Cloning, Expression, and Functional Analysis of the MYB Transcription Factor SlMYB86-like in Tomato.

MYB transcription factors (TFs) have been shown to play a key role in plant growth and development and are in response to various types of biotic and abiotic stress. Here, we clarified the structure, expression patterns, and function of a MYB TF, SlMYB86-like (Solyc06g071690) in tomato using an inbred tomato line exhibiting high resistance to bacterial wilt (Hm 2-2 (R)) and one susceptible line (BY 1-2 (S)). The full-length cDNA sequence of this gene was 1226 bp, and the open reading frame was 966 bp, which encoded 321 amino acids; its relative molecular weight was 37.05055 kDa; its theoretical isoelectric point was 7.22; it was a hydrophilic nonsecreted protein; and it had no transmembrane structures. The protein also contains a highly conserved MYB DNA-binding domain and was predicted to be localized to the nucleus. Phylogenetic analysis revealed that SlMYB86-like is closely related to SpMYB86-like in Solanum pennellii and clustered with other members of the family Solanaceae. Quantitative real-time PCR (qRT-PCR) analysis revealed that the expression of the SlMYB86-like gene was tissue specific and could be induced by Ralstonia solanacearum, salicylic acid, and jasmonic acid. The results of virus-induced gene silencing (VIGS) revealed that SlMYB86-like silencing decreased the resistance of tomato plants to bacterial wilt, suggesting that it positively regulates the resistance of tomatoes to bacterial wilt. Overall, these findings indicate that SlMYB86-like plays a key role in regulating the resistance of tomatoes to bacterial wilt.

Magnetic relaxation switching immunoassay based on "limited-magnitude" particles for sensitive quantification of aflatoxin B1.

Aflatoxin B1 (AFB1) is a highly toxic and carcinogenic chemical substance that endangers food safety and human health. Magnetic relaxation switching (MRS) immunosensors are utilized in a variety of applications in food analysis due to its resistance to matrix interferences, but they often suffer from magnetic separation-based multi-washing steps and low sensitivity. Herein, we propose novel MRS strategy for the sensitive detection of AFB1 using "Limited-Magnitude" size particles: a single millimeter sized polystyrene spheres (PSmm) and 150 nm superparamagnetic nanoparticles (MNP150). Only a single PSmm is used as the microreactor to enhance all of the magnetic signal on its surface in high concentration by an immune competitive response, successfully preventing signal dilution, which can be transferred by pipette, simplifying the process of separation and washing. The established single polystyrene sphere magnetic relaxation switch biosensor (SMRS) was able to quantify AFB1 from 0.02 to 200 ng/mL with a detection limit of 14.3 pg/mL. SMRS biosensor has been successfully used for the detection of AFB1 in wheat and maize samples, and the results in agreement with high performance liquid chromatography-tandem mass spectrometry (HPLC-MS). Benefiting from high sensitivity and convenient operation, the simple and enzyme-free method is promising in trace small molecules applications.

Multiplexed and DNA amplification-free detection of foodborne pathogens in egg samples: Combining electrical resistance-based microsphere counting and DNA hybridization reaction.

A multiplex and DNA amplification-free sensor based on electrical resistance microsphere counter (ERMC) and DNA hybridization reaction has been developed for simultaneous detection of Listeria monocytogenes, Salmonella Typhimurium, and Staphylococcus aureus in egg samples. In this strategy, magnetic nanoparticles (MNPs) and polystyrene microspheres (PMs) were labeled with DNA probes, the PMs with different sizes (3 µm, 4 µm and 6 µm) were used as multiplex signal reporters due to the high resolution of ERMC. After magnetic separation, the number of unbound PM-probe was related to the concentration of pathogens, and their sizes were attributed to types of pathogens. The limit of detection of this sensor was 20 CFU/mL for Listeria monocytogenes, 89 CFU/mL for Salmonella, and 94 CFU/mL for Staphylococcus aureus, respectively. The DNA amplification-free, simplicity and low-cost of this assay make it a promising tool for the rapid screening of multiple pathogens in food samples.

