Identification of Cbp1, a c-di-GMP Binding Chemoreceptor in Azorhizobium caulinodans ORS571 Involved in Chemotaxis and Nodulation of the Host Plant

Cbp1, a chemoreceptor containing a PilZ domain was identified in Azorhizobium caulinodans ORS571, a nitrogen-fixing free-living soil bacterium that induces nodule formation in both the roots and stems of the host legume Sesbania rostrata. Chemoreceptors are responsible for sensing signals in the chemotaxis pathway, which guides motile bacteria to beneficial niches and plays an important role in the establishment of rhizobia-legume symbiosis. PilZ domain proteins are known to bind the second messenger c-di-GMP, an important regulator of motility, biofilm formation and virulence. Cbp1 was shown to bind c-di-GMP through the conserved RxxxR motif of its PilZ domain. A mutant strain carrying a cbp1 deletion was impaired in chemotaxis, a feature that could be restored by genetic complementation. Compared with the wild type strain, the Δcbp1 mutant displayed enhanced aggregation and biofilm formation. The Δcbp1 mutant induced functional nodules when inoculated individually. However, the Δcbp1 mutant was less competitive than the wild type in competitive root colonization and nodulation. These data are in agreement with the hypothesis that the c-di-GMP binding chemoreceptor Cbp1 in A. caulinodans is involved in chemotaxis and nodulation

A Legume Host Benefits More from Arbuscular Mycorrhizal Fungi Than a Grass Host in the Presence of a Root Hemiparasitic Plant

In nature, most plants parasitized by root hemiparasites are also colonized by mutualistic arbuscular mycorrhizal (AM) fungi, highlighting the prevalence of this tripartite interaction. AM colonization is generally found to improve the growth of parasitized legumes but has little impact on grass hosts parasitized by root hemiparasites, and the underlying mechanisms are still unclear. In this study, we conducted a pot experiment to test the influence of AM fungus (Glomus mosseae) on the growth and photosynthesis of leguminous Trifolium repens and gramineous Elymus nutans in the presence of a root hemiparasitic plant (Pedicularis kansuensis). The results showed that inoculation with AM fungi significantly improved the growth performance of parasitized legumes via enhancing their nutrient status and photosynthetic capacity, even though a larger P. kansuensis parasitized the legume host in the AM treatment. In contrast, AM colonization slightly improved the shoot DW of grass hosts by suppressing haustoria formation and the growth of P. kansuensis. Our results demonstrated that legume hosts benefit more from AM inoculation than grass hosts in the presence of hemiparasitic plants, and set out the various mechanisms. This study provides new clues for parsing the tritrophic interaction of AM fungi, parasitic plants, and host plants

Soil bacterial community in a photovoltaic system adopted different survival strategies to cope with small-scale light stress under different vegetation restoration modes

Solar photovoltaic (PV) power generation is a major carbon reduction technology that is rapidly developing worldwide. However, the impact of PV plant construction on subsurface microecosystems is currently understudied. We conducted a systematic investigation into the effects of small-scale light stress caused by shading of PV panels and sampling depth on the composition, diversity, survival strategy, and key driving factors of soil bacterial communities (SBCs) under two vegetation restoration modes, i.e., Euryops pectinatus (EP) and Loropetalum chinense var. rubrum (LC). The study revealed that light stress had a greater impact on rare species with relative abundances below 0.01% than on high-abundance species, regardless of the vegetation restoration pattern. Additionally, PV shadowing increased SBCs’ biomass by 20–30% but had varying negative effects on the numbers of Operational Taxonomic Unit (OTU), Shannon diversity, abundance-based coverage estimator (ACE), and Chao1 richness index. Co-occurrence and correlation network analysis revealed that symbiotic relationships dominated the key SBCs in the LC sample plots, with Chloroflexi and Actinobacteriota being the most ecologically important. In contrast, competitive relationships were significantly increased in the EP sample plots, with Actinobacteriota having the most ecological importance. In the EP sample plot, SBCs were found to be more tightly linked and had more stable ecological networks. This suggests that EP is more conducive to the stability and health of underground ecosystems in vulnerable areas when compared with LC. These findings offer new insights into the effects of small-scale light stress on subsurface microorganisms under different vegetation restoration patterns. Moreover, they may provide a reference for optimizing ecological restoration patterns in fragile areas

