SR45a plays a key role in enhancing cotton resistance to Verticillium dahliae by alternative splicing of immunity genes.

Alternative splicing (AS) of pre-mRNAs increases the diversity of transcriptome and proteome and plays fundamental roles in plant development and stress responses. However, the prevalent changes in AS events and the regulating mechanisms of plants in response to pathogens remain largely unknown. Here, we show that AS changes are an important mechanism conferring cotton immunity to Verticillium dahliae (Vd). GauSR45a, encoding a serine/arginine-rich RNA binding protein, was upregulated expression and underwent AS in response to Vd infection in Gossypium australe, a wild diploid cotton species highly resistant to Vd. Silencing GauSR45a substantially reduced the splicing ratio of Vd-induced immune-associated genes, including GauBAK1 (BRI1-associated kinase 1) and GauCERK1 (chitin elicitor receptor kinase 1). GauSR45a binds to the GAAGA motif that is commonly found in the pre-mRNA of genes essential for PTI, ETI, and defense. The binding between GauSR45a and the GAAGA motif in the pre-mRNA of BAK1 was enhanced by two splicing factors of GauU2AF35B and GauU1-70 K, thereby facilitating exon splicing; silencing either AtU2AF35B or AtU1-70 K decreased the resistance to Vd in transgenic GauSR45a Arabidopsis. Overexpressing the short splicing variant of BAK1GauBAK1.1 resulted in enhanced Verticillium wilt resistance rather than the long one GauBAK1.2. Vd-induced far more AS events were in G. barbadense (resistant tetraploid cotton) than those in G. hirsutum (susceptible tetraploid cotton) during Vd infection, indicating resistance divergence in immune responses at a genome-wide scale. We provided evidence showing a fundamental mechanism by which GauSR45a enhances cotton resistance to Vd through global regulation of AS of immunity genes.

General Regulatory Factor7 regulates innate immune signalling to enhance Verticillium wilt resistance in cotton.

Sessile growing plants are always vulnerable to microbial pathogen attacks throughout their lives. To fend off pathogen invasion, plants have evolved a sophisticated innate immune system that consists of cell surface receptors and intracellular receptors. Somatic embryogenesis receptor kinases (SERKs) belong to a small group of leucine-rich repeat receptor-like kinases (LRR-RLKs) that function as co-receptors regulating diverse physiological processes. GENRAL REGULATORY FACTOR (GRF) proteins play an important role in physiological signalling transduction. However, the function of GRF proteins in plant innate immune signalling remains elusive. Here, we identified a GRF gene, GauGRF7, that is expressed both constitutively and in response to fungal pathogen infection. Intriguingly, silencing of GRF7 compromised plant innate immunity, resulting in susceptibility to Verticillium dahliae infection. Both transgenic GauGRF7 cotton and transgenic GauGRF7 Arabidopsis lines enhanced the innate immune response to V. dahliae infection, leading to high expression of two helper NLRs (hNLR) genes (ADR1 and NRG1) and pathogenesis-related genes, and increased ROS production and salicylic acid level. Moreover, GauGRF7 interacted with GhSERK1, which positively regulated GRF7-mediated innate immune response in cotton and Arabidopsis. Our findings revealed the molecular mechanism of the GRF protein in plant immune signaling and offer potential opportunities for improving plant resistance to V. dahliae infection.

RVE2, a new regulatory factor in jasmonic acid pathway, orchestrates resistance to Verticillium wilt.

Verticillium dahliae, one of the most destructive fungal pathogens of several crops, challenges the sustainability of cotton productivity worldwide because very few widely-cultivated Upland cotton varieties are resistant to Verticillium wilt (VW). Here, we report that REVEILLE2 (RVE2), the Myb-like transcription factor, confers the novel function in resistance to VW by regulating the jasmonic acid (JA) pathway in cotton. RVE2 expression was essentially required for the activation of JA-mediated disease-resistance response. RVE2 physically interacted with TPL/TPRs and disturbed JAZ proteins to recruit TPL and TPR1 in NINJA-dependent manner, which regulated JA response by relieving inhibited-MYC2 activity. The MYC2 then bound to RVE2 promoter for the activation of its transcription, forming feedback loop. Interestingly, a unique truncated RVE2 widely existing in D-subgenome (GhRVE2D) of natural Upland cotton represses the ability of the MYC2 to activate GhRVE2A promoter but not GausRVE2 or GbRVE2. The result could partially explain why Gossypium barbadense popularly shows higher resistance than Gossypium hirsutum. Furthermore, disturbing the JA-signalling pathway resulted into the loss of RVE2-mediated disease-resistance in various plants (Arabidopsis, tobacco and cotton). RVE2 overexpression significantly enhanced the resistance to VW. Collectively, we conclude that RVE2, a new regulatory factor, plays a pivotal role in fine-tuning JA-signalling, which would improve our understanding the mechanisms underlying the resistance to VW.

