Genome-wide identification of Shaker K+ channel family in Nicotiana tabacum and functional analysis of NtSKOR1B in response to salt stress.

Soil salinization poses a mounting global ecological and environmental threat. The identification of genes responsible for negative regulation of salt tolerance and their utilization in crop improvement through gene editing technologies emerges as a swift strategy for the effective utilization of saline-alkali lands. One efficient mechanism of plant salt tolerance is maintaining the proper intracellular K+/Na+ ratio. The Shaker K+ channels play a crucial role in potassium absorption, transport, and intracellular potassium homeostasis in plant cells. Here, the study presents the first genome-wide identification of Shaker K+ channels in Nicotiana tabacum L., along with a detailed bioinformatic analysis of the 20 identified members. Transcriptome analysis revealed a significant up-regulation of NtSKOR1B, an outwardly-rectifying member predominantly expressed in the root tissue of tobacco seedlings, in response to salt stress. This finding was then confirmed by GUS staining of ProNtSKOR1B::GUS transgenic lines and RT-qPCR analysis. Subsequently, NtSKOR1B knockout mutants (ntskor1) were then generated and subjected to salt conditions. It was found that ntskor1 mutants exhibit enhanced salt tolerance, characterized by increased biomass, higher K+ content and elevated K+/Na+ ratios in both leaf and root tissues, compared to wild-type plants. These results indicate that NtSKOR1B knockout inhibits K+ efflux in root and leaf tissues of tobacco seedlings under salt stress, thereby maintaining higher K+/Na+ ratios within the cells. Thus, our study identifies NtSKOR1B as a negative regulator of salt tolerance in tobacco seedlings.

Dysfunction of CD169+ macrophages and blockage of erythrocyte maturation as a mechanism of anemia in Plasmodium yoelii infection.

Plasmodium parasites cause malaria with disease outcomes ranging from mild illness to deadly complications such as severe malarial anemia (SMA), pulmonary edema, acute renal failure, and cerebral malaria. In young children, SMA often requires blood transfusion and is a major cause of hospitalization. Malaria parasite infection leads to the destruction of infected and noninfected erythrocytes as well as dyserythropoiesis; however, the mechanism of dyserythropoiesis accompanied by splenomegaly is not completely understood. Using Plasmodium yoelii yoelii 17XNL as a model, we show that both a defect in erythroblastic island (EBI) macrophages in supporting red blood cell (RBC) maturation and the destruction of reticulocytes/RBCs by the parasites contribute to SMA and splenomegaly. After malaria parasite infection, the destruction of both infected and noninfected RBCs stimulates extramedullary erythropoiesis in mice. The continuous decline of RBCs stimulates active erythropoiesis and drives the expansion of EBIs in the spleen, contributing to splenomegaly. Phagocytosis of malaria parasites by macrophages in the bone marrow and spleen may alter their functional properties and abilities to support erythropoiesis, including reduced expression of the adherence molecule CD169 and inability to support erythroblast differentiation, particularly RBC maturation in vitro and in vivo. Therefore, macrophage dysfunction is a key mechanism contributing to SMA. Mitigating and/or alleviating the inhibition of RBC maturation may provide a treatment strategy for SMA.

The CBL-Interacting Protein Kinase NtCIPK23 Positively Regulates Seed Germination and Early Seedling Development in Tobacco (Nicotiana tabacum L.).

