Elucidating the Role of Lipid Interactions in Stabilizing the Membrane Protein KcsA.

The significant effects of lipid binding on the functionality of potassium channel KcsA have been validated by brilliant studies. However, the specific interactions between lipids and KcsA, such as binding parameters for each binding event, have not been fully elucidated. In this study, we employed native mass spectrometry to investigate the binding of lipids to KcsA and their effects on the channel. The tetrameric structure of KcsA remains intact even in the absence of lipid binding. However, the subunit architecture of the E71A mutant, which is constantly open at low pH, relies on tightly associated copurified lipids. Furthermore, we observed that lipids exhibit weak binding to KcsA at high pH when the channel is at a closed/inactivation state in the absence of permeant cation K+. This feeble interaction potentially facilitates the association of K+ ions, leading to the transition of the channel to a resting closed/open state. Interestingly, both anionic and zwitterionic lipids strongly bind to KcsA at low pH when the channel is in an open/inactivation state. We also investigated the binding patterns of KcsA with natural lipids derived from E. coli and S. lividans. Interestingly, lipids from E. coli exhibited much stronger binding affinity compared to the lipids from S. lividans. Among the natural lipids from S. lividans, free fatty acids and triacylglycerols demonstrated the tightest binding to KcsA, whereas no detectable binding events were observed with natural PA lipids. These findings suggest that the lipid association pattern in S. lividans, the natural host for KcsA, warrants further investigation. In conclusion, our study sheds light on the role of lipids in stabilizing KcsA and highlights the importance of specific lipid-protein interactions in modulating its conformational states.

The plant peptide hormone phytosulfokine promotes somatic embryogenesis by maintaining redox homeostasis in Cunninghamia lanceolata.

Somatic embryogenesis (SE) is widely used for studying the mechanisms of embryo development. However, little is known about the underlying mechanisms, especially in woody plants. Previous studies have established an SE system for Chinese fir (Cunninghamia lanceolata), but this system is genotype-dependent, which limits its application in practice. Here, we found that phytosulfokine (PSK), a plant peptide hormone, can not only increase SE efficiency, but also establish SE in recalcitrant genotypes of C. lanceolata. Proembryogenic mass (PEM) browning and determination of hydrogen peroxide (H2 O2 ) content by 2',7'-dichlorofluorescein staining indicated that a reactive oxygen species (ROS) burst occurred rapidly after PEMs were transferred to SE induction medium. Transcriptome analysis and quantitative reverse transcriptase-PCR validation showed that PSK treatment helped to maintain ROS homeostasis by decreasing the activity of peroxidases in early SE induction. This PSK-regulated redox microenvironment might be helpful to induce expression of SE-related genes like WOX2 in early SE induction. Further analyses suggested that PSK promotes SE induction in C. lanceolata partially through decreasing H2 O2 levels, which is necessary but not sufficient for SE induction in recalcitrant genotypes of C. lanceolata. Furthermore, heterologous overexpression of ClPSK in Arabidopsis led to enhanced SE induction and resistance to H2 O2 stress. Taken together, our study reveals a biological function for the plant peptide hormone PSK, extends our knowledge about SE in woody trees, and provides a valuable tool for establishing an efficient and genotype-independent SE system in C. lanceolata and other coniferous trees.

Genome-wide characterization of post-transcriptional processes related to wood formation in Dalbergia odorifera.

BACKGROUND: Alternative polyadenylation (APA), alternative splicing (AS), and long non-coding RNAs (lncRNAs) play regulatory roles in post-transcriptional processes in plants. However, little is known about their involvement in xylem development in Dalbergia odorifera, a valuable rosewood species with medicinal and commercial significance. We addressed this by conducting Isoform Sequencing (Iso-Seq) using PacBio's SMRT technology and combined it with RNA-seq analysis (RNA sequencing on Illumina platform) after collecting xylem samples from the transition zone and the sapwood of D. odorifera. RESULTS: We identified 14,938 full-length transcripts, including 9,830 novel isoforms, which has updated the D. odorifera genome annotation. Our analysis has revealed that 4,164 genes undergo APA, whereas 3,084 genes encounter AS. We have also annotated 118 lncRNAs. Furthermore, RNA-seq analysis identified 170 differential alternative splicing (DAS) events, 344 genes with differential APA site usage (DE-APA), and 6 differentially expressed lncRNAs in the transition zone when compared to the sapwood. AS, APA, and lncRNAs are differentially regulated during xylem development. Differentially expressed APA genes were enriched for terpenoid and flavonoid metabolism, indicating their role in the heartwood formation. Additionally, DE-APA genes were associated with cell wall biosynthesis and terpenoid metabolism, implying an APA's role in wood formation. A DAS gene (involved in chalcone accumulation) with a significantly greater inclusion of the last exon in the transition zone than in the sapwood was identified. We also found that differentially expressed lncRNAs targeted the genes related to terpene synthesis. CONCLUSIONS: This study enhances our understanding of the molecular regulatory mechanisms underlying wood formation in D. odorifera, and provides valuable genetic resources and insights for its molecular-assisted breeding.

