhMPK2 gene in multiple defense‐signaling pathways, including those that are involved in responses to pathogen infection and oxidative stress.