A large presence/absence variation in the promotor of the ClLOG gene determines trichome elongation in watermelon.

KEY MESSAGE: The ClLOG gene encoding a cytokinin riboside 5'-monophosphate phosphoribohydrolase determines trichome length in watermelon, which is associated with its promoter variations. Trichomes, which are differentiated from epidermal cells, are special accessory structures that cover the above-ground organs of plants and possibly contribute to biotic and abiotic stress resistance. Here, a bulked segregant analysis (BSA) of an F2 population with significant variations in trichome length was undertaken. A 1.84-Mb candidate region on chromosome 10 was associated with trichome length. Resequencing and fine-mapping analyses indicated that a 12-kb structural variation in the promoter of Cla97C10G203450 (ClLOG) led to a significant expression difference in this gene in watermelon lines with different trichome lengths. In addition, a virus-induced gene silencing analysis confirmed that ClLOG positively regulated trichome elongation. These findings provide new information and identify a potential target gene for controlling multicellular trichome elongation in watermelon.

K fertilizer alleviates N2O emissions by regulating the abundance of nitrifying and denitrifying microbial communities in the soil-plant system.

Potassium (K) fertilizer additions can result in high crop yields of good quality and low nitrogen (N) loss; however, the interaction between K and N fertilizer and its effect on N2O emissions and associated microbes remain unclear. We investigated this in a pot experiment with six fertilizer treatments involving K and two sources of N, using agricultural soil from the suburbs of Wuhan, central China. The aim was to determine the effects of the interaction between K and different forms of N on the N2O flux and the abundance of nitrifying and denitrifying microbial communities, using static chamber-gas chromatography and high-throughput sequencing methods. Compared with no fertilizer control (CK), the addition of nitrate fertilizer (NN) or ammonia fertilizer (AN) or K fertilizer significantly increased N2O emissions. However, the combined application (NNK) of K and NN significantly reduced the average N2O emissions by 28.3%, while the combined application (ANK) of K and AN increased N2O emissions by 22.7%. The abundance of nitrifying genes amoA in ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) changed in response to N and/or K fertilization, but the denitrifying genes narG, nirK and norl were strongly correlated with N2O emissions. This suggests that N or K fertilizer and their interaction affect N2O emissions mainly by altering the abundance of functional genes of denitrifying microbes in the soil-plant system. The genera Paracoccus, Rubrivivax and Geobacter as well as Streptomyces and Hyphomicrobium play an important role in N2O emissions during denitrification with the combined application of N and K.

Straw with different fermentation degrees mediate Se/Cd bioavailability by governing the putative iron reducing bacteria.

Straw returning is a crucial agronomic practice in fields due to its various benefits. However, effects and mechanisms of straw with different fermentation degrees on Se and Cd bioavailability have not been sufficiently investigated. In this study, straw with different fermentation degrees were applied to a Cd-contaminated seleniferous soil to investigate their effects on Se and Cd bioavailability. Results revealed that the effects of straw application on Se/Cd bioavailability in soil depended on the fermentation degrees of straw. Both original and slightly fermented straw had pronounced impacts on microbial iron reduction compared to fully fermented straw, and thus led to a significant increase in Se and Cd bioavailability. The linear discriminant analysis effect size (LEfSe) showed that norank_f_Symbiobacteraceae, Micromonospora, WCHB1-32, Ruminiclostrdium, and Cellulomonas were the major biomarkers at genus level in straw application soils, additional network analysis and random forest analysis suggested that Ruminiclostrdium and Cellulomonas might be implicated in microbial iron reduction. Furthermore, the microbial iron reduction had negative effects on mineral-associated Se with coefficient of -0.81 and positive effects on mineral-associated Cd with coefficient of 0.72, while Mn fractions exhibited positive effects on mineral-associated Se with a coefficient of 0.53 and negative effects on mineral-associated Cd. In conclusion, straw with different fermentation degrees governed Se and Cd mobility by regulating abundance of Ruminiclostrdium and Cellulomonas, subsequently affecting Fe and Mn fractions and consequently influencing Se and Cd bioavailability.

Enhancement patterns of potassium on nitrogen transport and functional genes in cotton vary with nitrogen levels.