CRISPR/Cas genome editing in plants: mechanisms, applications, and overcoming bottlenecks.

The CRISPR/Cas systems have emerged as transformative tools for precisely manipulating plant genomes and enhancement. It has provided unparalleled applications from modifying the plant genomes to resistant enhancement. This review manuscript summarises the mechanism, application, and current challenges in the CRISPR/Cas genome editing technology. It addresses the molecular mechanisms of different Cas genes, elucidating their applications in various plants through crop improvement, disease resistance, and trait improvement. The advent of the CRISPR/Cas systems has enabled researchers to precisely modify plant genomes through gene knockouts, knock-ins, and gene expression modulation. Despite these successes, the CRISPR/Cas technology faces challenges, including off-target effects, Cas toxicity, and efficiency. In this manuscript, we also discuss these challenges and outline ongoing strategies employed to overcome these challenges, including the development of novel CRISPR/Cas variants with improved specificity and specific delivery methods for different plant species. The manuscript will conclude by addressing the future perspectives of the CRISPR/Cas technology in plants. Although this review manuscript is not conclusive, it aims to provide immense insights into the current state and future potential of CRISPR/Cas in sustainable and secure plant production.

Identification and characterization of functionally relevant SSR markers in natural Dalbergia odorifera populations.

BACKGROUND: Dalbergia odorifera is a rare and precious rosewood specie, which is valued for its amber tones, abstract figural patterns, and impermeability to water and insects. However, the information on genetic diversity and marker-assisted selection breeding of D. odorifera is still limited. Simple sequence repeat (SSR) markers are an ideal tool for genetic diversity analysis and marker-assisted molecular breeding for complex traits. RESULTS: Here, we have developed SSR markers within candidate genes and used them to explore the genetic diversity among D. odorifera germplasm resources. A total of 635 SSR loci were identified. The proportions of mono-, di- and tri-nucleotide repeat motifs were 52.28%, 22.99% and 21.42%, respectively. From these, a total of 114 SSR primers were synthesized, of which 24 SSR markers displayed polymorphism (polymorphic information content (PIC) > 0.25). Subsequently, these polymorphic markers were used for the genetic diversity analysis of 106 D. odorifera individuals from 11 natural populations. According to the genetic diversity analysis of D. odorifera natural populations, the average observed heterozygosity (Ho) was 0.500, the average expected heterozygosity (He) was 0.524, and the average Shannon's information index (I) was 0.946. These indicated that the natural populations had moderate genetic diversity. AMOVA analysis showed that 5% of the total variation was within the individuals of a population, whereas 95% of the variation was among the individuals of the populations, indicating a high degree of genetic variation between populations. On the basis of their genetic structures, these populations could be divided into four groups. CONCLUSIONS: Our study provides important experimental resources for genetic studies and assists in the program of molecular breeding of D. odorifera wood formation.

Genomic survey and expression analysis of LcARFs reveal multiple functions to somatic embryogenesis in Liriodendron.

