Phenoloxidases: catechol oxidase - the temporary employer and laccase - the rising star of vascular plants.

Phenolics are vital for the adaptation of plants to terrestrial habitats and for species diversity. Phenoloxidases (catechol oxidases, COs, and laccases, LACs) are responsible for the oxidation and polymerization of phenolics. However, their origin, evolution, and differential roles during plant development and land colonization are unclear. We performed the phylogeny, domain, amino acids, compositional biases, and intron analyses to clarify the origin and evolution of COs and LACs, and analysed the structure, selective pressure, and chloroplast targeting to understand the species-dependent distribution of COs. We found that Streptophyta COs were not homologous to the Chlorophyta tyrosinases (TYRs), and might have been acquired by horizontal gene transfer from bacteria. COs expanded in bryophytes. Structural-functionality and selective pressure were partially responsible for the species-dependent retention of COs in embryophytes. LACs emerged in Zygnemaphyceae, having evolved from ascorbate oxidases (AAOs), and prevailed in the vascular plants and strongly expanded in seed plants. COs and LACs coevolved with the phenolic metabolism pathway genes. These results suggested that TYRs and AAOs were the first-stage phenoloxidases in Chlorophyta. COs might be the second key for the early land colonization. LACs were the third one (dominating in the vascular plants) and might be advantageous for diversified phenol substrates and the erect growth of plants. This work provided new insights into how phenoloxidases evolved and were devoted to plant evolution.

Multi-omics analysis reveals the evolutionary origin of diterpenoid alkaloid biosynthesis pathways in Aconitum.

Diterpenoid alkaloids (DAs) have been often utilized in clinical practice due to their analgesic and anti-inflammatory properties. Natural DAs are prevalent in the family Ranunculaceae, notably in the Aconitum genus. Nevertheless, the evolutionary origin of the biosynthesis pathway responsible for DA production remains unknown. In this study, we successfully assembled a high-quality, pseudochromosome-level genome of the DA-rich species Aconitum vilmorinianum (A. vilmorinianum) (5.76 Gb). An A. vilmorinianum-specific whole-genome duplication event was discovered using comparative genomic analysis, which may aid in the evolution of the DA biosynthesis pathway. We identified several genes involved in DA biosynthesis via integrated genomic, transcriptomic, and metabolomic analyses. These genes included enzymes encoding target ent-kaurene oxidases and aminotransferases, which facilitated the activation of diterpenes and insertion of nitrogen atoms into diterpene skeletons, thereby mediating the transformation of diterpenes into DAs. The divergence periods of these genes in A. vilmorinianum were further assessed, and it was shown that two major types of genes were involved in the establishment of the DA biosynthesis pathway. Our integrated analysis offers fresh insights into the evolutionary origin of DAs in A. vilmorinianum as well as suggestions for engineering the biosynthetic pathways to obtain desired DAs.

Polyphenol oxidases regulate pollen development through modulating flavonoids homeostasis in tobacco.

Pollen development is critical in plant reproduction. Polyphenol oxidases (PPOs) genes encode defense-related enzymes, but the role of PPOs in pollen development remains largely unexplored. Here, we characterized NtPPO genes, and then investigated their function in pollen via creating NtPPO9/10 double knockout mutant (cas-1), overexpression 35S::NtPPO10 (cosp) line and RNAi lines against all NtPPOs in Nicotiana tabacum. NtPPOs were abundantly expressed in the anther and pollen (especially NtPPO9/10). The pollen germination, polarity ratio and fruit weights were significantly reduced in the NtPPO-RNAi and cosp lines, while they were normal in cas-1 likely due to compensation by other NtPPO isoforms. Comparisons of metabolites and transcripts between the pollen of WT and NtPPO-RNAi, or cosp showed that decreased enzymatic activity of NtPPOs led to hyper-accumulation of flavonoids. This accumulation might reduce the content of ROS. Ca2+ and actin levels also decreased in pollen of the transgenic lines.Thus, the NtPPOs regulate pollen germination through the flavonoid homeostasis and ROS signal pathway. This finding provides novel insights into the native physiological functions of PPOs in pollen during reproduction.

