NAM, ATAF, And CUC Research Articles

The transcription factor VaNAC17 from grapevine (Vitis amurensis) enhances drought tolerance by modulating jasmonic acid biosynthesis in transgenic Arabidopsis.

Expression of VaNAC17 improved drought tolerance in transgenic Arabidopsis by upregulating stress-responsive genes, modulating JA biosynthesis, and enhancing ROS scavenging. Water deficit severely affects the growth and development of plants such as grapevine (Vitis spp.). Members of the NAC (NAM, ATAF1/2, and CUC2) transcription factor (TF) family participate in drought-stress-induced signal transduction in plants, but little is known about the roles of NAC genes in drought tolerance in grapevine. Here, we explored the role of VaNAC17 in Vitis amurensis, a cold-hardy, drought-tolerant species of grapevine. VaNAC17 was strongly induced in grapevine by drought, exogenous abscisic acid (ABA), and methyl jasmonate (MeJA). A transient expression assay in yeast indicated that VaNAC17 functions as a transcriptional activator. Notably, heterologous expression of VaNAC17 in Arabidopsis thaliana enhanced drought tolerance. VaNAC17-expressing Arabidopsis plants showed decreased reactive oxygen species (ROS) accumulation compared to wild-type plants under drought conditions. RNA-seq analysis indicated that VaNAC17 expression increased the transcription of downstream stress-responsive genes after 5days of drought treatment, especially genes involved in jasmonic acid (JA) biosynthesis (such as LOX3, AOC1 and OPR3) and signaling (such as MYC2, JAZ1, VSP1 and CORI3) pathways. Endogenous JA levels increased in VaNAC17-OE plants under drought stress. Taken together, these results indicate that VaNAC17 plays a positive role in drought tolerance by modulating endogenous JA biosynthesis and ROS scavenging.

A novel NAC transcription factor, MdNAC42, regulates anthocyanin accumulation in red-fleshed apple by interacting with MdMYB10.

Anthocyanin pigmentation is an important consumption trait of apple (Malus domestica Borkh.). In this study, we focused on the identification of NAC (NAM, ATAF1/2 and CUC2) proteins involved in the regulation of anthocyanin accumulation in apple flesh. A group of MdNACs was selected for comparison of expression patterns between the white-fleshed cultivar 'Granny Smith' and red-fleshed 'Redlove'. Among them, MdNAC42 was screened, which exhibited a higher expression level in red-fleshed than in white-fleshed fruit, and has a positive correlation with anthocyanin content as fruits ripened. Moreover, overexpression of MdNAC42 in apple calli resulted in the up-regulation of flavonoid pathway genes, including MdCHS, MdCHI, MdF3H, MdDFR, MdANS and MdUFGT, thereby increasing the accumulation of anthocyanins, which confirmed the roles of MdNAC42 in anthocyanin biosynthesis. Notably, MdNAC42 was demonstrated to have an obvious interaction with MdMYB10 either in vitro or in vivo by yeast two-hybrid combined with bimolecular fluorescence complementation, further suggesting that MdNAC42 is an important part of the regulatory network controlling the anthocyanin pigmentation of red-fleshed apples. To the best of our knowledge, this is the first report identifying the MdNAC gene as related to anthocyanin accumulation in red-fleshed apples. This study provides valuable information for improving the regulatory model of anthocyanin biosynthesis in apple fruit.

Molecular and Functional Characterization of CaNAC035, an NAC Transcription Factor From Pepper (Capsicum annuum L.).