BACKGROUND: Auxin response factors (ARFs) are critical transcription factors that mediate the auxin signaling pathway and are essential for regulating plant growth. However, there is a lack of understanding regarding the ARF gene family in Liriodendron chinense, a vital species in landscaping and economics. Thus, further research is needed to explore the roles of ARFs in L. chinense and their potential applications in plant development. RESULT: In this study, we have identified 20 LcARF genes that belong to three subfamilies in the genome of L. chinense. The analysis of their conserved domains, gene structure, and phylogeny suggests that LcARFs may be evolutionarily conserved and functionally similar to other plant ARFs. The expression of LcARFs varies in different tissues. Additionally, they are also involved in different developmental stages of somatic embryogenesis. Overexpression of LcARF1, LcARF2a, and LcARF5 led to increased activity within callus. Additionally, our promoter-GFP fusion study indicated that LcARF1 may play a role in embryogenesis. Overall, this study provides insights into the functions of LcARFs in plant development and embryogenesis, which could facilitate the improvement of somatic embryogenesis in L. chinense. CONCLUSION: The research findings presented in this study shed light on the regulatory roles of LcARFs in somatic embryogenesis in L. chinense and may aid in accelerating the breeding process of this tree species. By identifying the specific LcARFs involved in different stages of somatic embryogenesis, this study provides a basis for developing targeted breeding strategies aimed at optimizing somatic embryogenesis in L. chinense, which holds great potential for improving the growth and productivity of this economically important species.

Bilateral Production Shield Enabling Highly Efficient Perovskite Photovoltaics.

Enhancing the intrinsic stability of perovskite and through encapsulation to isolate water, oxygen, and UV-induced decomposition are currently common and most effective strategies in perovskite solar cells. Here, the atomic layer deposition process is employed to deposit a nanoscale (≈100 nm), uniform, and dense Al2O3 film on the front side of perovskite devices, effectively isolating them from the erosion caused by water and oxygen in the humid air. Simultaneously, nanoscale (≈100 nm) TiO2 films are also deposited on the glass surface to efficiently filter out the ultraviolet (UV) light in the light source, which induces degradation in perovskite. Ultimately, throughthe collaborative effects of both aspects, the stability of the devices is significantly improved under conditions of humid air and illumination. As a result, after storing the devices in ambient air for 1000 h, the efficiency only declines to 95%, and even after 662 h of UV exposure, the efficiency remains at 88%, far surpassing the performance of comparison devices. These results strongly indicate that the adopted Al2O3 and TiO2 thin films play a significant role in enhancing the stability of perovskite solar cells, demonstrating substantial potential for widespread industrial applications.

The critical roles of propanethiol oxidoreductase and sulfide-quinone oxidoreductase in the propanethiol catabolism pathway in Pseudomonas putida S-1.

Propanethiol (PT) is a hazardous pollutant that poses risks to both the environment and human well-being. Pseudomonas putida S-1 has been identified as a microorganism capable of utilizing PT as its sole carbon source. However, the metabolic pathway responsible for PT degradation in P. putida S-1 has remained poorly understood, impeding its optimization and practical application. In this study, we investigated the catabolic network involved in PT desulfurization with P. putida S-1 and identified key gene modules crucial to this process. Notably, propanethiol oxidoreductase (PTO) catalyzes the initial degradation of PT, a pivotal step for P. putida S-1's survival on PT. PTO facilitates the oxidation of PT, resulting H2S, H2O2, and propionaldehyde (PA). Catalase-peroxidase catalyzes the conversion of H2O2 to oxygen and water, while PA undergoes gradual conversion to Succinyl-CoA, which is subsequently utilized in the tricarboxylic acid cycle. H2S is digested in a comprehensive desulfurization network where sulfide-quinone oxidoreductase (SQOR) predominantly converts it to sulfane sulfur. The transcriptome analysis suggests that sulfur can be finally converted to sulfite or sulfate and exported out of the cell. The PT degradation capacity of P. putida S-1 was enhanced by increasing the transcription level of PTO and SQOR genes in vivo.IMPORTANCEThis work investigated the PT catabolism pathway in Pseudomonas putida S-1, a microorganism capable of utilizing PT as the sole carbon source. Critical genes that control the initiation of PT degradation were identified and characterized, such as pto and sqor. By increasing the transcription level of pto and sqor genes in vivo, we have successfully enhanced the PT degradation efficiency and growth rate of P. putida S-1. This work does not only reveal a unique PT degradation pathway but also highlights the potential of enhancing the microbial desulfurization process in the bioremediation of thiol-contaminated environment.

Tailoring whispering-gallery fields in optical black hole cavities.

The ability to confine light has great significance in both fundamental science and practical applications. Optical black hole (OBH) cavities show intriguing zero radiation loss and strong field confinement. In this work, we systematically explore the whispering gallery mode (WGM) in a group of generalized OBH cavities, featuring bound states and strong field confinement. The field confinement in generalized OBH cavities is revealed to be enhanced with the increase of index-modulation factors, resulting from the increase of a potential barrier. Furthermore, we reveal the anomalous external resonant modes, exhibiting fascinating field enhancement in the low-index region far beyond the cavity boundary. These anomalous WGMs are attributed to the potential bending effect and above-barrier resonance. Our work may shed light on tailoring WGM fields in gradient-index cavities and find potential applications in light coupling and optical sensing.

