Dynamic changes in transcripts during regeneration of the secondary vascular system in Populus tomentosa Carr. revealed by cDNA microarrays

<p>Abstract</p> <p>Background</p> <p>Wood is the end product of secondary vascular system development, which begins from the cambium. The wood formation process includes four major stages: cell expansion, secondary wall biosynthesis, lignification, and programmed cell death. Transcriptional profiling is a rapid way to screen for genes involved in these stages and their transitions, providing the basis for understanding the molecular mechanisms that control this process.</p> <p>Results</p> <p>In this study, cDNA microarrays were prepared from a subtracted cDNA library (cambium zone <it>versus </it>leaf) of Chinese white poplar (<it>Populus tomentosa </it>Carr.) and employed to analyze the transcriptional profiles during the regeneration of the secondary vascular system, a platform established in our previous study. Two hundred and seven genes showed transcript-level differences at the different regeneration stages. Dramatic transcriptional changes were observed at cambium initiation, cambium formation and differentiation, and xylem development, suggesting that these up- or downregulated genes play important roles in these stage transitions. Transcription factors such as AUX/IAA and PINHEAD, which were previously shown to be involved in meristem and vascular tissue differentiation, were strongly transcribed at the stages when cambial cells were initiated and underwent differentiation, whereas genes encoding MYB proteins and several small heat shock proteins were strongly transcribed at the stage when xylem development begins.</p> <p>Conclusion</p> <p>Employing this method, we observed dynamic changes in gene transcript levels at the key stages, including cambium initiation, cambium formation and differentiation, and xylem development, suggesting that these up- or downregulated genes are strongly involved in these stage transitions. Further studies of these genes could help elucidate their roles in wood formation.</p

Physiological and transcriptome analyses to infer regulatory networks in flowering transition of Rosa rugosa

Rosa rugosa is a famous Chinese traditional flowering species with high economic value. Flowering transition is an important process in plant growth and development. Although characterization of the flowering transition process has made great progress in some plants such as model plants, the process in R. rugosa has not been rigorously characterized to establish a mechanism. In this study, the changes of buds during flowering transition in R. rugosa ‘Duoji Huangmei’ were analyzed through transcriptomic sequencing combined with morphological and physiological index determinations. Results showed that with the morphology changes of buds, both sugar and starch content showed a similar up-down pattern while phytohormones content displayed various trends, which implied that sugar, starch and phytohormones might play diverse roles during flowering transition in R. rugosa. Moreover, a total of 4363 differentially expressed genes (DEGs) were identified at three developmental stages. Among them, 74 DEGs were involved in metabolism, transport, and signal transduction of sugar, starch, and phytohormones, as well as photoperiod and vernalization response. We proposed that these DEGs were not regulated independently but interacted with each other to construct a gene-gene network to regulate flowering transition of R. rugosa, and the regulatory network from vegetative growth stage (S1) to flowering transition stage (S2) was more complicated. These results further enriched the study of flowering transition in Rosa and lay an important foundation for breeding new varieties with desired floral traits

Adding power of artificial intelligence to situational awareness of large interconnections dominated by inverter‐based resources

Large-scale power systems exhibit more complex dynamics due to the increasing integration of inverter-based resources (IBRs). Therefore, there is an urgent need to enhance the situational awareness capability for better monitoring and control of power grids dominated by IBRs. As a pioneering Wide-Area Measurement System, FNET/GridEye has developed and implemented various advanced applications based on the collected synchrophasor measurements to enhance the situational awareness capability of large-scale power grids. This study provides an overview of the latest progress of FNET/GridEye. The sensors, communication, and data servers are upgraded to handle ultra-high density synchrophasor and point-on-wave data to monitor system dynamics with more details. More importantly, several artificial intelligence (AI)-based advanced applications are introduced, including AI-based inertia estimation, AI-based disturbance size and location estimation, AI-based system stability assessment, and AI-based data authentication

Draft genome sequence of the mulberry tree Morus notabilis

Human utilization of the mulberry–silkworm interaction started at least 5,000 years ago and greatly influenced world history through the Silk Road. Complementing the silkworm genome sequence, here we describe the genome of a mulberry species Morus notabilis. In the 330-Mb genome assembly, we identify 128 Mb of repetitive sequences and 29,338 genes, 60.8% of which are supported by transcriptome sequencing. Mulberry gene sequences appear to evolve ~3 times faster than other Rosales, perhaps facilitating the species’ spread worldwide. The mulberry tree is among a few eudicots but several Rosales that have not preserved genome duplications in more than 100 million years; however, a neopolyploid series found in the mulberry tree and several others suggest that new duplications may confer benefits. Five predicted mulberry miRNAs are found in the haemolymph and silk glands of the silkworm, suggesting interactions at molecular levels in the plant–herbivore relationship. The identification and analyses of mulberry genes involved in diversifying selection, resistance and protease inhibitor expressed in the laticifers will accelerate the improvement of mulberry plants

Synthesis of thioarsenate compounds and their occurrence characteristics in groundwater: A case study of Datong Basin

