The protein kinase A/protein kinase G/protein kinase C-family (AGC kinase family) of eukaryotes is involved in regulating numerous biological processes. The 3-phosphoinositide- dependent protein kinase 1 (PDK1), is a conserved serine/threonine kinase in eukaryotes. To understand the roles of PDK1 homologous genes in cell death and immunity in tetraploid Nicotiana tabacum, the previuosly generated transgenic CRISPR/Cas9 lines, in which 5-7 alleles of the 4 homologous PDK1 genes (NtPDK1a/1b/1c/1d homologs) simultaneously knocked out, were used in this study. Our results showed that the hypersensitive response (HR) triggered by transient overexpression of active Pto (Pto^Y207D) or soybean GmMEKK1 was significantly delayed, whereas the resistance to Pseudomonas syrangae pv. tomato DC3000 (Pst DC3000) and tobacco mosaic virus (TMV) was significantly elevated in these partial knockout lines. The elevated resistance to Pst DC3000 and TMV was correlated with the elevated activation of NtMPK6, NtMPK3, and NtMPK4. Taken together, our results indicated that NtPDK1s play a positive role in cell death but a positive role in disease resistance, likely through negative regulation of the MAPK signaling cascade.
Nicotiana/virology* ; Disease Resistance/genetics* ; Plant Diseases/immunology* ; Plants, Genetically Modified/genetics* ; Gene Knockout Techniques ; Plant Proteins/genetics* ; CRISPR-Cas Systems ; Protein Serine-Threonine Kinases/genetics* ; 3-Phosphoinositide-Dependent Protein Kinases/genetics* ; Pyruvate Dehydrogenase Acetyl-Transferring Kinase ; Tobacco Mosaic Virus/pathogenicity*

Microalgae possess high photosynthetic efficiency, robust adaptability, and substantial biomass, serving as excellent biological resources for large-scale cultivation. Malic enzyme (ME), a ubiquitous metabolic enzyme in living organisms, catalyzes the decarboxylation of malate to produce pyruvate, CO₂, and NAD(P)H, playing a role in multiple metabolic pathways including energy metabolism, photosynthesis, respiration, and biosynthesis. In this study, we identified the Scenedesmus quadricauda malic enzyme gene (SqME) and its biological functions, aiming to provide excellent target genes for the genetic improvement of higher plants. Based on the RNA-seq data from S. quadricauda under the biofilm cultivation mode with high CO₂ and light energy transfer efficiency and small water use, a highly expressed gene (SqME) functionally annotated as ME was cloned. The physicochemical properties of the SqME-encoded protein were systematically analyzed by bioinformatics tools. The subcellular localization of SqME was determined via transient transformation in Nicotiana benthamiana leaves. The biological functions of SqME were identified via genetic transformation in Nicotiana tabacum, and the potential of SqME in the genetic improvement of higher plants was evaluated. The ORF of SqME was 1 770 bp, encoding 590 amino acid residues, and the encoded protein was located in chloroplasts. SqME was a NADP-ME, with the typical structural characteristics of ME. The ME activity in the transgenic N. tabacum plant was 1.8 folds of that in the wild-type control. Heterologous expression of SqME increased the content of chlorophyll a, chlorophyll b, and total chlorophyll by 20.9%, 26.9%, and 25.2%, respectively, compared with the control. The transgenic tobacco leaves showed an increase of 54.0% in the fluorescence parameter NPQ and a decrease of 30.1% in Fo compared with the control. Moreover, the biomass, total lipids, and soluble sugars in the transgenic tobacco leaves enhanced by 20.5%, 25.7%, and 9.5%, respectively. On the contrary, the starch and protein content in the transgenic tobacco leaves decreased by 22.4% and 12.2%, respectively. Collectively, the SqME-encoded protein exhibited a strong enzymatic activity. Heterologous expressing of SqME could significantly enhance photosynthetic protection, photosynthesis, and biomass accumulation in the host. Additionally, SqME can facilitate carbon metabolism remodeling in the host, driving more carbon flux towards lipid synthesis. Therefore, SqME can be applied in the genetic improvement of higher plants for enhancing photosynthetic carbon fixation and lipid accumulation. These findings provide scientific references for mining of functional genes from S. quadricauda and application of these genes in the genetic engineering of higher plants.
Nicotiana/genetics* ; Photosynthesis/physiology* ; Malate Dehydrogenase/biosynthesis* ; Plant Leaves/genetics* ; Scenedesmus/enzymology* ; Carbon Cycle/genetics* ; Lipid Metabolism/genetics* ; Plants, Genetically Modified/metabolism*