Distinct Assembly Processes Structure Planktonic Bacterial Communities Among Near- and Offshore Ecosystems in the Yangtze River Estuary.

The estuarine system functions as natural filters due to its ability to facilitate material transformation, planktonic bacteria play a crucial role in the cycling of complex nutrients and pollutants within estuaries, and understanding the community composition and assembly therein is crucial for comprehending bacterial ecology within estuaries. Despite extensive investigations into the composition and community assembly of two bacterial fractions (free-living, FLB; particle-attached, PAB), the process by which bacterioplankton communities in these two habitats assemble in the nearshore and offshore zones of estuarine ecosystems remains poorly understood. In this study, we conducted sampling in the Yangtze River Estuary (YRE) to investigate potential variations in the composition and community assembly of FLB and PAB in nearshore and offshore regions. We collected 90 samples of surface, middle, and bottom water from 16 sampling stations and performed 16S rRNA gene amplicon analysis along with environmental factor measurements. The results unveiled that the nearshore communities demonstrated significantly greater species richness and Chao1 indices compared to the offshore communities. In contrast, the nearshore communities had lower values of Shannon and Simpson indices. When compared to the FLB, the PAB exhibit a higher level of biodiversity and abundance. However, no distinct alpha and beta diversity differences were observed between the bottom, middle, and surface water layers. The community assembly analysis indicated that nearshore communities are predominantly shaped by deterministic processes, particularly due to heterogeneous selection of PAB; In contrast, offshore communities are governed more by stochastic processes, largely due to homogenizing dispersal of FLB. Consequently, the findings of this study demonstrate that nearshore and PAB communities exhibit higher levels of species diversity, while stochastic and deterministic processes exert distinct influences on communities among near- and offshore regions. This study further sheds new light on our understanding of the mechanisms governing bacterial communities in estuarine ecosystems.

Sox9 is required in regeneration of pancreatic ß cells following injury.

The reduction of insulin secretion due to pancreatic ß cell injury caused by autoimmune reaction is the pathological basis of Type 1 diabetes mellitus (T1DM). Therefore, seeking new molecular targets for alleviating pancreatic ß cell injury will provide experimental basis for the prevention and treatment of T1DM. SRY-box 9 (Sox9) is not only an important molecule regulating the development of various organs, but also its high expression can aggravate the pathological process of various diseases. In addition, Sox9+ cells are also pancreatic progenitor cells, participating in pancreatic repair reaction induced by injury. In our study, elevated blood glucose and lack of pancreatic ß cells almost returned to normal over time after streptozotocin (STZ)-induced pancreatic ß cell damage, implying that pancreatic ß cells were regenerated after STZ-induced injury. In particular, the expression of Sox9 was significantly elevated during pancreatic ß cell regeneration. On this basis, we conducted in vitro experiments to verify whether overexpression of Sox9 could inhibit the damage of pancreatic ß cells by inflammatory factors. Our results showed that overexpression of Sox9 alleviated the damage of pancreatic ß cells by inflammatory factors and improved the inhibitory effect of inflammatory factors on insulin secretion of pancreatic ß cells. Unsurprising, blood glucose levels, insulin content and pancreatic ß cell number failed to return to near-normal levels timely after pancreatic ß cells specific knockout Sox9 mice were treated with STZ, further confirming the importance of Sox9 in facilitating pancreatic ß cell repair or regeneration. Our study indicate that enhanced Sox9 activity might protect pancreatic ß cells from autoimmune induced damage and thus improve the pathological process of T1DM.

Local adjuncts to minimally invasive endoscopic interventions for benign laryngotracheal stenosis: a meta-analysis.