A YSK-Type Dehydrin from Nicotiana tabacum Enhanced Copper Tolerance in Escherichia coli.

Copper is an essential micronutrient for the maintenance of normal cell function but is toxic in excess. Dehydrins are group two late embryogenesis abundant proteins, which facilitate plant survival in harsh environmental conditions. Here, a YSK-type dehydrin, NtDhn17, was cloned from Nicotiana tabacum under copper toxicity and characterized using a heterologous expression system and in vitro or in vivo experiments and exhibited characteristics of intrinsic disorder during in vitro analyses. Heterologous expression of NtDHN17 enhanced the tolerance of E. coli to various metals, osmotic, and oxidative stress. NtDHN17 showed no Cu2+-binding properties in vivo or in vitro, indicating that metal ion binding is not universal among dehydrins. In vitro and in vivo experiments suggested that NtDHN17 behaved as a potent anti-aggregation agent providing strong protection to aggregated proteins induced by excess copper ions, an effect dependent on the K-segment but not on the Y- or S-segments. In summary, the protective role of NtDHN17 towards E. coli under conditions of copper toxicity may be related to anti-aggregation ability rather than its acting as an ion scavenger, which might be a valuable target for the genetic improvement of resistance to heavy metal stresses in plants.

The complete chloroplast genome of Acer Pubipetiolatum var. pingpienense (Sapindaceae).

The genus Acer is widespread throughout the northern temperate zone, and many species within the genus are of ecological and economical importance. Here we report the newly sequenced chloroplast genome of Acer pubipetiolatum var. pingpienense. This chloroplast genome has a total length of 156,730 bp, and contains a pair of inverted repeats (IRs, 26,743 bp), a large single-copy (LSC) region of 71,582 bp and a small single-copy (SSC) region of 18,092 bp. Phylogenetic analysis suggests that A. pubipetiolatum var. pingpienense is closely related to A. laevigatum, and both fall into Section Palmata. The complete A. pubipetiolatum var. pingpienense chloroplast genome will provide an important genetic resource for future research into the conservation and evolution of this genus. Our findings also suggest that further research is necessary to elucidate the phylogenetic relationships between plant species within this genus.

NtCOMT1 responsible for phytomelatonin biosynthesis confers drought tolerance in Nicotiana tabacum.

Nicotiana tabacum (tobacco) is one of the most important industrial crops and its productivity is vulnerable to drought, particularly in Yunnan province, China due to the long water-deficit spring. Here, we aimed at identifying caffeic acid O-methyltransferase (COMT) in melatonin biosynthesis to provide genetic resources against drought tolerance of tobacco. The integration of the genome-wide identification, phylogenetic relationships, and conserved domain/motif analysis revealed that NtCOMT1 could be the probable functional COMT homolog for melatonin production. In vitro enzyme activity test approved that NtCOMT1 enabled the conversion of N-acetylserotonin into melatonin, occurring both in the cytoplasm and nucleus by subcellular localization analysis. The Km and Vmax values for NtCOMT1 at the optimum temperature (30 °C) were 266.0 µM and 2.155 nmol/min/mg protein. NtCOMT1 was significantly induced by drought stress; whereby if this gene functioned on promoting drought resistance was further conducted. Overexpression of NtCOMT1 resulted in decreased wilting in transgenic tobacco plants subjected to dehydration treatment. The combinatorial effects of NtCOMT1 in increasing melatonin content, inducing antioxidant system, and elevating the expression of drought-related genes could deliver the drought tolerance in tobacco. The characterization of NtCOMT1 may represent a solution to cope with the increasing drought stress in tobacco production in Yunnan province.

Nematicidal Activity of Burkholderia arboris J211 Against Meloidogyne incognita on Tobacco.

