Bacillus simplex treatment promotes soybean defence against soybean cyst nematodes: A metabolomics study using GC-MS.

We aimed to profile the metabolism of soybean roots that were infected with soybean cyst nematodes and treated with Bacillus simplex to identify metabolic differences that may explain nematode resistance. Compared with control soybean roots, B. simplex-treated soybean roots contained lower levels of glucose, fructose, sucrose, and trehalose, which reduced the nematodes' food source. Furthermore, treatment with B. simplex led to higher levels of melibiose, gluconic acid, lactic acid, phytosphingosine, and noradrenaline in soybean roots, which promoted nematocidal activity. The levels of oxoproline, maltose, and galactose were lowered after B. simplex treatment, which improved disease resistance. Collectively, this study provides insight into the metabolic alterations induced by B. simplex treatment, which affects the interactions with soybean cyst nematodes.

[Responses of shallow soil water content in Artemisia ordosica community to different rainfall patterns]. / æ²¹è’¿çŒä¸›ç¾¤è½æµ å±‚åœŸå£¤æ°´åˆ†å¯¹ä¸åŒé™é›¨æ ¼å±€çš„å“åº”.

The shrub species, Artemisia ordosica, commonly occurs in the eastern Hobq desert. Here, we used a micrometeorological observation system to continuously monitor the rainfall and soil water content in 0-10, 10-30, and 30-50 cm soil layers during the growing season from 2016 to 2018. The dynamic spatial and temporal changes in soil water content under different rainfall patterns were examined, and the replenishing effects of rainfall events on soil water content and water infiltration characteristics were analyzed. The results showed that soil water content of the surface layer in the A. ordosica community had significant seasonal and vertical variation under rainfall fluctuation. Rainfall amount and soil water content before rain were the main factors controlling soil water replenishment and infiltration. The soil surface layer (0-10 cm) was sensitive to rainfall, and the rainfall of 3.8 mm began to replenish this layer. The responses of 10-30 cm soil layer to rainfall was slower, more than 8.6 mm rainfall being needed for effective replenishment. The response of the 30-50 cm soil layer to rainfall was even more delayed, and replenishment at this depth could not be achieved until the rainfall exceeded 11.8 mm. The water infiltration rate increased with rainfall amount and decreased with soil depth, while water infiltration depth was positively correlated with the rainfall amount and soil water content before rainfall. During the study period, rainfall of <10 mm occurred predominantly, accounting for 78.4% of the total rainfall events. The rainfall mainly replenished soil layer above 30 cm, and the replenishment of deep soil was very limited, which was not conducive to the growth of deep-rooted species. Therefore, rainfall patterns directly affected the composition, distribution, and succession of plant communities in this area.

[Variations of soil respiration and its temperature sensitivity in the reversion process of desertification in the eastern Hobq Desert, China]. / åº“å¸ƒé½ä¸œç¼˜æ²™æ¼ åŒ–é€†è½¬è¿‡ç¨‹ä¸­åœŸå£¤å‘¼å¸åŠå ¶æ¸©åº¦æ•æ„Ÿæ€§å˜åŒ–.

To clarify the effects of desertification reversal on soil respiration rate (Rs) and its temperature sensitivity (Q10), five different reversal stages were selected: mobile dune, semi-fixed sandland, algae crust fixed sandland, lichen crust fixed sandland, and moss crust fixed sandland in the eastern Hobq Desert. Rs at different stages were measured by static chamber-gas chromatography and the Q10 was calculated. We analyzed the effects of environmental factors on Rs. The results showed that Rs gradually increased with sand fixation and vegetation succession: moss crust fixed sandland (0.78 µmol·m-2·s-1)> lichen crust fixed sandland (0.67 µmol·m-2·s-1)> algae crust fixed sandland (0.46 µmol·m-2·s-1)> semi-fixed sandland (0.42 µmol·m-2·s-1)> mobile dune (0.29 µmol·m-2·s-1). The Rs of growing season was higher than that of non-growing season. Q10 of Rs at different reversal stages followed the order: mobile dune (3.28)> semi-fixed sandland (2.93)> algae crust fixed sandland (2.54)> lichen crust fixed sandland (1.91)> moss crust fixed sandland (1.84). The Q10 of non-growing season was higher than that of growing season. There was positive correlation between Rs and soil temperature. Rs of mobile and semi-fixed sand was positively correlated with soil water content, but not in other three fixed sandlands. Rs was correlated with soil total nitrogen, organic carbon, bulk density, porosity, quantity of bacteria, quantity of actinomycetes and quantity of fungi. Our results indicated that in the process of desertification reversal, the increases of soil organic carbon and nitrogen content and the abundance of microbes, the improvement of soil texture and the accumulation of plant biomass could dramatically enhance soil respiration and reduce its temperature sensitivity, which were the main driving forces to change carbon cycle of desert soil, and mediate the effects of soil water on soil respiration.