BACKGROUND: Benign laryngotracheal stenosis is widely managed with minimally invasive endoscopic interventions, such as laser incision or excision scar, and dilation. However, various endoscopic treatments are significantly associated with a high recurrence rate. Local auxiliary measures, including inhalation of steroids, injection of steroids, and local topical application of mitomycin C, have been studied in order to increase the success rate. PURPOSE: To compare the efficacy of endoscopic treatments with and without local adjuncts in patients with benign laryngotracheal stenosis, and analyze their clinical outcomes, recurrence, and complications. METHODS: In the meta-analysis, databases including PubMed, EMBASE, OVID, and Web of Science were searched for papers comparing the outcomes of adjunct therapy with non-adjunct therapy in patients with laryngotracheal stenosis. The duplicate publications, reviews, comments or letters, conference abstracts, and case reports were excluded. The random effect model was used for assessing the pooled risk estimates. RESULTS: Eight studies (1204 cases) referring to two prospective randomized controlled studies, two prospective cohort studies, and four retrospective cohort studies were ultimately included in the meta-analysis. Three delivery modes of adjuncts were identified, including intralesion steroid injection (n = 2), inhaled steroid (n = 2), and topical application of mitomycin C (n = 4). The decreased risk estimates of recurrence rate were detected in patients receiving endoscopic treatments with steroid injection or inhaled steroid, compared with endoscopic interventions alone (P < 0.05). Additionally, patients undergoing adjunct therapies had lower risk estimates of recurrence, compared to those receiving endoscopic procedures alone (P < 0.05), based on the subgroup of prospective cohort studies, subglottis, Mayer-Cotton scale of I-II degree, and stenosis length of < 3 cm. The high heterogeneity of the pooling risk estimates perhaps was due to factors of auxiliary drug, clinical characteristics of patients, and methodology. No discernible difference in the incidence of complication was identified. CONCLUSIONS: Local application of steroids to minimally invasive interventions appear to reduce the recurrence rate of laryngotracheal stenosis. Various adjuncts available, including steroids and mitomycin C, appear to be safe and associated with a low risk estimate of adjuncts-specific complication rate. High quality multi-center randomized controlled studies are needed, with sufficient periods for follow-up and subjective and objective outcome indicators, to properly evaluate the efficacy, safety, and cost-effectiveness of adjuvant drugs.

Soft Polymer Optical Fiber Sensors for Intelligent Recognition of Elastomer Deformations and Wearable Applications.

In recent years, soft robotic sensors have rapidly advanced to endow robots with the ability to interact with the external environment. Here, we propose a polymer optical fiber (POF) sensor with sensitive and stable detection performance for strain, bending, twisting, and pressing. Thus, we can map the real-time output light intensity of POF sensors to the spatial morphology of the elastomer. By leveraging the intrinsic correlations of neighboring sensors and machine learning algorithms, we realize the spatially resolved detection of the pressing and multi-dimensional deformation of elastomers. Specifically, the developed intelligent sensing system can effectively recognize the two-dimensional indentation position with a prediction accuracy as large as ~99.17%. The average prediction accuracy of combined strain and twist is ~98.4% using the random forest algorithm. In addition, we demonstrate an integrated intelligent glove for the recognition of hand gestures with a high recognition accuracy of 99.38%. Our work holds promise for applications in soft robots for interactive tasks in complex environments, providing robots with multidimensional proprioceptive perception. And it also can be applied in smart wearable sensing, human prosthetics, and human-machine interaction interfaces.

Evolution of the WRKY Family in Angiosperms and Functional Diversity under Environmental Stress.

The transcription factor is an essential factor for regulating the responses of plants to external stimuli. The WRKY protein is a superfamily of plant transcription factors involved in response to various stresses (e.g., cold, heat, salt, drought, ions, pathogens, and insects). During angiosperm evolution, the number and function of WRKY transcription factors constantly change. After suffering from long-term environmental battering, plants of different evolutionary statuses ultimately retained different numbers of WRKY family members. The WRKY family of proteins is generally divided into three large categories of angiosperms, owing to their conserved domain and three-dimensional structures. The WRKY transcription factors mediate plant adaptation to various environments via participating in various biological pathways, such as ROS (reactive oxygen species) and hormone signaling pathways, further regulating plant enzyme systems, stomatal closure, and leaf shrinkage physiological responses. This article analyzed the evolution of the WRKY family in angiosperms and its functions in responding to various external environments, especially the function and evolution in Magnoliaceae plants. It helps to gain a deeper understanding of the evolution and functional diversity of the WRKY family and provides theoretical and experimental references for studying the molecular mechanisms of environmental stress.

Genome-Wide Analysis of the Liriodendron chinense Hsf Gene Family under Abiotic Stress and Characterization of the LcHsfA2a Gene.