Geminiviruses cause substantial crop yield losses worldwide. The replication initiator protein (Rep) encoded by geminiviruses is indispensable for geminiviral replication. The Rep protein encoded by beet severe curly top virus (BSCTV, genus Curtovirus, family Geminiviridae) induces VARIANT IN METHYLATION 5 (VIM5) expression in Arabidopsis leaves upon BSCTV infection. VIM5 functions as a ubiquitination-related E3 ligase to promote the proteasomal degradation of methyltransferases, resulting in reduction of methylation levels in the BSCTV C2-3 promoter. However, the specific domains of Rep responsible for VIM5 induction remain poorly characterized. Although Rep proteins from several geminiviruses act as viral suppressors of RNA silencing (VSRs), whether BSCTV Rep also possesses VSR activity remains to be illustrated. In this study, we employed a transient expression system in the 16c-GFP transgenic and the wild-type Nicotiana benthamiana plants to analyze the VSR and the VIM5-inducing activities of different truncated Rep proteins haboring distinct domains. We found that the N-terminal domain (amino acids 1-180) of Rep suppressed GFP silencing in 16c-GFP transgenic N. benthamiana leaves. The minimal N-terminal fragment (amino acids 1-104) induced VIM5 expression upon co-infiltration, while C-terminal truncations lacked VIM5-inducing activity. Our results indicate that the N-terminal domain of Rep encoded by BSCTV mediates the suppression of RNA silencing and induces VIM5 expression. Thus, our findings contribute to a better understanding of interactions between geminiviral Rep and plant hosts.
Geminiviridae/genetics* ; Nicotiana/metabolism* ; Arabidopsis/metabolism* ; RNA Interference ; Viral Proteins/metabolism* ; Arabidopsis Proteins/metabolism* ; Plants, Genetically Modified/metabolism* ; Protein Domains ; Plant Diseases/virology* ; Methyltransferases/metabolism* ; Ubiquitin-Protein Ligases/metabolism* ; DNA Helicases/genetics*

TCP family as plant specific transcription factor, plays an important role in different aspects of plant development. In order to screen TCP family members in tobacco, the homologous sequences of tobacco and Arabidopsis TCP family were identified by genome-wide homologous alignment. The physicochemical properties, phylogenetic relationships and cis-acting elements were analyzed by bioinformatics. The homologous genes of AtTCP3/AtTCP4 were screened, and RT-qPCR was used to detect the changes of gene expression upon 20% PEG6000 treatment. The results show that tobacco contains 63 TCP family members. Their amino acid sequence length ranged from 89 aa to 596 aa, and their protein hydropathicity grand average of hydropathicity (GRAVY) ranged from -1.147 to 0.125. The isoelectric point (pI) ranges from 4.42 to 9.94, the number of introns is 0 to 3, and the subcellular location is all located in the nucleus. The results of conserved domain and phylogenetic relationship analysis showed that the tobacco TCP family can be divided into PCF, CIN and CYC/TB1 subfamilies, and each subfamily has a stable sequence. The results of cis-acting elements in gene promoter region showed that TCP family genes contain low docile acting elements (LTR) and a variety of stress and metabolic regulation related elements (MYB, MYC). Analysis of gene expression patterns showed that AtTCP3/AtTCP4 homologous genes (NtTCP6, NtTCP28, NtTCP30, NtTCP33, NtTCP42, NtTCP57, NtTCP63) accounted for 20% PEG6000 treatment significantly up-regulated/down-regulated expression, and NtTCP30 and NtTCP57 genes were selected as candidate genes in response to drought. The results of this study analyzed the TCP family in the tobacco genome and provided candidate genes for the study of drought-resistance gene function and variety breeding in tobacco.
Nicotiana/genetics* ; Phylogeny ; Plant Breeding ; Amino Acid Sequence ; Arabidopsis ; Polyethylene Glycols