Perovskite-Nanocrystal-Doped Cellulose Nanocrystal Ligands for Electrospun Nanofibers with Excellent Stability.

Because of their exceptional physical and thermal properties, cellulose nanocrystals (CNCs) are a highly promising bio-based material for reinforcing fillers. Studies have revealed that some functional groups from CNCs can be used as a capping ligand to coordinate with metal nanoparticles or semiconductor quantum dots during the fabrication of novel complex materials. Therefore, through CNCs ligand encapsulation and electrospinning, perovskite-NC-embedded nanofibers with exceptional optical and thermal stability are demonstrated. The results indicate that, after continuous irradiation or heat cycling, the relative photoluminescence (PL) emission intensity of the CNCs-capped perovskite-NC-embedded nanofibers is maintained at ≈90%. However, the relative PL emission intensity of both ligand-free and long-alkyl-ligand-doped perovskite-NC-embedded nanofibers decrease to almost 0%. These results are attributable to the formation of specific clusters of perovskite NCs along with the CNCs structure and thermal property improvement of polymers. CNCs-doped luminous complex materials offer a promising avenue for stability-demanding optoelectronic devices and other novel optical applications.

ATP-citrate lyase B (ACLB) negatively affects cell death and resistance to Verticillium wilt.

BACKGROUND: ATP-citrate lyase (ACL) plays a pivotal role in histone acetylation and aerobic glycolysis. In plant, ACL is a heteromeric enzyme composed of ACLA (45 kD) and ACLB (65 kD). So far, the function of ACL genes in cotton still remains unknown. RESULTS: Here, we identified three ACLA homologous sequences and two ACLB homologous in each genome/sub-genome of cotton species. Silencing ACLB in cotton led to cell death at newly-grown leaves and stem apexes. Simultaneously, in ACLB-silenced plants, transcription factors related to senescence including SGR, WRKY23 and Osl57 were observed to be activated. Further investigation showed that excessive H2O2 was accumulated, salicylic acid-dependent defense response and pathogenesis-related gene expressions were evidently enhanced in ACLB-silenced plants, implying that knockdown of ACLB genes leads to hypersensitive response-like cell death in cotton seedlings. However, as noted, serious cell death happened in newly-grown leaves and stem apexes in ACLB-silenced plants, which led to the failure of subsequent fungal pathogenicity assays. To confirm the role of ACLB gene in regulating plant immune response, the dicotyledonous model plant Arabidopsis was selected for functional verification of ACLB gene. Our results indicate the resistance to Verticillium dahliae infection in the Arabidopsis mutant aclb-2 were enhanced without causing strong cell death. Ectopic expression of GausACLB-2 in Arabidopsis weakened its resistance to V. dahliae either in Col-0 or in aclb-2 background, in which the expression level of ACLB is negatively correlated with the resistance to V. dahliae. CONCLUSIONS: These results indicate that ACLB has a new function in negatively affecting the induction of plant defense response and cell death in cotton, which provides theoretical guidance for developing cotton varieties with resistance against Verticillium wilt.

Cu-Doped Boron Nitride Nanosheets for Solid-Phase Extraction and Determination of Rhodamine B in Foods Matrix.

Cu-doped boron nitride nanosheets (Cu-BNNS) were first reported as promising adsorbents for the solid-phase extraction and determination of rhodamine B (RhB) dye in a food matrix. Different characterizations, including XRD, FTIR, XPS, SEM, and TEM, were performed to confirm the formation of the adsorbent. Then, the adsorption performance of Cu-BNNS was investigated by adsorption kinetics, isotherms, and thermodynamics. Multiple extraction parameters were optimized by single-factor experiments. Under optimized conditions, the recoveries in the food matrix were in the range of 89.8-95.4%, with the spiked levels of 100 ng/mL and 500 ng/mL, respectively. This novel system was expected to have great potential to detect RhB in a wide variety of real samples.

Genome-Wide Identification and Expression Profile Analysis of the PHT1 Gene Family in Gossypium hirsutum and Its Two Close Relatives of Subgenome Donor Species.

