Drought is one of the most severe forms of abiotic stresses that threaten the survival of plants, including crops. In turn, plants dramatically change their physiology to increase drought tolerance, including reconfiguration of proteomes. Here, we studied drought-induced proteomic changes in leaves of cultivated tobacco (Nicotiana tabacum), a solanaceous plant, using the isobaric tags for relative and absolute quantitation (iTRAQ)-based protein labeling technology. Of identified 5570 proteins totally, drought treatment increased and decreased abundance of 260 and 206 proteins, respectively, compared with control condition. Most of these differentially regulated proteins are involved in photosynthesis, metabolism, and stress and defense. Although abscisic acid (ABA) levels greatly increased in drought-treated tobacco leaves, abundance of detected ABA biosynthetic enzymes showed no obvious changes. In contrast, heat shock proteins (HSPs), thioredoxins, ascorbate-, glutathione-, and hydrogen peroxide (H2O2)-related proteins were up- or down-regulated in drought-treated tobacco leaves, suggesting that chaperones and redox signaling are important for tobacco tolerance to drought, and it is likely that redox-induced posttranslational modifications play an important role in modulating protein activity. This study not only provides a comprehensive dataset on overall protein changes in drought-treated tobacco leaves, but also shed light on the mechanism by which solanaceous plants adapt to drought stress.

Abscisic acid (ABA) is an important phytohormone for plant growth, development and responding to stresses such as drought, salinity, and pathogen infection. Pyrabactin Resistance 1 (PYR1)/PYR1-Like (PYL)/Regulatory Component of ABA Receptor (RCAR) (hereafter referred to as PYLs) has been identified as the ABA receptors. The PYL family members have been well studied in many plants. However, the members of PYL family have not been systematically identified at genome level in cultivated tobacco (Nicotiana tabacum) and its two ancestors. In this study, the phylogenic relationships, chromosomal distribution, gene structures, conserved motifs/regions, and expression profiles of NtPYLs were analyzed. We identified 29, 11, 16 PYLs in the genomes of allotetraploid N. tabacum, and its two diploid ancestors N. tomentosiformis and N. sylvestris, respectively. The phylogenetic analysis revealed that NtPYLs can be divided into three subfamilies, and each NtPYL has one counterpart in N. sylvestris or N. tomentosiformis. Based on microarray analysis of NtPYL transcripts, four NtPYLs (from subfamily II, III), and five NtPYLs (from subfamily I) are highlighted as potential candidates for further functional characterization in N. tabacum seed development, response to ABA, and germination, and resistance to abiotic stresses, respectively. Interestingly, the expression profiles of members in the same NtPYL subfamily showed somehow similar patterns in tissues at different developmental stages and in leaves of seedlings under drought stress, suggesting particular NtPYLs might have multiple functions in both plant development and drought stress response. NtPYLs are highlighted for important functions in seed development, germination and response to ABA, and particular in drought tolerance. This work will not only shed light on the PYL family in tobacco, but also provides some valuable information for functional characterization of ABA receptors in N. tabacum.

MADS-box genes play a pivotal role in various processes, including floral and seed development, controlling flowering time, regulation of fruits ripening, and respond to abiotic and biotic stressors in planta. Tobacco (Nicotiana tabacum) has been widely used as a model plant for analyzing the gene function, however, there has been less information on the regulation of flowering, and the associated genes. In the present study, a total of 168 NtMADS-box genes were identified from tobacco, and their phylogenetic relationship, chromosome locations, and gene structures were further analyzed. NtMADS-box genes can be clustered into four sub-families of Mα, Mγ, MIKC*, and MIKC^C. A total of 111 NtMADS-box genes were distributed on 20 chromosomes, and 57 NtMADS-box genes were located on the unanchored scaffolds due to the complex and incomplete assembly of the tobacco genome. Expression profiles of NtMADS-box genes by microarray from 23 different tissues indicated that members in different NtMADS-box gene subfamilies might play specific roles in the growth and flower development, and the transcript levels of 24 NtMADS-box genes were confirmed by quantitative real-time PCR. Importantly, overexpressed NtSOC1/NtMADS133 could promote early flowering and dwarfism in transgenic tobacco plants. Therefore, our findings provide insights on the characterization of NtMADS-box genes to further study their functions in plant development.