NAC (NAM, ATAF1/2, and CUC2) proteins are the plant-specific transcription factors (TFs) which are important in plant response to abiotic stresses. However, knowledge about the functional role that NACs play in pepper abiotic stress tolerance is limited. In this study, we isolated a NAC TF gene, CaNAC035, from pepper (Capsicum annuum L.), where the protein is localized in the nucleus and functions as a transcriptional activator. CaNAC035 expression is induced by low and high temperatures, osmotic stress, salt, gibberellic acid (GA), methyl-jasmonic acid (MeJA), salicylic acid (SA), and abscisic acid (ABA). To understand the function of CaNAC035 in the abiotic stress responsep, we used virus-induced gene silencing in pepper to knockdown the CaNAC035 and overexpressed the CaNAC035 in Arabidopsis. The results showed that pepper seedlings in which CaNAC035 was silenced, showed more damage than the control pepper plants after cold, NaCl, and mannitol treatments. Correspondingly increased electrolyte leakage, a higher level of malondialdehyde (MDA), H2O2, and superoxide radicals were found after cold treatments. CaNAC035-silenced seedlings exhibited lower chlorophyll content while CaNAC035-overexpressed Arabidopsis plants had higher germination rate and fresh weight after mannitol and NaCl treatments. We also reported 18 proteins that potentially interact with CaNAC035 and may participate in processes such as the stress response, resistance, and photosynthesis. Our results suggest that CaNAC035 is a positive regulator of abiotic stress tolerance in pepper which acts through multiple signaling pathways.

Genome-Wide Analysis of the NAC Domain Transcription Factor Gene Family in Theobroma cacao.

As a plant-specific transcription factor, the NAC (NAM, ATAF1/2 and CUC2) domain protein plays an important role in plant growth and development, as well as stress resistance. Based on the genomic data of the cacao tree, this study identified 102 cacao NAC genes and named them according to their location within the genome. The phylogeny of the protein sequence of the cacao tree NAC family was analyzed using various bioinformatic methods, and then divided into 12 subfamilies. Then, the amino-acid composition, physicochemical properties, genomic location, gene structure, conserved domains, and promoter cis-acting elements were analyzed. This study provides information on the evolution of the TcNAC gene and its possible functions, laying the foundation for further research on the NAC family.

Involvement of VNS NAC-domain transcription factors in tracheid formation in Pinus taeda.

Vascular plants have two types of water-conducting cells, xylem vessel cells (in angiosperms) and tracheid cells (in ferns and gymnosperms). These cells are commonly characterized by secondary cell wall (SCW) formation and programmed cell death (PCD), which increase the efficiency of water conduction. The differentiation of xylem vessel cells is regulated by a set of NAC (NAM, ATAF1/2 and CUC2) transcription factors, called the VASCULAR-RELATED NAC-DOMAIN (VND) family, in Arabidopsis thaliana Linne. The VNDs regulate the transcriptional induction of genes required for SCW formation and PCD. However, information on the transcriptional regulation of tracheid cell differentiation is still limited. Here, we performed functional analysis of loblolly pine (Pinus taeda Linne) VND homologs (PtaVNS, for VND, NST/SND, SMB-related protein). We identified five PtaVNS genes in the loblolly pine genome, and four of these PtaVNS genes were highly expressed in tissues with tracheid cells, such as shoot apices and developing xylem. Transient overexpression of PtaVNS genes induced xylem vessel cell-like patterning of SCW deposition in tobacco (Nicotiana benthamiana Domin) leaves, and up-regulated the promoter activities of loblolly pine genes homologous to SCW-related MYB transcription factor genes and cellulose synthase genes, as well as to cysteine protease genes for PCD. Collectively, our data indicated that PtaVNS proteins possess transcriptional activity to induce the molecular programs required for tracheid formation, i.e., SCW formation and PCD. Moreover, these findings suggest that the VNS-MYB-based transcriptional network regulating water-conducting cell differentiation in angiosperm and moss plants is conserved in gymnosperms.