Root-knot nematode (Meloidogyne incognita) is the most widespread nematode affecting Solanaceae crops. Due to the lack of effective measures to control this nematode, its management can be achieved, using biocontrol agents. This study investigated in vitro efficacy of the antagonistic bacterial strain J211 isolated from tobacco rhizosphere soil against M. incognita, and further assessed its role in controlling nematodes, both in pot and field trials. Phylogenetic analysis of the 16S rRNA gene sequence of strain J211 assigned to Burkholderia arboris. Culture filtrates B. arboris J211 exhibited anematicidal activity against the second-stage juveniles (J2s) of M. incognita, with a 96.6% mortality after 24 h exposure. Inoculation of J211 in tobacco roots significantly reduced the root galling caused by M. incognita, both in pot and field trials. Meanwhile, plant growth-promoting (PGP) traits results showed that J211 had outstanding IAA-producing activity, and the IAA production reached 66.60 mg L-1. In the field study, B. arboris J211 also promoted tobacco growth and increase flue-cured tobacco yield by 8.7-24.3%. Overall, B. arboris J211 as a high-yielding IAA nematicidal strain effectively controlled M. incognita and improved tobacco yield making it a promising alternative bionematocide.

Grafting: a potential method to reveal the differential accumulation mechanism of secondary metabolites.

Plant secondary metabolites make a great contribution to the agricultural and pharmaceutical industries. Their accumulation is determined by the integrated transport of target compounds and their biosynthesis-related RNA, protein, or DNA. However, it is hard to track the movement of these biomolecules in vivo. Grafting may be an ideal method to solve this problem. The differences in genetic and metabolic backgrounds between rootstock and scion, coupled with multiple omics approaches and other molecular tools, make it feasible to determine the movement of target compounds, RNAs, proteins, and DNAs. In this review, we will introduce methods of using the grafting technique, together with molecular biological tools, to reveal the differential accumulation mechanism of plant secondary metabolites at different levels. Details of the case of the transport of one diterpene alkaloid, fuziline, will be further illustrated to clarify how the specific accumulation model is shaped with the help of grafting and multiple molecular biological tools.

Molecular mechanisms and evolutionary history of phytomelatonin in flowering.

Flowering is a critical stage in plant life history, which is coordinated by environmental signals and endogenous cues. Phytomelatonin is a widely distributed indoleamine present in all living organisms and plays pleiotropic roles in plant growth and development. Recent evidence has established that phytomelatonin could modulate flowering in many species, probably in a concentration-dependent manner. Phytomelatonin seems to associate with floral meristem identification and floral organ formation, and the fluctuation of phytomelatonin might be important for flowering. Regarding the underlying mechanisms, phytomelatonin interacts with the central components of floral gene regulatory networks directly or indirectly, including the MADS-box gene family, phytohormones, and reactive oxygen species (ROS). From an evolutionary point of view, the actions of phytomelatonin in flowering probably evolved during the period of the diversification of flowering plants and could be regarded as a functional extension of its primary activities. The presumed evolutionary history of phytomelatonin-modulated flowering is proposed, presented in the chronological order of the appearance of phytomelatonin and core flowering regulators, namely DELLA proteins, ROS, and phytohormones. Further efforts are needed to address some intriguing aspects, such as the exploration of the association between phytomelatonin and photoperiodic flowering, phytomelatonin-related floral MADS-box genes, the crosstalk between phytomelatonin and phytohormones, as well as its potential applications in agriculture.

Development of an RT-LAMP assay for the detection of maize yellow mosaic virus in maize.