Signatures of selection in recently domesticated macadamia.

Macadamia is a high value nut crop that is recently domesticated, ideal for testing the effect of artificial selection. Here, we sequence the genome of Hawaiian cultivar 'Kau' and assemble into 794 Mb in 14 pseudo-chromosomes with 37,728 genes. Genome analysis reveals a whole-genome duplication event, occurred 46.8 million years ago. Gene expansions occurred in gene families involves in fatty acid biosynthesis. Gene duplication of MADS-Box transcription factors in proanthocyanidin biosynthesis are relevant for seed coat development. Genome re-sequencing of 112 accessions reveals the origin of Hawaiian cultivars from Mount Bauple in southeast Queensland in Australia. Selective sweeps are detected in macadamia cultivars, including genes involved in fatty acid biosynthesis, seed coat development, and heat stress response. Such strong effects of artificial selection in few generations reveals the genomic basis for 'one-step operation' for clonal crop domestication. The knowledge gained could accelerate domestication of new crops from wild species.

Effect of CPPU on Carbohydrate and Endogenous Hormone Levels in Young Macadamia Fruit.

N-(2-Chloro-4-pyridyl)-N'-phenylurea (CPPU) is a highly active cytokinin-like plant growth regulator that promotes chlorophyll biosynthesis, cell division, and cell expansion. It also increases fruit set and accelerates fruit enlargement. However, there has been no report about the effect of CPPU on fruit development and its physiological mechanism in macadamia. In this study, we investigated the effect of CPPU treatment at early fruit development via foliar spray or raceme soaking at 20 mg·L-1 on fruit set and related physiology in macadamia. Changes in carbohydrate contents and endogenous hormones in leaves, bearing shoots and fruit were also examined. Results showed that CPPU significantly reduced young fruit drop and delayed the wave of fruit drop by 1-2 weeks. The treatment significantly decreased the contents of total soluble sugars and starch in the leaves, but increased them in the bearing shoots and total soluble sugars in the husk (pericarp) and seeds. These findings suggested that CPPU promoted carbohydrate mobilization from the leaves to the fruit. In addition, CPPU increased the contents of indole-3-acetic acid (IAA), gibberellin acid (GA3), and zeatin riboside (ZR) and decreased the abscisic acid (ABA) in the husk. Therefore, CPPU treatment reduced the early fruit drop by increasing carbohydrate availability and by modifying the balance among endogenous hormones.

Thermal sensitive microgels with stable and reversible photoluminescence based on covalently bonded quantum dots.

In this study, thermal sensitive microgels functionalized with carboxyl groups were synthesized directly from hydroxypropyl cellulose (HPC) and acrylic acid (AA) without using any organic solvent. Furthermore, covalently bonded hybrid microgels with novel thermosensitivity in terms of size and fluorescence were fabricated from these HPC-PAA microgels and cysteamine-capped CdTe quantum dots (QDs). The composition of the hybrid microgels were characterized by thermal thermogravimetric analysis (TGA) and coulometric titration. It was verified that the weight percent of CdTe QDs was ca. 40%, and the percent of poly(acrylic acid) varied between 9.0% and 13.6%. Through a systematic study, it was found that both the size and the fluorescent intensity of the microgels decreased as the temperature increased from below the lower critical solution temperature (LCST) to above the LCST of the HPC. Different from most reported cases, it was found that the thermal sensitive alteration of the current hybrid microgels' size and fluorescent intensity are reversible. The novel fluorescent properties are deduced to be related to the structural characteristics of the microgels, i.e., the QDs are covalently bonded to the microgels and the dispersion of QDs in the microgels is spatially homogeneous. As a consequence of this special structure, the refractive indexes of the microgels were changed and the surface defects of the QDs were reduced, and therefore affected the fluorescent properties of the resulting hybrid microgels.