Plant bioreactor is a new production platform for expression of recombinant protein, which is one of the cores of molecular farming. In this study, the anti DYKDDDDK (FLAG) antibody was recombinantly expressed in tobacco (Nicotiana benthamiana) and purified. FLAG antibody with high affinity was obtained after immunizing mice for several times and its sequence was determined. Based on this, virus vectors expressing heavy chain (HC) and light chain (LC) inoculated into Nicotiana benthamiana leaves by using Agrobacterium-mediated delivery. Accumulation of the HC and LC was analyzed by SDS/PAGE followed by Western blotting probed with specific antibodies from 2 to 9 days postinfiltration (dpi). Accumulation of the FLAG antibody displayed at 3 dpi, and reached a maximum at 5 dpi. It was estimated that 66 mg of antibody per kilogram of fresh leaves could be obtained. After separation and purification, the antibody was concentrated to 1 mg/mL. The 1:10 000 diluted antibody can probe with 1 ng/mL FLAG fused antigen well, indicating the high affinity of the FLAG antibody produced in plants. In conclusion, the plant bioreactor is able to produce high affinity FLAG antibodies, with the characteristics of simplicity, low cost and highly added value, which contains enormous potential for the rapid and abundant biosynthesis of antibodies.
Animals ; Mice ; Antibodies ; Nicotiana/genetics* ; Agrobacterium/genetics* ; Bioreactors ; Blotting, Western

Production of reactive oxygen species (ROS) is a conserved immune response primarily mediated by NADPH oxidases (NOXs), also known in plants as respiratory burst oxidase homologs (RBOHs). Most microbe-associated molecular patterns (MAMPs) trigger a very fast and transient ROS burst in plants. However, recently, we found that lipopolysaccharides (LPS), a typical bacterial MAMP, triggered a biphasic ROS burst. In this study, we isolated mutants defective in LPS-triggered biphasic ROS burst (delt) in Arabidopsis, and cloned the DELT1 gene that was shown to encode RBOHD. In the delt1-2 allele, the antepenultimate residue, glutamic acid (E919), at the C-terminus of RBOHD was mutated to lysine (K). E919 is a highly conserved residue in NADPH oxidases, and a mutation of the corresponding residue E568 in human NOX2 has been reported to be one of the causes of chronic granulomatous disease. Consistently, we found that residue E919 was indispensable for RBOHD function in the MAMP-induced ROS burst and stomatal closure. It has been suggested that the mutation of this residue in other NADPH oxidases impairs the protein's stability and complex assembly. However, we found that the E919K mutation did not affect RBOHD protein abundance or the ability of protein association, suggesting that the residue E919 in RBOHD might have a regulatory mechanism different from that of other NOXs. Taken together, our results confirm that the antepenultimate residue E is critical for NADPH oxidases and provide a new insight into the regulatory mechanisms of RBOHD.
Agrobacterium tumefaciens/metabolism* ; Alleles ; Arabidopsis/metabolism* ; Arabidopsis Proteins/genetics* ; Gene Expression Regulation, Plant ; Genetic Techniques ; Humans ; Lipopolysaccharides/metabolism* ; Luminescence ; Mutation ; NADPH Oxidase 2/chemistry* ; NADPH Oxidases/genetics* ; Plant Stomata/metabolism* ; Protein Domains ; Reactive Oxygen Species/metabolism* ; Nicotiana/metabolism*