Maize is one of the most widely cultivated cereal crops worldwide. Maize yellow mosaic virus (MaYMV) (species Maize yellow mosaic virus, genus Polerovirus and family Luteoviridae) was first reported in maize from China. In this study, a one-step reverse-transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed for detecting MaYMV. The optimal concentrations of betaine, Mg2+ and dNTPs for the assay were 0 M, 1.4 mM and 6 mM, respectively, and the optimal reaction time was 50 min. Using total plant RNA as the template, the detection limit of the RT-LAMP assay for MaYMV was 1 pg, while that of RT-PCR was 100 pg, indicating that the RT-LAMP assay developed was 100 times more sensitive than RT-PCR. Importantly, the RT-LAMP assay successfully detected MaYMV using rapidly extracted crude RNA from infected maize as a template. In conclusion, the RT-LAMP assay developed was a rapid, specific, sensitive and low-cost method for the detection of MaYMV in field samples of maize.

Simultaneous multiplex RT-PCR detection of four viruses associated with maize lethal necrosis disease.

Maize lethal necrosis disease (MLND) is a serious disease of worldwide importance. It is caused by the co-infection of maize with maize chlorotic mottle virus (MCMV) and a potyvirus, such as sugarcane mosaic virus (SCMV), that acts synergistically to produce more severe symptoms and production losses. More recently, maize yellow mosaic virus (MaYMV) and maize-associated totivirus (MATV) were found to co-infect with MCMV and SCMV in maize plants. To facilitate the detection of these viruses in co-infected maize, a multiplex RT-PCR assay was developed in this study. The assay used five specific primer pairs and simultaneously amplified these four viruses as well as the elongation factor 1α (EF 1α) gene use as internal control in one tube. The concentration of the primers, annealing temperature, annealing time, extension time and amplification cycles were optimized for the multiplex RT-PCR. The detection limit of the assay was up to 100 pg of total cDNA template. This multiplex RT-PCR assay was shown to be a sensitive and effective tool for the screening of field samples for the presence of these viruses in co-infected maize.

Identification, Biological Activities and Biosynthetic Pathway of Dendrobium Alkaloids.

Dendrobium is a genus of flowering plants belonging to the Orchidaceae family with more than 1,400 species. Many Dendrobium species have been used as medicinal plants in several Asian countries for thousands of years. Alkaloids were reported as the major biological markers due to their complex chemical compositions and various types. In this review, we summarized the structural types of alkaloids, their pharmacological activities, as well as the mechanisms of biological activities. More than sixty alkaloids were isolated and identified from the Dendrobium genus. Moreover, the pharmacological effects of Dendrobium alkaloids as hepatic lipid and gluconeogenesis regulation, as neuroprotection, and as anti-tumor, anti-inflammatory, anti-diabetes, and anti-virus factors were described. Besides, the total chemical synthesis of dendrobine is provided, while the biosynthetic pathway of dendrobine has been proposed based on the functions of associated genes. For applications of these invaluable herbs, more researches on the extraction of biological markers from compounds are needed. Further confirmation of the proposed biosynthetic pathways is anticipated as well.

Genomic characterization and expression profiles of stress-associated proteins (SAPs) in castor bean (Ricinus communis).

Stress-associated proteins (SAPs) are known as response factors to multiple abiotic and biotic stresses in plants. However, the potential physiological and molecular functions of SAPs remain largely unclear. Castor bean (Ricinus communis L.) is one of the most economically valuable non-edible woody oilseed crops, able to be widely cultivated in marginal lands worldwide because of its broad adaptive capacity to soil and climate conditions. Whether SAPs in castor bean plays a key role in adapting diverse soil conditions and stresses remains unknown. In this study, we used the castor bean genome to identify and characterize nine castor bean SAP genes (RcSAP). Structural analysis showed that castor bean SAP gene structures and functional domain types vary greatly, differing in intron number, protein sequence, and functional domain type. Notably, the AN1-C2H2-C2H2 zinc finger domain within RcSAP9 has not been often observed in other plant families. High throughput RNA-seq data showed that castor bean SAP gene profiles varied among different tissues. In addition, castor bean SAP gene expression varied in response to different stresses, including salt, drought, heat, cold and ABA and MeJA, suggesting that the transcriptional regulation of castor bean SAP genes might operate independently of each other, and at least partially independent from ABA and MeJA signal pathways. Cis-element analyses for each castor bean SAP gene showed that no common cis-elements are shared across the nine castor bean SAP genes. Castor bean SAPs were localized to different regions of cells, including the cytoplasm, nucleus, and cytomembrane. This study provides a comprehensive profile of castor bean SAP genes that advances our understanding of their potential physiological and molecular functions in regulating growth and development and their responses to different abiotic stresses.