Data from: Recharge and groundwater use in the North China Plain for six irrigated crops for an eleven year period

These data include measured precipitation, measured pan evaporation, planting and harvest dates and measured soil moisture contents of 0-180 cm soil profile at approximately 10-day intervals, annual groundwater table data from 2003 to 2013 by China Agricultural University in cooperation with Luancheng Agro-Ecosystem Experimental Station of Chinese Academy of Sciences.(Related journal paper prepared in cooperation with Cornell University, BEE Soil and Water Lab. Paper abstract follows.) Water tables are dropping by approximately one meter annually throughout the North China Plain mainly due to water withdrawals for irrigating winter wheat year after year. In order to examine whether the drawdown can be reduced we calculate the net water use for an 11 year field experiments from 2003 to 2013 where six irrigated crops (winter wheat, summer maize, cotton, peanuts, sweet potato, ryegrass) were grown in different crop rotations in the North China Plain. As part of this experiment moisture contents were measured each at 20 cm intervals in the top 1.8 m. Recharge and net water use were calculated based on these moisture measurement. Results showed that winter wheat and ryegrass had the least recharge with an average of 27mm/year and 39 mm/year, respectively; cotton had the most recharge with an average of 211 mm/year) followed by peanuts with 118 mm/year, sweet potato with 76 mm/year, and summer maize with 44 mm/year. Recharge depended on the amount of irrigation water pumped from the aquifer and therefore a poor indicators of future groundwater decline. Instead net water use (recharge minus irrigation) was found to be good indicator for the decline of the water table. The smallest amount of net (ground water) used was cotton with an average of 14 mm/year, followed by peanut with 32 mm/year, summer maize with 71 mm/year, sweet potato with 74 mm/year. Winter wheat and ryegrass had the greatest net water use with the average of 198 mm/year and 111 mm/year, respectively. Our calculations showed that any single crop would use less water than the prevalent winter maize summer wheat rotation. This growing one crop instead of two will reduce the decline of groundwater and in some rain rich years increase the ground water level, but will result in less income for the farmers.China Agricultural University Funding:the National Key Technology R&D Program of the People's Republic of China (2011BAD16B15 and 2012BAD14B03), the China Scholarship Council for Xiaolin Yang (Grant No. 201306350107) and the Chinese Universities Scientific Fund (2013YJ001

Fast and abundant in vitro spontaneous haustorium formation in root hemiparasitic plant Pedicularis kansuensis Maxim. (Orobanchaceae)

Haustorium formation is the characteristic feature of all parasitic plants and a vital process for successful parasitism. Previous investigations on haustorium initiation and development are constricted to induced processes by host-derived signals or synthetic analogs. Spontaneous haustorium formation in the absence of host signals, a process representing an early stage in the evolution of parasitic plants, remains largely unexplored. Lack of fast and frequent formation of spontaneous haustoria greatly hinders full understanding of haustorium formation in root hemiparasites. In this study, seedlings of Pedicularis kansuensis Maxim., a facultative root hemiparasitic species in Orobanchaceae observed to produce many spontaneous haustoria, were grown in autoclaved water agar in the absence of any known haustorium-inducing stimulants. We aimed to test the temporal and developmental pattern of spontaneous haustorium formation. Also, effects of sucrose supply and root contact on spontaneous haustorium formation were tested. Spontaneous haustoria were observed starting from six days after germination, much earlier than previously reported root hemiparasites. A majority of the spontaneous haustoria formed on lateral roots. Percentage of seedlings with spontaneous haustoria was 28.8% when grown on water agar plates, with a mean of four haustoria per seedling two weeks after germination. Haustorium formation by seedlings grown in water agar amended with 2% sucrose was more than twice of those without sucrose amendment. Singly grown seedlings were able to develop spontaneous haustoria at similar levels as those grown with another conspecific seedling. In view of the fast and abundant formation of spontaneous haustoria, P. kansuensis may be developed as an excellent experimental system in future investigations for unraveling endogenous regulation of haustorium initiation and development in root hemiparasitic plants. Keywords: Spontaneous haustoria, Root hemiparasitic plants, Orobanchaceae, Pedicularis, Sucrose amendmen