The application of potassium (K) in conjunction with nitrogen (N) has been shown to enhance N use efficiency. However, there is still a need for further understanding of the optimal ratios and molecular regulatory mechanisms, particularly in soil-cotton systems. Here, a field trial was conducted, involving varying rates of N and K, alongside pot and hydroponic experiments. The objective was to assess the impact of N-K interaction on the absorption, transport and distribution of N in cotton. The results showed that K supply at 90 and 240 kg ha-1 had a beneficial impact on N uptake and distribution to both seed and lint, resulting in the highest N use efficiency ranging from 22% to 62% and yield improvements from 20% to 123%. The increase in stem and root diameters, rather than the quantify of xylem vessels and phloem sieve tubes, facilitated the uptake and transport of N due to the provision of K. At the molecular level, K supply upregulated the expression levels of genes encoding GhNRT2.1 transporter and GhSLAH3 channel in cotton roots to promote N uptake and GhNRT1.5/NPF7.3 genes to transport N to shoot under low-N conditions. However, under high-N conditions, K supply induced anion channel genes (GhSLAH4) of roots to promote N uptake and genes encoding GhNRT1.5/NPF7.3 and GhNRT1.8/NPF7.2 transporters to facilitate NO3- unloading from xylem to mesophyll cell in high-N plants. Furthermore, K supply resulted in the upregulation of gene expression for GhGS2 in leaves, while simultaneously downregulating the expression of GhNADH-GOGAT, GhGDH1 and GhGDH3 genes in high-N roots. The enzyme activities of nitrite reductase and glutamine synthetase increased and glutamate dehydrogenase decreased, but the concentration of NO3- and soluble protein exhibited a significant increase and free amino acid decreased in the shoots subsequent to K supply.

Effects of land use on soil microplastic distribution adjacent to Danjiangkou reservoir, China.

As a new type of pollutant, microplastics (MPs) are an increasingly prominent threat to terrestrial ecosystems. However, the distribution, sources and influencing factors of MPs need to be further studied, especially in reservoir surrounding soil, a hot zone for MPs accumulation and a source of MPs in the watershed. Here, we detected MPs in 120 soil samples collected around Danjiangkou reservoir, with their amount ranging from 645 to 15,161 items/kg. The topsoil layer at 0-20 cm had lower levels of MPs (mean 3989 items/kg) than subsoils at 20-40 cm (mean 5620 items/kg). The most commonly detected types of MPs were polypropylene (26.4%) and polyamide (20.2%), with sizes ranging from 0.05 to 0.5 mm. With regard to shape, most MPs (67.7%) were fragmented, while fibers make up 25.3% of the MPs. Further analysis revealed that the number of villages had the highest driving force for the abundance of MPs with 51%, followed by pH 25% and land use types 10%. The water and sediment of reservoirs are important sources of agricultural soil microplastics. Paddy lands showed higher microplastics levels than orchards and dry croplands. The polymer risk index indicated that the agricultural soil near Danjiangkou reservoir had the highest MPs risk. This study highlights the importance of assessing MPs contamination in the agroecosystems surrounding reservoirs and provides valuable insight into clarify the ecological risks of MPs in the reservoir area.

[Distribution Characteristics and Risk Assessment of Microplastics in Soil in Danjiangkou Reservoir Area of South-to-North Water Diversion Project].

To explore the occurrence characteristics and influencing factors of microplastics in soil in the Danjiangkou Reservoir area, this study collected soil samples from orchards, dryland, paddy fields, and wetland and identified microplastics in soil via density sorting, microscope observation, and Raman spectrometry. The results showed that microplastics were detected in 64 samples collected in the study area, and the abundance ranged from 645 to 15161 n·kg-1. The spatial distribution of microplastics in the bottom of the reservoir was higher than those in the middle and head of the reservoir, and the abundance of microplastics in the surface soil(0-20 cm) was significantly lower than that in the bottom soil(20-40 cm). The main types of microplastics were polypropylene(26.4%) and polyamide(20.2%), the particle size was mainly concentrated between 50-500 µm(75%), and the common shape was fragments(66.2%). Correlation analysis showed that soil microplastic abundance was closely related to land use, distance from water and housing, population density, and soil properties. From the perspective of microplastic pollution risk, 72.1% of the region's microplastic polymer risk index was at level Ⅲ and level Ⅳ, and there was a certain risk of microplastic pollution in the Danjiangkou Reservoir area. The results of this study can provide support for risk assessment of microplastics.

Gold nanorods conjugated with biocompatible zwitterionic polypeptide for combined chemo-photothermal therapy of cervical cancer.

