Six genes, which encode enzymes involved in ascorbic acid (AsA) biosynthesis, including guanosine diphosphate (GDP)-mannose pyrophosphorylase (GMP), GDP-mannose-3',5'-epimerase (GME), GDP-galactose guanylyltransferase (GGT), L-galactose-1-phosphate phosphatase (GPP), L-galactose dehydrogenase (GDH) and L-galactono-1,4-lactone dehydrogenase (GLDH) were transformed into Arabidopsis thaliana, to evaluate the contribution of each gene to AsA accumulation. Additionally, two combinations, GGT-GPP and GGT-GLDH, were co-transformed into Arabidopsis with a reliable double-gene transformation system. AsA content of GGT transgenic lines was 2.9-fold higher as compared to the control, and co-transformation led up to 4.1-fold AsA enhancement. These results provided further evidence that GGT is the key enzyme in plant AsA biosynthesis.Additional key words: GDP-L-galactose guanyltransferase, transgenic plants, vitamin C.

Flexible sensors have great potential in the application of wearable and implantable devices, and conductive hydrogels have been widely used in wearable sensing devices due to their biomimetic structure, biocompatibility, adjustable transparency and stimuli-responsive electrical properties. Conventional conductive hydrogels are prone to be damaged in their application process and lack of long-term reliability. Inspired by natural organisms such as mussels, introduction of self-healing capabilities has been regarded as a promising approach to extend the service life of hydrogel sensing devices. This work

Dicamba, a broad-spectrum and highly efficient herbicide, is an excellent target herbicide for the engineering of herbicide-resistant crops. In this study, a new tetrahydrofolate (THF)-dependent dicamba methyltransferase gene, dmt50, was cloned from the dicamba-degrading strain Rhizorhabdus dicambivorans Ndbn-20. Dmt50 catalyzed the methyl transfer from dicamba to THF, generating the herbicidally inactive product 3,6-dichlorosalicylic acid (3,6-DCSA) and 5-methyl-THF. A dmt50 transgenic Arabidopsis thaliana clearly showed dicamba resistance (560 g/ha, the normal field application rate). However, Dmt50 demethylation activity was inhibited by the product 5-methyl-THF. Mthfr66, encoded by the 5,10-methylene-THF reductase gene mthf r66 could relieve the inhibition by removing 5-methyl-THF in vitro. Compared with expression of dmt50 alone, simultaneous expression of dmt50 and mthfr66 further improved the dicamba resistance (1120 g/ha) of transgenic A. thaliana. This study provides new genes for dicamba detoxification and a strategy for the engineering of dicamba-resistant crops.

Background. Lactobacillus acidophilus not only improves the intestinal fl ora balance but also inhabits the growth of undesirable microorganisms in intestine, which is benefi t to the health of humans and animals. Plackett-Burman and steepest ascent experiment are the rapid and concise ways of screening the main effective factors. This study is aimed to select the main infl uence factors and optimize the medium for Lactobacillus acidophilus by Plackett-Burman experiment and steepest ascent experiment. Material and methods. The ideal carbon source was screened among glucose, maltose, lactose and whey powder, and the ideal nitrogen source was screened among casein hydrolysate, peptone, yeast extract powder, fi sh meal, carbamide, ammonium sulfate and sodium nitrate by single factor experiment. Plackett-Burman and steepest ascent experiment were applied to screen the main effective factors of Lactobacillus acidophilus among peptone, beef extract, yeast extract powder, glucose, K 2 HPO 4 , C 6 H 14 O 7 N 2 , CH 3 COONa, MgSO 4 and Tween-80. Result. The results indicated that glucose (p = 0.01510) as negative factor and K 2 HPO 4 (p = 0.02017) as positive effect were the signifi cant growth factors of Lactobacillus acidophilus, CH 3 COONa (p = 0.09273) as positive effect was an important factor, and the optimized medium was as follows: glucose -21 g/L, K 2 HPO 4 -3.5 g/L, CH 3 COONa -6.5 g/L, peptone -10 g/L, beef extract -8 g/L, yeast extract powder -8 g/L, C 6 H 14 O 7 N 2 -2 g/L, MgSO 4 -0.2 g/L and Tween-80 -1 mL/L when the maximum viable count could achieve 2.72·10 9 cfu/mL. Discussion. The experimental model is reliable and the experimental results are of good stability. Variance analysis is performed to determine the adequacy and signifi cance of the linear model. Thus, Plackett-Burman and steepest ascent experiment improve the veracity of optimization the medium for Lactobacillus acidophilus compared with the previous research.

No abstract