As an important occurrence form of arsenic in sulfur-rich groundwater, thioarsenate plays a very important role in its migration and transformation. However, the standard synthesis method of thioarsenate is complex and the occurrence characteristics and influencing factors in low temperature groundwater are rarely reported. In this paper, firstly, the synthesis method of thioarsenate reference material was improved, the standard reference material of thioarsenate was synthesized by hydrothermal method, and the analytical method of thioarsenate based on HPLC-ICPMS was established. The detection limit of this method was 0.01 μg/L. The effects of different preservation conditions on the stability of thioarsenate compounds were discussed. It was found that quick freezing of dry ice at -20℃ was the best way to keep the stability of thioarsenate samples in groundwater. The above method was used to analyze thioarsenate in groundwater in Datong Basin. The results showed that thioarsenate was detected in 40% of the water samples, and the highest concentrate was 209.90 μg/L. The weak alkaline reduction condition is beneficial to the occurrence of thioarsenate, and the sulfide concentration plays an important role in controlling the formation of thioarsenate. The in-depth study of thioarsenate in groundwater is helpful to reveal the law of migration and transformation of arsenic in sulfur-rich groundwater and is of great significance to enrich the genetic theory of high-arsenic groundwater

Solution Procedure for Transport Modeling in Effluent Recharge Based on Operator-Splitting Techniques

The coupling of groundwater movement and reactive transport during groundwater recharge with wastewater leads to a complicated mathematical model, involving terms to describe convection-dispersion, adsorption/desorption and/or biodegradation, and so forth. It has been found very difficult to solve such a coupled model either analytically or numerically. The present study adopts operator-splitting techniques to decompose the coupled model into two submodels with different intrinsic characteristics. By applying an upwind finite difference scheme to the finite volume integral of the convection flux term, an implicit solution procedure is derived to solve the convection-dominant equation. The dispersion term is discretized in a standard central-difference scheme while the dispersion-dominant equation is solved using either the preconditioned Jacobi conjugate gradient (PJCG) method or Thomas method based on local-one-dimensional scheme. The solution method proposed in this study is applied to the demonstration project of groundwater recharge with secondary effluent at Gaobeidian sewage treatment plant (STP) successfully

Chaotification for a Class of Delay Difference Equations Based on Snap-Back Repellers

We study the chaotification problem for a class of delay difference equations by using the snap-back repeller theory and the feedback control approach. We first study the stability and expansion of fixed points and establish a criterion of chaos. Then, based on this criterion of chaos and the feedback control approach, we establish a chaotification scheme such that the controlled system is chaotic in the sense of both Devaney and Li-Yorke when the parameters of this system satisfy some mild conditions. For illustrating the theoretical result, we give some computer simulations

Formation Of Bimetallic Dumbbell Shaped Particles With A Hollow Junction During Galvanic Replacement Reaction

The galvanic replacement reaction (GRR) has been shown to be an effective method to fine tune the structure of monometallic nanoparticles by controlling the precursor concentration and surface ligands. However, the structural evolution of nanoparticles is not well understood in multimetallic systems, where along with oxidation, dealloying and diffusion occur simultaneously. Here, we demonstrate that by controlling the rate of GRR in AuCu alloy nanorods, they can be transformed into either AuCu hollow rods or AuCu@Au core-shell spheroids. Interestingly, the transformation of rods into spheroids involved a critical intermediate state with a hollow junction and dumbbell shape. The formation of a hollow junction region was attributed to preferential diffusion of Cu atoms to the tips caused by the polycrystallinity and high curvature of the tips of the initial template. This structural transformation was also monitored in situ by single particle scattering spectroscopy. The coupling between the two ends of the dumbbell-shaped intermediate connected with a hollow metallic junction gives rise to additional plasmonic features compared with regular rods. Electrodynamic simulations showed that varying the dimensions of the hollow part by even one nanometer altered the plasmon resonance wavelength and lineshape drastically. This study shows that single particle plasmon resonance can be used as an exquisite tool to probe the internal structure of the nanoscale junctions

Identification of microRNAs involved in regeneration of the secondary vascular system in populus tomentosa carr

© 2016 Tang, Wei, Zhao, Wang, Zheng and Lu. Wood formation is a complex developmental process primarily controlled by a regulatory transcription network. MicroRNAs (miRNAs) can modulate the expression of target genes involved in plant growth and development by inducing mRNA degradation and translational repression. In this study, we used a model of secondary vascular system regeneration established in Populus tomentosa to harvest differentiating xylem tissues over time for high-throughput sequencing of small RNAs. Analysis of the sequencing data identified 209 known and 187 novel miRNAs during this regeneration process. Degradome sequencing analysis was then performed, revealing 157 and 75 genes targeted by 21 known and 30 novel miRNA families, respectively. Gene ontology enrichment of these target genes revealed that the targets of 15 miRNAs were enriched in the auxin signaling pathway, cell differentiation, meristem development, and pattern specification process. The major biological events during regeneration of the secondary vascular system included the sequential stages of vascular cambium initiation, formation, and differentiation stages in sequence. This study provides the basis for further analysis of these miRNAs to gain greater insight into their regulatory roles in wood development in trees