Combined chemo-photothermal therapy of gold nanorods (GNRs) for cancer treatment shows better therapeutic efficiency than mono-chemotherapy, which has gained worldwide interests of scientists and clinician in both laboratory and clinic application. However, high cytotoxicity, declined delivery efficiency, and unsatisfactory therapy effect of the GNRs are still challenging in anti-cancer treatment. Herein, a series of pH-sensitively zwitterionic polypeptide conjugated GNRs were synthesized via a gold-thiol interaction for combination of chemo-photothermal therapy in cervical cancer treatment. The acid-labile hydrazone bond was utilized to incorporate the doxorubicin (DOX) for pH-sensitive drug release under tumoral environment. The as prepared GNRs conjugates demonstrated pH-triggered surface charge conversion from negative to positive when transporting from blood circulation to tumor extracellular environment, which can facilitate the cellular uptake via electrostatic interaction. After cellular internalization, the drug release was promoted by cleavage of the hydrazone in GNRs conjugates under cancer intracellular acid environment. As the effective near-infrared (NIR) photothermal materials, the as prepared GNRs conjugates can absorb NIR photo energy and convert it into heat under irradiation, which can efficiently kill the tumor cells. In cell assay, the GNRs conjugates displayed excellent biocompatibility against normal cell, enhanced cancer cell uptake, and remarkable cancer cell killing effects. In HeLa tumor-bearing mice, the GNRs conjugates demonstrated enhanced tumor inhibition efficacy by combination of chemo-photothermal therapy.

Phosphorus spatial distribution and pollution risk assessment in agricultural soil around the Danjiangkou reservoir, China.

The phosphorus (P) content in agricultural soils in catchments of lakes or rivers is an important issue because P is both an essential nutrient for high plant yields and a major contributor to eutrophication of water bodies. Thus, we have assessed the spatial distribution of soil P, impacts of environmental factors on its spatial variation, and associated pollution risks, in farmland around the Danjiangkou Reservoir, China. A total of 217 sites were sampled, including 121, 44 and 52 in dry cropland, paddy land and orchards, respectively. Total phosphorus (TP) contents in the sampled soils ranged from 0.230 to 1.893 g kg-1 and Olsen-P (a measure of available P) from 0.38 to 176 mg kg-1. Soil TP and Olsen-P had moderate and high variability, with coefficients of variation of 40% and 115%, respectively. Geostatistical analysis showed that both TP and Olsen-P had positive nugget effects, but TP had stronger spatial autocorrelations than Olsen-P (nugget-to-sill ratios: 22 and 50%, respectively). Total P was significantly influenced by temperature, elevation, aspect, soil pH, organic matter and precipitation, while Olsen-P was controlled by aspect and land use. The TP in soil was very similar in dry cropland and orchards (0.64 ±â€¯0.19 and 0.61 ±â€¯0.23 g kg-1, respectively), but substantially lower in paddy land (0.15 ±â€¯0.25 g kg-1). Risks for P loss appeared to be very high, high, moderate and low in approximately 10, 40, 15 and 30% of the farmland in the Danjiangkou reservoir area, respectively.

N2O emissions and product ratios of nitrification and denitrification are altered by K fertilizer in acidic agricultural soils.

Potassium (K) fertilizer plays an important role in increasing crop yield, quality, and nitrogen use efficiency. However, little is known about its environmental impacts, such as its effects on emissions of the greenhouse gas nitrous oxide (N2O). A nitrogen-15 (15N) tracer laboratory experiment was therefore performed in an acidic agricultural soil in the suburbs of Wuhan, central China, to determine the effects of K fertilizer on N2O emissions and nitrification/denitrification product ratios under N fertilization. During 15-d incubation periods with a fixed initial N concentration (80 mg kg-1), K application increased average N2O emission rates significantly (1.6-10.8-fold) compared to the control treatment. N2O emissions derived from nitrification and denitrification both increased in K-treated soil, and denitrification contributed more to the increase; its contribution ratio rose from 32% without K fertilizer to 53% with 300 mg kg-1 of K applied. The increase in N2O emissions under K fertilization is probably due to an increase in the activity of denitrifying microorganisms and acid-resistant nitrifying microorganisms caused by higher K+ concentrations and lower soil pH. Combined treatment with potassium chloride (KCl) and N fertilizer produced lower N2O emissions than combined treatment with potassium sulfate (K2SO4) and N fertilizer during 15-d incubation periods. Our results imply that there are significant interaction effects between N fertilizers and K fertilizers on N2O emissions. In particular, combining N fertilizers with fertilizers that reduce soil acidity or contain Cl or K ions may significantly affect agricultural N2O emissions.