SNARE proteins SYP22 and VAMP727 negatively regulate plant defense.

Soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs) are the key regulators control trafficking of cargo proteins to their final destinations and plays key role in plant development; however, their roles in plant defense remain largely unknown. R-SNARE VAMP727 and Qa-SNARE SYP22 were previously reported to associate with vacuolar protein deposition and brassinosteroids (BRs) receptor BRI1 plasma membrane targeting. Here, we identified that VAMP727 and SYP22 are induced by infection of root-knot nematode (RKN), a plant pathogen, which cause severe growth defect and yield loss. Furthermore, decreased root-knot nematode (RKN) invasion, growth and disease index were observed in bri1-5 and SYP22ND, a SYP22 negative dominant mutants when compared to control plants. Overall, our results suggest that VAMP727-SYP22 SNARE complexes regulate plant defense might be via control of abundances of BRI1 on the plasma membrane.

Greenhouse gas fluxes at different growth stages of biological soil crusts in eastern Hobq desert, China.

We analyzed greenhouse gas fluxes at the different growth stages of algae and lichen crusts in fixed sand with mobile dune as control in the eastern Hobq Desert, China, using the spatio-temporal substitution method. We explored the correlation of these fluxes with environmental factors and with biological soil crust growth. The results showed that variation of CO2 fluxes followed the order: lichen crust (128.5 mg·m-2·h-1) > algae crust (70.2 mg·m-2·h-1) > mobile dune (48.2 mg·m-2·h-1). CH4 absorption rates were in the following order: lichen crust (30.4 µg·m-2·h-1) > algae crust (21.2 µg·m-2·h-1) > mobile dune (18.2 µg·m-2·h-1). The N2O fluxes were in the following order: lichen crust (6.6 µg·m-2·h-1) > algae crust (5.4 µg·m-2·h-1) > mobile dune (2.5 µg·m-2·h-1). CO2 emission had obvious seasonal variation, with higher emission in the growing season. CH4 and N2O fluxes had no seaonal variation. CH4 absorption mainly occurred in the growing season and N2O emission mainly occurred in non-growing season. Contents of soil total nitrogen and organic carbon and the abundance of microorganisms were important factors affecting greenhouse gas fluxes. Hydrothermic factors were important for soil CO2 emission, but not for CH4 and N2O fluxes. The cumulative greenhouse gas emissions were gradually increased with vegetation restoration and the development of biological soil crust. The global warming potential increased following an order: lichen crust (1135.7 g CO2-e·m-2·a-1) > algae crust (626.5 g CO2-e·m-2·a-1) > mobile dune (422.7 g CO2-e·m-2·a-1).

[Characteristics of soil microorganisms and soil nutrients in different sand-fixation shrub plantations in Kubuqi Desert, China]. / åº“å¸ƒé½æ²™æ¼ ä¸åŒäººå·¥å›ºæ²™çŒæœ¨æž—åœŸå£¤å¾®ç”Ÿç‰©é‡ä¸ŽåœŸå£¤å »åˆ†ç‰¹å¾.

Three types of sand-fixation shrub plantations, including Artemisia ordosica + Hedysarum fruticosum, Caragana korshinskii and Salix psammophila, were selected in the eastern area of Kubuqi Desert to study the changes in soil microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN), quantities of soil microorganisms, contents of soil nutrients and the relations among these variables under the different plantation types and shifting sandy land. The restoration effects of each plantation type on soil quality were assessed by synthetic index method. The results showed that the contents of soil organic matter, total nitrogen and phosphorus, and available nitrogen and phosphorus under different plantations were all significantly greater than those under shifting sandy land, and the order of increase was A. ordosica + H. fruticosum ＞ C. korshinskii ＞ S. psammophila. The soil nutrient contents decreased with the increase of soil depth under all plantation types. The quantities of soil microorganisms and the contents of soil MBC and MBN under the plantations were higher at different degrees than those under shifting sandy land. MBC, MBN and the relative numbers of bacteria under A. ordosica+H. fruticosum plantation were higher than those under C. korshinskii plantation and S. psammophila plantation. The relative numbers of fungi and actinobacteria decreased in the order of C. korshinskii ＞ S. psammophila ＞ A. ordosica + H. fruticosum. The relative number of bacteria, MBC and MBN under the plantations were mainly affected by the contents of soil organic matter, total nitrogen, total phosphorus, available nitrogen, available phosphorus, as well as C/N, and the relative numbers of actinobacteria and fungi were primarily affected by the contents of soil total phosphorus, available nitrogen and available phosphorus. Soil quality was ranked in the order of A. ordosica + H. fruticosum ＞ C. korshinskii ＞ S. psammophila ＞ shifting sandy land. These results demonstrated that different sand-fixation shrub plantations could improve the quality of the desert soil and the A. ordosica + H. fruticosum plantation was the best for soil restoration and quality improvement in the desert.