CBL-interacting protein kinase (CIPK) family is a unique group of serine/threonine protein kinase family identified in plants. Among this family, AtCIPK23 and its homologs in some plants are taken as a notable group for their importance in ions transport and stress responses. However, there are limited reports on their roles in seedling growth and development, especially in Solanaceae plants. In this study, NtCIPK23, a homolog of AtCIPK23 was cloned from Nicotiana tabacum. Expression analysis showed that NtCIPK23 is mainly expressed in the radicle, hypocotyl, and cotyledons of young tobacco seedlings. The transcriptional level of NtCIPK23 changes rapidly and spatiotemporally during seed germination and early seedling growth. To study the biological function of NtCIPK23 at these stages, the overexpressing and CRISPR/Cas9-mediated knock-out (ntcipk23) tobacco lines were generated. Phenotype analysis indicated that knock-out of NtCIPK23 significantly delays seed germination and the appearance of green cotyledon of young tobacco seedling. Overexpression of NtCIPK23 promotes cotyledon expansion and hypocotyl elongation of young tobacco seedlings. The expression of NtCIPK23 in hypocotyl is strongly upregulated by darkness and inhibited under light, suggesting that a regulatory mechanism of light might underlie. Consistently, a more obvious difference in hypocotyl length among different tobacco materials was observed in the dark, compared to that under the light, indicating that the upregulation of NtCIPK23 contributes greatly to the hypocotyl elongation. Taken together, NtCIPK23 not only enhances tobacco seed germination, but also accelerate early seedling growth by promoting cotyledon greening rate, cotyledon expansion and hypocotyl elongation of young tobacco seedlings.

Expression analysis of taste receptor genes (T1R1, T1R3, and T2R4) in response to bacterial, viral and parasitic infection in rainbow trout, Oncorhynchus mykiss.

Emerging evidence suggests that bitter and sweet Taste receptors (TRs) in the airway are important sentinels of innate immunity. TRs are G protein-coupled receptors that trigger downstream signaling cascades in response to activation of specific ligands. Among them, the T1R family consists of three genes: T1R1, T1R2, and T1R3, which function as heterodimers for sweet tastants and umami tastants. While the other TRs family components T2Rs function as bitter tastants. To understand the relationship between TRs and mucosal immunity in teleost, here, we firstly identified and analyzed the molecular characteristics of three TRs (T1R1, T1R3, and T2R4) in rainbow trout (Oncorhynchus mykiss). Secondly, by quantitative real-time PCR (qPCR), we detected the mRNA expression levels of T1R1, T1R3 and T2R4 and found that the three genes could be tested in all detected tissues (pharynx, buccal cavity, tongue, nose, gill, eye, gut, fin, skin) and the expression levels of T1R3 and T2R4 were higher in buccal mucosa (BM) and pharyngeal mucosa (PM) compare to other tissues. It may suggest that T1R3 and T2R4 play important roles in BM and PM. Then, to analyses the changes of expression levels of the three genes in rainbow trout infected with pathogens, we established three infection models Flavobacterium columnare (F. cloumnare), infectious hematopoietic necrosis virus (IHNV) and Ichthyophthirius multifiliis (Ich). Subsequently, by qPCR, we detected the expression profiles of TRs in the gustatory tissues (BM, PM and skin) of rainbow trout after infection with F. cloumnare, IHNV, and Ich, respectively. We found that under three different infection models, the expression of the T1R1, T1R3 and T2R4 showed their own changes in mRNA levels. And the expression levels of the T1R1, T1R3 and T2R4 changed significantly at different time points in response to three infection models, respectively, suggesting that TRs may be associated with mucosal immunity.

Molecular characterization of a new recombinant brassica yellows virus infecting tobacco in China.

Brassica yellows virus (BrYV), prevalently distributed throughout mainland China and South Korea while triggering serious diseases in cruciferous crops, is proposed to be a new species in the genus Polerovirus within the family Luteoviridae. There are three distinct genotypes (BrYV-A, BrYV-B and BrYV-C) reported in cabbage and radish. Here, we describe a new BrYV isolate infecting tobacco plants in the field, which was named BrYV-NtabQJ. The complete genome sequence of BrYV-NtabQJ is 5741 nt in length, and 89% of the sequence shares higher sequence identities (about 90%) with different BrYV isolates. However, it possesses a quite divergent region within ORF5, which is more close to Beet western yellows virus (BWYV), Beet mild yellowing virus (BMYV) and Beet chlorosis virus (BChV). A significant recombination event was then detected among BrYV-NtabQJ, BrYV-B Beijng isolate (BrYV-BBJ) and BWYV Leonurus sibiricus isolate (BWYV-LS). It is proposed that BrYV-NtabQJ might be an interspecific recombinant between BrYV-BBJ and BWYV-LS, and the recombination might result in the successful aphid transmission of BrYV from cruciferous crops to tobacco. And it also poses new challenges for BrYV diagnosis and the vegetable production.