Heat shock factors (Hsfs) play a crucial role in plant defense processes. However, the distribution and functional characteristics of Hsf genes in the relict plant Liriodendron chinense are still unclear. In this study, a total of 19 LcHsfs were identified and divided into three separate subgroups, comprising 10 LcHsfA, 7 LcHsfB, and 2 LcHsfC genes, respectively, based on their phylogenetic tree and the presence/absence of conserved protein domains. Whole-genome duplication and segmental duplication led to an expansion of the LhHsf gene family. The promoters of LcHsf genes are enriched for different types of cis-acting elements, including hormone responsive and abiotic-stress-responsive elements. The expression of LcHsfA3, LcHsfA4b, LcHsfA5, LcHsfB1b, and LcHsfB2b increased significantly as a result of both cold and drought treatments. LcHsfA2a, LcHsfA2b, and LcHsfA7 act as important genes whose expression levels correlate strongly with the expression of the LcHsp70, LcHsp110, and LcAPX genes under heat stress. In addition, we found that transiently transformed 35S:LcHsfA2a seedlings showed significantly lower levels of hydrogen peroxide (H2O2) after heat stress and showed a stronger thermotolerance. This study sheds light on the possible functions of LcHsf genes under abiotic stress and identifies potentially useful genes to target for molecular breeding, in order to develop more stress-resistant varieties.

H2O2 Significantly Affects Larix kaempferi × Larix olgensis Somatic Embryogenesis.

Larch is widely distributed throughout the world and is an important species for timber supply and the extraction of industrial raw materials. In recent years, the hybrid breeding of Larix kaempferi and Larix olgensis has shown obvious heterosis in quick-growth, stress resistance and wood properties. However, its growth and development cycle is too long to meet general production needs. In order to shorten the breeding cycle, we have for the first time successfully established and optimized a somatic embryogenesis system for Larix kaempferi × Larix olgensis. We found that the highest rate of embryonal-suspensor mass (ESM) induction was observed when late cotyledonary embryos were used as explants. The induced ESMs were subjected to stable proliferation, after which abscisic acid (ABA) and polyethylene glycol (PEG) were added to successfully induce somatic embryos. Treatment with PEG and ABA was of great importance to somatic embryo formation and complemented each other's effect. ABA assisted embryo growth, whereas PEG facilitated the formation of proembryo-like structures. On top of this, we studied in more detail the relationship between redox homeostasis and the efficiency of somatic embryogenesis (frequency of ESM induction). During subculture, we observed the gradual formation of three distinct types of ESM. The Type I ESM is readily able to form somatic embryos. In contrast to type I, the type III ESM suffers from severe browning, contains a higher level of hydrogen peroxide (H2O2) and demonstrates a decreased ability to form somatic embryos. External treatment with H2O2 decreased the somatic embryogenesis efficiency of Type I and type III ESMs, or the higher the exogenous H2O2 content, the lower the resulting somatic embryogenesis efficiency. We found that treatment with the H2O2 scavenger DMTU (dimethylthiourea) could significantly increase the somatic embryogenesis efficiency of the type III ESM, as a result of a decline in endogenous H2O2 content. Overall, these findings have contributed to setting up a successful somatic embryogenesis system for larch production.

Overexpression of Liriodendron Hybrid LhGLK1 in Arabidopsis Leads to Excessive Chlorophyll Synthesis and Improved Growth.

Chloroplasts is the site for photosynthesis, which is the main primary source of energy for plants. Golden2-like (GLK) is a key transcription factor that regulates chloroplast development and chlorophyll synthesis. However, most studies on GLK genes are performed in crops and model plants with less attention to woody plants. In this study, we identified the LhGLK1 and LhGLK2 genes in the woody plant Liriodendron hybrid, and they are specifically expressed in green tissues. We showed that overexpression of the LhGLK1 gene improves rosette leaf chlorophyll content and induces ectopic chlorophyll biogenesis in primary root and petal vascular tissue in Arabidopsis. Although these exhibit a late-flowering phenotype, transgenic lines accumulate more biomass in vegetative growth with improved photochemical quenching (qP) and efficiency of photosystem II. Taken together, we verified a conserved and ancient mechanism for regulating chloroplast biogenesis in Liriodendron hybrid and evaluated its effect on photosynthesis and rosette biomass accumulation in the model plant Arabidopsis.

Genome-wide identification of the NAC gene family and its functional analysis in Liriodendron.