The NAC transcription factor CaNAC064 is a regulator of cold stress tolerance in peppers

NAC (NAM, ATAF1/2 and CUC2) proteins are plant-specific transcription factors (TFs) that are important in plant abiotic stress responses. In this study we isolated a NAC gene from Capsicum annuum leaves, designated as CaNAC064. We characterized the amino acid sequence of CaNAC064 and found that it contain conserved domains of the NAC family, including a highly conserved N-terminus domain and a highly variable C-terminus domain. Expression analysis showed that the 40C, 400C, salicylic acid (SA) and abscisic acid (ABA) treatments strongly induced the expression of CaNAC064 through silencing of CaNAC064 in pepper and overexpressing in Arabidopsis. CaNAC064-silenced pepper plants exhibited more serious wilting, higher MDA contents and chilling injury index, lower proline content, and more accumulation of ROS in the leaves after cold stress. The CaNAC064-overexpressing Arabidopsis plants exhibited lower MDA content, chilling injury index and relative electrolyte leakage content as compared to WT plants under cold stress. Transcriptional activation activity analysis indicated that CaNAC064 has transcriptional activation activity in the 691–1071 bp key region. We identified 45 proteins that putatively interact with CaNAC064 using the Yeast Two-Hybrid method. According to the Yeast Two-Hybrid and BIFC results, CaNAC064 interacted with low temperature-induced haplo-proteinase proteins in plant cell. These results suggested that CaNAC064 positively modulates plant cold-tolerance, laying the foundation for future investigations into the role of NACs as regulatory proteins of cold tolerance in plants.

Genome-Wide Investigation of the NAC Gene Family and Its Potential Association with the Secondary Cell Wall in Moso Bamboo

NAC (NAM, ATAF, and CUC) transcription factors (TFs) are implicated in the transcriptional regulation of diverse processes and have been characterized in a number of plant species. However, NAC TFs are still not well understood in bamboo, especially their potential association with the secondary cell wall (SCW). Here, 94 PeNACs were identified and characterized in moso bamboo (Phyllostachys edulis). Based on their gene structures and conserved motifs, the PeNACs were divided into 11 groups according to their homologs in Arabidopsis. PeNACs were expressed variously in different tissues of moso bamboo, suggesting their functional diversity. Fifteen PeNACs associated with the SCW were selected for co-expression analysis and validation. It was predicted that 396 genes were co-expressed with the 15 PeNACs, in which 16 and 55 genes were involved in the lignin catabolic process and cellulose biosynthetic process respectively. As the degree of lignification in the growing bamboo shoots increased, all 15 PeNACs were upregulated with a trend of rising first and then decreasing except PeNAC37, which increased continuously. These results indicated that these PeNACs might play important roles in SCW biosynthesis and lignification in bamboo shoots. Seven of 15 PeNACs had been found positively co-expressed with seven PeMYBs, and they had similar expression patterns with those of the PeMYBs in bamboo shoots. The targeted sites of miR164 were found in 16 PeNACs, of which three PeNACs associated with SCW were validated to have an opposite expression trend to that of miR164 in growing bamboo shoots. In addition, three PeNACs were selected and verified to have self-activation activities. These results provide comprehensive information of the NAC gene family in moso bamboo, which will be helpful for further functional studies of PeNACs to reveal the molecular regulatory mechanisms of bamboo wood property.

Transcriptome profiling of postharvest shoots identifies PheNAP2- and PheNAP3-promoted shoot senescence.

The juvenile shoots of Phyllostachys edulis have been used as a food source for thousands of years, and it is recognized as a potential source of nutraceuticals. However, its rapid senescence restricts bamboo production and consumption, and the underlying molecular mechanisms of rapid shoot senescence remain largely unclear. In the present study, transcriptome profiling was employed to investigate the molecular regulation of postharvest senescence in shoots, along with physiological assays and anatomical dissections. Results revealed a distinct shift in expression postharvest, specifically transitions from cellular division and differentiation to the relocation of nutrients and programmed cell death. A number of regulatory and signaling factors were induced during postharvest senescence. Moreover, transcription factors, including NAM, ATAF and CUC (NAC) transcription factors, basic helix-loop-helix transcription factors, basic region/leucine zipper transcription factors, MYB transcription factors and WRKY transcription factors, were critical for shoot postharvest senescence, of which NACs were the most abundant. PheNAP2 and PheNAP3 were induced in postharvest shoots and found to promote leaf senescence in Arabidopsis by inducing the expression of AtSAG12 and AtSAG113. PheNAP2 and PheNAP3 could both restore the stay-green Arabidopsis nap to the wild-type phenotype either under normal growth condition or under abscisic acid treatment. Collectively, these results suggest that PheNAPs may promote shoot senescence. These findings provide a systematic view of shoot senescence and will inform future studies on the underlying molecular mechanisms responsible for shoot degradation during storage.