Melatonin synthesis genes N-acetylserotonin methyltransferases evolved into caffeic acid O-methyltransferases and both assisted in plant terrestrialization.

Terrestrialization is one of the most momentous events in the history of plant life, which leads to the subsequent evolution of plant diversity. The transition species, in this process, had to acquire a range of adaptive mechanisms to cope with the harsh features of terrestrial environments compared to that of aquatic habitat. As an ancient antioxidant, a leading regulator of ROS signaling or homeostasis, and a presumed plant master regulator, melatonin likely assisted plants transition to land and their adaption to terrestrial ecosystems. N-acetylserotonin methyltransferases (ASMT) and caffeic acid O-methyltransferases (COMT), both in the O-methyltransferase (OMT) family, catalyze the core O-methylation reaction in melatonin biosynthesis. How these two enzymes with close relevance evolved in plant evolutionary history and whether they participated in plant terrestrialization remains unknown. Using combined phylogenetic evidence and protein structure analysis, it is revealed that COMT likely evolved from ASMT by gene duplication and subsequent divergence. Newly emergent COMT gained a significantly higher ASMT activity to produce greater amounts of melatonin for immobile plants to acclimate to the stressful land environments after evolving from the more environmentally-stable aquatic conditions. The COMT genes possess more conserved substrate-binding sites at the amino acid level and more open protein conformation compared to ASMT, and getting a new function to catalyze the lignin biosynthesis. This development directly contributed to the dominance of vascular plants among the Earth's flora and prompted plant colonization of land. Thus, ASMT, together with its descendant COMT, might play key roles in plant transition to land. The current study provides new insights into plant terrestrialization with gene duplication contributing to this process along with well-known horizontal gene transfer.

Penicillium chrysogenum polypeptide extract protects tobacco plants from tobacco mosaic virus infection through modulation of ABA biosynthesis and callose priming.

The polypeptide extract of the dry mycelium of Penicillium chrysogenum (PDMP) can protect tobacco plants from tobacco mosaic virus (TMV), although the mechanism underlying PDMP-mediated TMV resistance remains unknown. In our study, we analysed a potential mechanism via RNA sequencing (RNA-seq) and found that the abscisic acid (ABA) biosynthetic pathway and ß-1,3-glucanase, a callose-degrading enzyme, might play an important role in PDMP-induced priming of resistance to TMV. To test our hypothesis, we successfully generated a Nicotiana benthamiana ABA biosynthesis mutant and evaluated the role of the ABA pathway in PDMP-induced callose deposition during resistance to TMV infection. Our results suggested that PDMP can induce callose priming to defend against TMV movement. PDMP inhibited TMV movement by increasing callose deposition around plasmodesmata, but this phenomenon did not occur in the ABA biosynthesis mutant; moreover, these effects of PDMP on callose deposition could be rescued by treatment with exogenous ABA. Our results suggested that callose deposition around plasmodesmata in wild-type plants is mainly responsible for the restriction of TMV movement during the PDMP-induced defensive response to TMV infection, and that ABA biosynthesis apparently plays a crucial role in PDMP-induced callose priming for enhancing defence against TMV.

Melatonin confers heavy metal-induced tolerance by alleviating oxidative stress and reducing the heavy metal accumulation in Exophiala pisciphila, a dark septate endophyte (DSE).