Phosphate transporter (PHT) is responsible for plant phosphorus (P) absorption and transport. PHT1 is a component of the high-affinity phosphate transporter system and plays pivotal roles in P absorption under P starvation conditions. However, in cotton, the number and identity of PHT1 genes that are crucial for P absorption from soil remain unclear. Here, genome-wide identification detected twelve PHT1 genes in Gossypium hirsutum and seven and eight PHT1 genes in two close relatives of the G. hirsutum genome-G. arboreum and G. raimondii, respectively. In addition, under low-phosphate treatment, the expressions of GaPHT1;3, GaPHT1;4, and GaPHT1;5 in roots were upregulated after 3 h of induction, and GhPHT1;3-At, GhPHT1;4-At, GhPHT1;5-At, GhPHT1;3-Dt, GhPHT1;4-Dt, and GhPHT1;5-Dt in the roots began to respond after 1 h of induction. Homologous pairs-GaPHT1;4 and GhPHT1;4-At; GaPHT1;5 and GhPHT1;5-At; GrPHT1;4 and GhPHT1;4-Dt, with GhPHT1;5-Dt and GhPHT1;5-At being syntenic-were all highly expressed in the roots under normal conditions. Among the genes highly expressed in the roots, GhPHT1;4-At, GhPHT1;5-At, GhPHT1;4-Dt and GhPHT1;5-Dt were continuously upregulated by P starvation. Therefore, it is concluded that these four genes might be key genes for P uptake in cotton roots. The results of this study provide insights into the mechanisms of P absorption and transport in cotton.

Reconstruction of the full-length transcriptome atlas using PacBio Iso-Seq provides insight into the alternative splicing in Gossypium australe.

BACKGROUND: Gossypium australe F. Mueller (2n = 2x = 26, G2 genome) possesses valuable characteristics. For example, the delayed gland morphogenesis trait causes cottonseed protein and oil to be edible while retaining resistance to biotic stress. However, the lack of gene sequences and their alternative splicing (AS) in G. australe remain unclear, hindering to explore species-specific biological morphogenesis. RESULTS: Here, we report the first sequencing of the full-length transcriptome of the Australian wild cotton species, G. australe, using Pacific Biosciences single-molecule long-read isoform sequencing (Iso-Seq) from the pooled cDNA of ten tissues to identify transcript loci and splice isoforms. We reconstructed the G. australe full-length transcriptome and identified 25,246 genes, 86 pre-miRNAs and 1468 lncRNAs. Most genes (12,832, 50.83%) exhibited two or more isoforms, suggesting a high degree of transcriptome complexity in G. australe. A total of 31,448 AS events in five major types were found among the 9944 gene loci. Among these five major types, intron retention was the most frequent, accounting for 68.85% of AS events. 29,718 polyadenylation sites were detected from 14,536 genes, 7900 of which have alternative polyadenylation sites (APA). In addition, based on our AS events annotations, RNA-Seq short reads from germinating seeds showed that differential expression of these events occurred during seed germination. Ten AS events that were randomly selected were further confirmed by RT-PCR amplification in leaf and germinating seeds. CONCLUSIONS: The reconstructed gene sequences and their AS in G. australe would provide information for exploring beneficial characteristics in G. australe.

[Study on the skin-core evolvement of carbon fibers as a function of heat treatment temperature by Raman spectroscopy].

The skin-core evolvement of the carbon fibers was studied as a function of heat-treatment temperature though the analysis of Raman spectroscopy of the carbon fibers surface and core. It was found that the change of the Raman spectra of the carbon fibers core was similar to that on the surface with the increase in heat-treatment temperature. At 1600 degrees C, the Rs and Rc values were almost equal, indicating that the degrees of the graphitization of the carbon fibers surface and core were almost uniform. The Rs and Rc values decreased dramatically with the increase in heat-treatment temperature, and Rs decreased more. At 2800 degrees C, the Rs value came to 0.429, lowered 77.2%, while the Rc value then came to 1.101, lowered 38.7% only. It implied that the graphitization degree of the carbon fibers was enhanced with increasing the heat treatment temperature, and that of carbon fibers surface was enhanced more. The graphite characters of the carbon of the carbon fibers surface were different from that of the carbon fibers core. The former is close to soft carbon, which is easy to graphitize, while the latter is close to hard carbon, which is difficult to graphitize, and it may be resin carbon Skin-core structure gene Rsc (= Rs/Rc) which denoted the skin-core degree of the carbon fibers was first brought forward and adopted. The Rsc value is between 0 and 1. When the Rsc value is equal to 1, the carbon fibers are homogenous. When the Rsc value is close to zero, there are serious skin-core structures in the carbon fibers. The Rsc value reduced linearly with the increase in heat-treatment temperature, indicating that the homogeneous degrees of the carbon fibers decreased and the skin-core degrees of the carbon fibers increased. The crystallite size of the carbon fibers surface and core increased gradually with the increase in heat-treatment temperature, but the surface's increased more quickly, indicating that the carbon of the carbon fibers surface was easier to graphitize than the carbon fibers core. Serious skin-core structure was one of the reasons that caused the reducing of the carbon fibers' tensile strength.