Results and Analysis of BDS Precise Orbit Determination with the Enhancement of Fengyun-3C

Global navigation satellite system occultation sounder (GNOS) Fengyun-3C was launched successfully on September 23, 2013, which carried GPS/BDS receiver for the first time. This provides the convenience to study the enhancement results of low earth orbiter satellite (LEO) to BDS precise orbit determination (POD). First the data characteristics and code observation noise of GNOS are analyzed. Then the enhancement experiments in the case of global and regional ground observation stations layout are processed with four POD schemes: BDS single system, GPS/BDS double system, BDS single system with GNOS observations, GPS/BDS double system with GNOS observations. The precision of BDS orbits and clock are compared via overlapping arcs. Results show that in the case of global station layout the along directional precision of GEO satellite has the biggest improvement, with the improvement percentage 60%. Then the precision of cross direction and the along direction of remaining satellites shows the second biggest improvement. The orbit precision of only BDS POD in part of arcs some satellite even suffers a slight decline. The root mean square (RMS) of overlapping clock difference of visible arcs in GPS/BDS POD experiments is improved 0.1 ns level. As to the experiments of regional station layout with 7 ground observation stations, the orbit and clock overlapping precision and orbit predicting precision are analyzed. Results show that the predicting precision of BDS GEO satellites in the along direction is improved 85%. The remaining also has a substantial improvement, with the average percentage 21.7%. RMS of overlapping clock difference of visible arcs is improved 0.5 ns level

Exploring and applying the substrate promiscuity of a C-glycosyltransferase in the chemo-enzymatic synthesis of bioactive C-glycosides

C-glycosides are of pharmaceutical interest due to their stability against in vivo hydrolysis, however their enzymatic synthesis faces challenges. Here, the authors report a C-glycosyltransferase from Aloe barbadensis catalysing the C-glycosylation of drug-like acceptors to generate bioactive C-glycosides

Satellite precise orbit determination with ionospheric-free strategy using triple-frequency observations

As the development of global navigation satellite system (GNSS), GNSS satellites transmitting multi-frequency signals has become a prevailing trend. However, recently the international GNSS service (IGS) analysis centers still use dual-frequency (DF) observations to derive the orbits, clocks and other products. The additional observations from the third frequency are not considered. We use two DF ionospheric-free (IF) combinations as the observation model, the improvements from the third frequency on orbits, clocks and station positions are assessed. In the carrier phase observation model, the satellite-dependent time-invariant and time-variant components are introduced. The two DF IF observation equations are re-parameterized to make the clock parameter aligned to the IGS clock products, and then the full-rank TF observation model is derived. Based on the strategy of building up extra wide lane, wide lane and narrow lane double-differenced ambiguities, the TF ambiguity resolution (AR) method is deduced. First taking 12 GPS Block IIF satellites as example, three precise orbit determination (POD) schemes, the L1/L2 DF IF POD (denoting as S1), the L1/L5 DF IF POD (denoting as S2), the L1/L2 and L1/L5 TF IF POD (denoting as S3), are processed in two station layouts. Results show that the S3 scheme in two station layouts can obtain the optimal precision. The orbit improvements of S3 with respect to S1 in cases of even and uneven distribution are within 10% and about 10%, respectively. The improvement of clocks RMS is slight, while STD is improved by 6.4% and 10.0%. The improved percentages of S3 vs. S2 are about less one times than that of S3 vs. S1, with the improved percentage of about 5%. Then the BDS-only POD test is processed and the orbits are validated by satellite laser ranging residuals. Results show that comparing with B1/B3 POD, the orbit and clock accuracy of TF POD can be improved. However, the improvement of TF POD comparing to B1/B2 POD is slight or even worse. The possible reason is the inaccuracy antenna phase values