BACKGROUND: Melatonin (MT), ubiquitous in almost all organisms, functions as a free radical scavenger. Despite several reports on its role as an antioxidant in animals, plants, and some microorganisms, extensive studies in filamentous fungi are limited. Based upon the role of melatonin as an antioxidant, we investigated its role in heavy metal-induced stress tolerance in Exophiala pisciphila, a dark septate endophyte (DSE), by studying the underlying mechanisms in alleviating oxidative stress and reducing heavy metal accumulation. RESULTS: A significant decrease in malondialdehyde (MDA) and oxygen free radical (OFR) in E. pisciphila was recorded under Cd, Zn, and Pb stresses as compared to the control. Pretreatment of E. pisciphila with 200.0 µM exogenous melatonin significantly increased the activity of superoxide dismutase (SOD) under Zn and Pb stresses. Pretreatment with 200.0 µM melatonin also lowered Cd, Zn, and Pb concentrations significantly. Melatonin production was enhanced by Cd, Cu, and Zn after 2 d, and melatonin biosynthetic enzyme genes, E. pisciphila tryptophan decarboxylase (EpTDC1) and serotonin N-acetyltransferase (EpSNAT1), were transcriptionally upregulated. The overexpression of EpTDC1 and N-acetylserotonin O-methyltransferase (EpASMT1) in Escherichia coli and Arabidopsis thaliana enhanced its heavy metal-induced stress tolerance. The overexpression of EpTDC1 and EpASMT1 reduced the Cd accumulation in the whole A. thaliana plants, especially in the roots. CONCLUSIONS: Melatonin conferred heavy metal-induced stress tolerance by alleviating oxidative stress, activating antioxidant enzyme SOD, and reducing heavy metal accumulation in E. pisciphila. Melatonin biosynthetic enzyme genes of E. pisciphila also played key roles in limiting excessive heavy metal accumulation in A. thaliana. These findings can be extended to understand the role of melatonin in other DSEs associated with economically important plants and help develop new strategies in sustainable agriculture practice where plants can grow in soils contaminated with heavy metals.

Phytomelatonin: An Emerging Regulator of Plant Biotic Stress Resistance.

Melatonin has diverse functions in plant development and stress tolerance, with recent evidence showing a beneficial role in plant biotic stress tolerance. It has been hypothesized that pathogenic invasion causes the immediate generation of melatonin, reactive oxygen species (ROS), and reactive nitrogen species (RNS), with these being mutually dependent, forming the integrative melatonin-ROS-RNS feedforward loop. Here we discuss how the loop, possibly located in the mitochondria and chloroplasts, maximizes disease resistance in the early pathogen ingress stage, providing on-site protection. We also review how melatonin interacts with phytohormone signaling pathways to mediate defense responses and discuss the evolutionary context from the beginnings of the melatonin receptor-mitogen-activated protein kinase (MAPK) cascade in unicellular green algae, followed by the occurrence of phytohormone pathways in land plants.

Solanum steroidal glycoalkaloids: structural diversity, biological activities, and biosynthesis.

Covering: up to 1 October 2020Solanum steroidal glycoalkaloids (SGA), characterized by nitrogenous steroidal aglycone and glycoside residues, mainly occur in the Solanum species, including economically important edible plants such as potato, tomato, and eggplant. To date, 107 SGA assigned to six total skeletons have been identified from Solanum plants. SGA have unique structures and display significant pharmacological activities such as cytotoxic, antimicrobial, anticholesterol, and some are well-known poisons. The biosynthesis pathway, transcriptional regulation, and the evolution of SGA are also examined in detail. This report updates the chemical knowledge of the naturally occurring SGA from Solanum species, thereby providing an in-depth analysis of their diversity, biological activities, and biosynthesis.

NaKTI2, a Kunitz trypsin inhibitor transcriptionally regulated by NaWRKY3 and NaWRKY6, is required for herbivore resistance in Nicotiana attenuata.