As one of the largest plant specific transcription factor families, NAC family members play an important role in plant growth, development and stress resistance. To investigate the function of NAC transcription factors during abiotic stress, as well as during somatic embryogenesis, we identified and characterized the NAC gene family in Liriodendron chinense. We found that most LcNAC members contain more than three exons, with a relatively conserved gene and motif structure, especially at the N-terminus. Interspecies collinearity analysis revealed a closer relationship between the L. chinense NACs and the P. trichocarpa NACs. We analyzed the expression of LcNAC in different tissues and under three abiotic stresses. We found that 12 genes were highly expressed during the ES3 and ES4 stages of somatic embryos, suggesting that they are involved in the development of somatic embryos. 6 LcNAC genes are highly expressed in flower organs. The expression pattern analysis of LcNACs based on transcriptome data and RT-qPCR obtained from L. chinense leaves indicated differential expression responses to drought, cold, and heat stress. Genes in the NAM subfamily expressed differently during abiotic stress, and LcNAC6/18/41/65 might be the key genes in response to abiotic stress. LcNAC6/18/41/65 were cloned and transiently transformed into Liriodendron protoplasts, where LcNAC18/65 was localized in cytoplasm and nucleus, and LcNAC6/41 was localized only in nucleus. Overall, our findings suggest a role of the NAC gene family during environmental stresses in L. chinense. This research provides a basis for further study of NAC genes in Liriodendron chinense.

Phytosulfokine contributes to suspension culture of Cunninghamia lanceolata through its impact on redox homeostasis.

BACKGROUND: Suspension culture is widely used in the establishment of efficient plant regeneration systems, as well as in the mass production of plant secondary metabolites. However, the establishment of a suspension culture system of Cunninghamia lanceolata is genotype-dependent given that proembryogenic masses (PEMs) are prone to browning during this process in recalcitrant genotypes. Previously, we reported that the plant peptide hormone phytosulfokine (PSK) can tremendously decrease the hydrogen peroxide (H2O2) level and help to initiate somatic embryogenesis (SE) in recalcitrant C. lanceolata genotypes. However, to date, no studies have revealed whether or how PSK may contribute to the establishment of a suspension culture system in these recalcitrant genotypes. RESULTS: Here, we demonstrated that exogenous application of PSK effectively inhibited PEM browning during suspension culture in a recalcitrant genotype of C. lanceolata. Comparative time-series transcriptome profiling showed that redox homeostasis underwent drastic fluctuations when PEMs were cultured in liquid medium, while additional PSK treatment helped to maintain a relatively stable redox homeostasis. Interestingly, PSK seemed to have a dual effect on peroxidases (PRXs), with PSK simultaneously transcriptionally repressing ROS-producing PRXs and activating ROS-scavenging PRXs. Furthermore, determination of H2O2 and MDA content, as well as cell viability, showed that exogenous PSK treatment inhibited PEM browning and safeguarded PEM suspension culture by decreasing the H2O2 level and increasing PEM activity. CONCLUSIONS: Collectively, these findings provide a valuable tool for the future establishment of large-scale C. lanceolata PEM suspension culture without genotype limitations.

miR394 enhances WUSCHEL-induced somatic embryogenesis in Arabidopsis thaliana.

Many plant species can give rise to embryos from somatic cells after a simple hormone treatment, illustrating the remarkable developmental plasticity of differentiated plant cells. However, many species are recalcitrant to somatic embryo formation for unknown reasons, which poses a significant challenge to agriculture, where somatic embryogenesis is an important tool to propagate desired genotypes. The micro-RNA394 (miR394) promotes shoot meristem maintenance in Arabidopsis thaliana, but the underlying mechanisms have remained elusive. We analyzed whether miR394 affects indirect somatic embryogenesis and determined the transcriptome of embryogenic callus upon miR394-enhanced somatic embryogenesis. We show that ectopic miR394 expression enhances somatic embryogenesis in the recalcitrant Ler accession when co-expressed with the transcription factor WUSCHEL (WUS) and that miR394 acts in this process through silencing the target LEAF CURLING RESPONSIVENESS (LCR). Furthermore, we show that higher endogenous miR394 levels are required for the elevated embryogenic potential of the Columbia accession compared with Ler, providing a mechanistic explanation for this natural variation. Our transcriptional analysis provides a framework for miR394 function in regulating pluripotency by expanding WUS-mediated direct transcriptional repression.