Integrative View of the Diversity and Evolution of SWEET and SemiSWEET Sugar Transporters.

Sugars Will Eventually be Exported Transporter (SWEET) and SemiSWEET are recently characterized families of sugar transporters in eukaryotes and prokaryotes, respectively. SemiSWEETs contain 3 transmembrane helices (TMHs), while SWEETs contain 7. Here, we performed sequence-based comprehensive analyses for SWEETs and SemiSWEETs across the biosphere. In total, 3,249 proteins were identified and ≈60% proteins were found in green plants and Oomycota, which include a number of important plant pathogens. Protein sequence similarity networks indicate that proteins from different organisms are significantly clustered. Of note, SemiSWEETs with 3 or 4 TMHs that may fuse to SWEET were identified in plant genomes. 7-TMH SWEETs were found in bacteria, implying that SemiSWEET can be fused directly in prokaryote. 15-TMH extraSWEET and 25-TMH superSWEET were also observed in wild rice and oomycetes, respectively. The transporters can be classified into 4, 2, 2, and 2 clades in plants, Metazoa, unicellular eukaryotes, and prokaryotes, respectively. The consensus and coevolution of amino acids in SWEETs were identified by multiple sequence alignments. The functions of the highly conserved residues were analyzed by molecular dynamics analysis. The 19 most highly conserved residues in the SWEETs were further confirmed by point mutagenesis using SWEET1 from Arabidopsis thaliana. The results proved that the conserved residues located in the extrafacial gate (Y57, G58, G131, and P191), the substrate binding pocket (N73, N192, and W176), and the intrafacial gate (P43, Y83, F87, P145, M161, P162, and Q202) play important roles for substrate recognition and transport processes. Taken together, our analyses provide a foundation for understanding the diversity, classification, and evolution of SWEETs and SemiSWEETs using large-scale sequence analysis and further show that gene duplication and gene fusion are important factors driving the evolution of SWEETs.

Descriptions of two new record species of Scutellonema (Nematoda: Tylenchida) from China.

From 2011 to 2012, we collected Scutellonema commune from the rhizosphere soil of coconut (cocos nucifera L.) and Scutellonema magniphasma from the rhizosphere soil of Rosa chinensis in Shenyang, China. S. commune was characterized by rounded scutella, which was varied from two annules anterior to the anus and five annules posterior. The lateral field was not areolated at the level of scutella. S. magniphasma was characterized by varying scutellum, about 7.0 µm in diameter, in position from four annules posterior to four annules anterior to the anus, and areolated at the level of the scutellum.

Description of a new Pratylenchus species from China (Tylenchida, Pratylenchidae).

Pratylenchus ekrami from maize (Zea mays) roots in Shenyang and luffa (Luffa cylindrica) roots in Dalian, China, are described in this paper. Nematodes from the two areas were identified consistently, and were characterized by a heavy cephalic sclerotization, extending posteriorly up to two body annuli, stylet 11-13 µm long, elongating conoid tail, and becoming thinner from vulva. Males were not found. Pratylenchus ekrami is close to Pratylenchus vulnus, but the most critical characteristics between the two species were the number of lip annuli, stylet size, and shape of stylet knobs. This species is the first reported in China. Pratylenchus ekrami from maize (Zea mays) roots in Shenyang and luffa (Luffa cylindrica) roots in Dalian, China, are described in this paper. Nematodes from the two areas were identified consistently, and were characterized by a heavy cephalic sclerotization, extending posteriorly up to two body annuli, stylet 11-13 µm long, elongating conoid tail, and becoming thinner from vulva. Males were not found. Pratylenchus ekrami is close to Pratylenchus vulnus, but the most critical characteristics between the two species were the number of lip annuli, stylet size, and shape of stylet knobs. This species is the first reported in China.