KEY MESSAGE: Here, we reported that a pathogen- and herbivore-induced Kunitz trypsin inhibitor gene, NaKTI2, is required for herbivore resistance, and transcriptionally regulated mainly by NaWRKY3 and NaWRKY6 but not Jasmonate signaling. Plant protease inhibitor (PI) occurs widely in plant species, and is considered as an important part of plant defense arsenal against herbivores. Transcriptome analysis of Nicotiana attenuata leaves revealed that a Kunitz trypsin inhibitor gene, NaKTI2, was highly elicited after inoculation of Alternaria alternata (tobacco pathotype). However, the roles of NaKTI2 in pathogen- and herbivore resistance and its regulation were unclear. NaKTI2 had typical domains of Kunitz trypsin inhibitors and exhibited a high level of trypsin protease inhibitor activities when transiently over-expressed. The transcripts of NaKTI2 could be induced by A. alternata and Spodoptera litura oral secretions (OS). Silencing NaKTI2 via virus-induced gene silencing technique has no influence on lesion diameters developed on N. attenuata leaves after A. alternata inoculation, but S. litura larvae gained more mass and had higher survivorship on NaKTI2-silenced plants. Meanwhile, the expression of NaPI, a PI gene essential for herbivore resistance previously identified in N. attenuata, was not affected in NaKTI2-silenced plants. Unlike NaPI, which was predominantly regulated by jasmonate (JA) signaling, OS-elicited NaKTI2 transcripts were only slightly reduced in JA-deficient plants, but were dramatically decreased in NaWRKY3- and NaWRKY6- silenced plants, respectively. Further electromobility shift assays indicated that NaWRKY3 and NaWRKY6 could directly bind to the promoter regions of NaKTI2 in vitro. Taken together, our results demonstrate that in addition to NaPI, NaKTI2, a pathogen- and herbivore-induced Kunitz trypsin inhibitor gene, is also required for herbivore resistance, and mainly regulated by NaWRKY3 and NaWRKY6.

Genome-Wide Identification and Expression Profile of the SNAT Gene Family in Tobacco (Nicotiana tabacum).

Melatonin plays key roles in development and confers stress tolerance to plants. Serotonin N-acetyltransferase (SNAT) is either the enzyme involved in the last step or the penultimate enzyme of phytomelatonin biosynthesis. To date, SNAT genes have not been characterized in tobacco (Nicotiana tabacum), an economically important plant species. The sequence of the Acetyltransf_7 conserved domain was used as a query sequence, and 12 NtSNAT candidate genes were in turn identified in the genome of tobacco. These NtSNATs could be divided into two groups based on the phylogenetic tree. NtSNAT1 and NtSNAT2 clustered together with the other typical SNATs, but the other 10 NtSNATs separately clustered outside of the typical SNATs. These 10 NtSNATs have only motif 1, whereas representative SNATs, such as NtSNAT1 and NtSNAT2 or a SNAT from cyanobacteria, have five motifs. In addition, NtSNAT1 and NtSNAT2 are highly homologous to the characterized OsSNAT1, 62.95 and 71.36%, respectively; however, the homology between the other 10 NtSNAT genes and OsSNAT1 is low. Concomitantly, it is hypothesized that NtSNAT1 and NtSNAT2 are the homolog of SNATs, whereas the other 10 candidates could be considered NtSNAT-like genes. Furthermore, both Nicotiana tomentosiformis and Nicotiana sylvestris, two diploid ancestor species of N. tabacum, have two SNAT candidates; therefore, it is speculated that gene rearrangement or deletion during the process of genomic stabilization after whole-genome duplication or polyploidization led to the preservation of NtSNAT1 and NtSNAT2 during the evolution of tobacco from the ancestral diploid to the allotetraploid. NtSNAT and NtSNAT-like genes were differentially expressed in all organs under different stress conditions, indicating that these genes potentially associated with plant growth and development and stress resistance. Under different stress conditions, the expression of NtSNAT1 was significantly upregulated upon high-temperature and cadmium stresses, while the expression of NtSNAT2 did not significantly increase under any of the tested stress treatments. These results provide valuable information for elucidating the evolutionary relationship of SNAT genes in tobacco and genetic resources for improving tobacco production in the future.