Genome-Wide Analysis of NAC Gene Family in Betula pendula

NACs (NAM, ATAF1/2, and CUC2) are plant-specific transcription factors that play diverse roles in various plant developmental processes. In this study, we identified the NAC gene family in birch (Betula pendula) and further analyzed the function of BpNACs. Phylogenetic analysis reveals that the 114 BpNACs can be divided into seven subfamilies. We investigated the expression levels of these BpNACs in different tissues of birch including roots, xylem, leaves, and flowers, and the results showed that the BpNACs seem to be expressed higher in xylem and roots than leaves and flowers. In addition to tissue-specific expression analysis, we investigated the expression of BpNACs under low-temperature stress. A total of 21 BpNACs were differentially expressed under low-temperature stress, of which 17 were up-regulated, and four were down-regulated. Using the gene expression data, we reconstructed the gene co-expression network for the 21 low-temperature-responsive BpNACs. In conclusion, our results provide insight into the evolution of NAC genes in the B. pendula genome, and provide a basis for understanding the molecular mechanism for BpNAC-mediated cold responses in birch.

PtrARF2.1 Is Involved in Regulation of Leaf Development and Lignin Biosynthesis in Poplar Trees.

Auxin response factors (ARFs) are important regulators modulating the expression of auxin-responsive genes in various biological processes in plants. In the Populus genome, a total of 39 ARF members have been identified, but their detailed functions are still unclear. In this study, six poplar auxin response factor 2 (PtrARF2) members were isolated from P. trichocarpa. Expression pattern analysis showed that PtrARF2.1 is highly expressed in leaf tissues compared with other PtrARF2 genes and significantly repressed by exogenous auxin treatment. PtrARF2.1 is a nuclear-localized protein without transcriptional activation activity. Knockdown of PtrARF2.1 by RNA interference (RNAi) in poplars led to the dwarf plant, altered leaf shape, and reduced size of the leaf blade, while overexpression of PtrARF2.1 resulted in a slight reduction in plant height and the similar leaf phenotype in contrast to the wildtype. Furthermore, histological staining analysis revealed an ectopic deposition of lignin in leaf veins and petioles of PtrARF2.1-RNAi lines. RNA-Seq analysis showed that 74 differential expression genes (DEGs) belonging to 12 transcription factor families, such as NAM, ATAF and CUC (NAC), v-myb avian myeloblastosis viral oncogene homolog (MYB), ethylene response factors (ERF) and basic helix–loop–helix (bHLH), were identified in PtrARF2.1-RNAi leaves and other 24 DEGs were associated with the lignin biosynthetic pathway. Altogether, the data indicate that PtrARF2.1 plays an important role in regulating leaf development and influences the lignin biosynthesis in poplars.

LBD29-Involved Auxin Signaling Represses NAC Master Regulators and Fiber Wall Biosynthesis.