Application of bone alkaline phosphatase and 25-oxhydryl-vitamin D in diagnosis and prediction of osteoporotic vertebral compression fractures

Abstract Background Osteoporosis is a bone metabolic disease that usually causes fracture. The improvement of the clinical diagnostic efficiency of osteoporosis is of great significance for the prevention of fracture. The predictive and diagnostic values of bone alkaline phosphatase (B-ALP) and 25-oxhydryl-vitamin D (25-OH-VD) for osteoporotic vertebral compression fractures (OVCFs) were evaluated. Methods 110 OVCFs patients undergoing percutaneous vertebroplasty were included as subjects and their spinal computed tomography (CT) images were collected. After that, deep convolutional neural network model was employed for intelligent fracture recognition. Next, the patients were randomly enrolled into Ctrl group (65 cases receiving postoperative routine treatment) and VD2 group (65 cases injected with vitamin D2 into muscle after the surgery). In addition, 100 healthy people who participated in physical examination were included in Normal group. The differences in Oswestry dysfunction indexes (ODI), imaging parameters, B-ALP and 25-OH-VD expressions, and quality of life (QOL) scores of patients among the three groups were compared. The values of B-ALP and 25-OH-VD in predicting and diagnosing OVCFs and their correlation with bone density were analyzed. Results It was demonstrated that computer intelligent medical image technique was more efficient in fracture CT recognition than artificial recognition. In contrast to those among patients in Normal group, B-ALP rose while 25-OH-VD declined among patients in Ctrl and VD2 groups (P < 0.05). Versus those among patients in Ctrl group, ODI, Cobb angle, and B-ALP reduced, while bone density, the height ratio of the injured vertebrae, 25-OH-VD, and QOL score increased among patients in VD2 group after the treatment (P < 0.05). The critical values, accuracy, and areas under the curve (AUC) of the diagnosis of OVCFs by B-ALP and 25-OH-VD amounted to 87.8 μg/L versus 30.3 nmol/L, 86.7% versus 83.3%, and 0.86 versus 0.82, respectively. B-ALP was apparently negatively correlated with bone density (r =  − 0.602, P < 0.05), while 25-OH-VD was remarkably positively correlated with bone density (r = 0.576, P < 0.05). Conclusion To sum up, deep learning-based computer CT image intelligent detection technique could improve the diagnostic efficacy of fracture. B-ALP rose while 25-OH-VD declined among patients with OVCFs and OVCFs could be predicted and diagnosed based on B-ALP and 25-OH-VD. Postoperative intramuscular injection of VD2 could effectively improve the therapeutic effect on patients with OVCFs and QOL

GPS/BDS/Galileo precise orbit determination using triple-frequency uncombined observation model

The navigation satellite of the four global navigation satellite system (GNSS) transmitting multi-frequency signals becomes a prevailing trend. In this contribution, a triple-frequency (TF) uncombined (UC) precise orbit determination (POD) method based on IGS clock datum is developed and its ambiguity resolution strategy is proposed. The hardware delay of carrier phase is divided by time-invariant and variant components. Then the UC observation model is given by re-parameterizing the unknown parameters. The step-by-step ambiguity fixing method, i.e. the extra-wide-lane, wide-lane and narrow-lane ambiguities fixed in sequence, is deduced by using double-differenced ambiguities in a network. With the GPS ⅡF, BDS-2 and Galileo being able to transmit triple-frequency signals, the four POD tests are conducted: ionospheric-free (IF) POD of frequency 1/2, IF POD of frequency 1/3, UC POD of frequency 1/2, UC POD of TF signals. The three metrics of external orbit product, day boundary discontinuities and satellite laser ranging are used to validate the POD product accuracy. Results show that a subtle improvement are received with the addition of the third frequency observations. However, the improvement of GPS TF POD results with respect to L1/L2 POD is about 10%, which may be the signal power of L5 is stronger than that of L2