Background: Long noncoding RNAs (lncRNAs) have been shown to play important roles in the response of plants to various abiotic stresses, including drought, heat and salt stress. However, the identification and characterization of genome-wide salt-responsive lncRNAs in tobacco (Nicotiana tabacum L.) have been limited. Therefore, this study aimed to identify tobacco lncRNAs in roots and leaves in response to different durations of salt stress treatment. Results: A total of 5,831 lncRNAs were discovered, with 2,428 classified as differentially expressed lncRNAs (DElncRNAs) in response to salt stress. Among these, only 214 DElncRNAs were shared between the 2,147 DElncRNAs in roots and the 495 DElncRNAs in leaves. KEGG pathway enrichment analysis revealed that these DElncRNAs were primarily associated with pathways involved in starch and sucrose metabolism in roots and cysteine and methionine metabolism pathway in leaves. Furthermore, weighted gene co-expression network analysis (WGCNA) identified 15 co-expression modules, with four modules strongly linked to salt stress across different treatment durations (MEsalmon, MElightgreen, MEgreenyellow and MEdarkred). Additionally, an lncRNA-miRNA-mRNA network was constructed, incorporating several known salt-associated miRNAs such as miR156, miR169 and miR396. Conclusions: This study enhances our understanding of the role of lncRNAs in the response of tobacco to salt stress. It provides valuable information on co-expression networks of lncRNA and mRNAs, as well as networks of lncRNAs-miRNAs-mRNAs. These findings identify important candidate lncRNAs that warrant further investigation in the study of plant-environment interactions.

Eleven consecutive N′-n-acylnornicotines from cherry-red tobacco were structurally elucidated and quantitively analyzed using chromatography and mass spectrometry. All of these N′-n-acylnornicotines are first reported in cherry-red tobacco, whereas N′-propionylnornicotine, N′-n-valerylnornicotine, N′-n-nonanoylnornicotine and N′-n-undecanoylnornicotine are first reported in natural products. The concentration distribution of the identified N′-n-acylnornicotines was studied and it was found that N′-n-octanoylnornicotine and N′-n-hexanoylnornicotine showed the highest concentration, accounting for 94% of the detected N′-n-acylnornicotines. The cherry-red color density of the related tobacco leaves was found to be positively correlated with the concentration of the N′-n-acylnornicotines, whereas the ultraviolet–visible spectra of the N′-n-acylnornicotines showed no absorption larger than 300 nm, indicating the discovered compounds are not responsible for the cherry-red color appearance.

Bacterial wilt, caused by the Ralstonia solanacearum species complex, is one of the most damaging bacterial diseases in tobacco and other Solanaceae crops. In this study, we conducted an analysis and comparison of transcriptome landscape changes in seedling roots of three tobacco BC₄F₅ lines, C244, C010, and C035, with different resistance to bacterial wilt at 3, 9, 24, and 48 h after R. solanacearum infection. A number of biological processes were highlighted for their differential enrichment between C244, C010, and C035, especially those associated with cell wall development, protein quality control, and stress response. Hence, we performed a genome-wide identification of seven cell wall development-related gene families and six heat shock protein (Hsp) families and proposed that genes induced by R. solanacearum and showing distinct expression patterns in C244, C010, and C035 could serve as a potential gene resource for enhancing bacterial wilt resistance. Additionally, a comparative transcriptome analysis of R. solanacearum-inoculated root samples from C244 and C035, as well as C010 and C035, resulted in the identification of a further 33 candidate genes, of which Nitab4.5_0007488g0040, a member of the pathogenesis-related protein 1 (PR-1) family, was found to positively regulate bacterial wilt resistance, supported by real-time quantitative PCR (qRT-PCR) and virus-induced gene silencing (VIGS) assays. Our results contribute to a better understanding of molecular mechanisms underlying bacterial wilt resistance and provide novel alternative genes for resistance improvement.