NAM, ATAF1/2 and CUC2 (NAC) domain transcription factors function as master switches in regulating secondary cell wall (SCW) biosynthesis in Arabidopsis (Arabidopsis thaliana) stems. Despite the importance of these NACs in fiber development, the upstream signal is still elusive. Using a large-scale mutant screening, we identified a dominant activation-tagging mutant, fiberless-d (fls-d), showing defective SCW development in stem fibers, similar to that of the nac secondary wall thickening promoting factor1-1 (nst1-1)nst3-3 double mutant. Overexpression of LATERAL ORGAN BOUNDARIES DOMAIN29 (LBD29) is responsible for the fls-d mutant phenotypes. By contrast, loss-of-function of LBD29, either in the dominant repression transgenic lines or in the transfer-DNA (T-DNA) insertion mutant lbd29-1, enhanced SCW development in fibers. Genetic analysis and transgenic studies demonstrated LBD29 depends on master regulators in mediating SCW biosynthesis, specifically NAC SECONDARY WALL THICKENING PROMOTING FACTOR1 (NST1), NST2, and NST3. Increasing indole-3-acetic acid (IAA) levels, either in stem tissues above a N-1-naphthylphthalamic acid-treated region or in plants directly sprayed with IAA, inhibits fiber wall thickening. The inhibition effect of naphthylphthalamic acid treatment and exogenous IAA application depends on a known auxin signaling pathway involving AUXIN RESPONSE FACTOR7 (ARF7)/ARF19 and LBD29. These results demonstrate auxin is upstream of LBD29 in repressing NAC master regulators, and therefore shed new light on the regulation of SCW biosynthesis in Arabidopsis.

The NAC Protein from Tamarix hispida, ThNAC7, Confers Salt and Osmotic Stress Tolerance by Increasing Reactive Oxygen Species Scavenging Capability.

Plant specific NAC (NAM, ATAF1/2 and CUC2) transcription factors (TFs) play important roles in response to abiotic stress. In this study, we identified and characterized a NAC protein, ThNAC7, from Tamarix hispida. ThNAC7 is a nuclear localized protein and has transcriptional activation activity. ThNAC7 expression was markedly induced by salt and osmotic stresses. Transiently transformed T. hispida seedlings overexpressing ThNAC7 (OE) or with RNA interference (RNAi) silenced ThNAC7 were generated to investigate abiotic stress tolerance via the gain- and loss- of function. Overexpressing ThNAC7 showed an increased reactive oxygen species (ROS) scavenging capabilities and proline content, which was accomplished by enhancing the activities of superoxide dismutase (SOD) and peroxidase (POD) in transiently transformed T. hispida and stably transformed Arabidopsis plants. Additionally, ThNAC7 activated these physiological changes by regulating the transcription level of P5CS, SOD and POD genes. RNA-sequencing (RNA-seq) comparison between wild-type and ThNAC7-transformed Arabidopsis showed that more than 40 known salt tolerance genes might regulated by ThNAC7, including stress tolerance-related genes and TF genes. The results indicated that ThNAC7 induces the transcription level of genes associated with stress tolerance to enhance salt and osmotic stress tolerance via an increase in osmotic potential and enhanced ROS scavenging.

Genome-Wide Identification, Characterization, and Expression Analysis of the NAC Transcription Factor in Chenopodium quinoa.

The NAC (NAM, ATAF, and CUC) family is one of the largest families of plant-specific transcription factors. It is involved in many plant growth and development processes, as well as abiotic/biotic stress responses. So far, little is known about the NAC family in Chenopodium quinoa. In the present study, a total of 90 NACs were identified in quinoa (named as CqNAC1-CqNAC90) and phylogenetically divided into 14 distinct subfamilies. Different subfamilies showed diversities in gene proportions, exon–intron structures, and motif compositions. In addition, 28 CqNAC duplication events were investigated, and a strong subfamily preference was found during the NAC expansion in quinoa, indicating that the duplication event was not random across NAC subfamilies during quinoa evolution. Moreover, the analysis of Ka/Ks (non-synonymous substitution rate/synonymous substitution rate) ratios suggested that the duplicated CqNACs might have mainly experienced purifying selection pressure with limited functional divergence. Additionally, 11 selected CqNACs showed significant tissue-specific expression patterns, and all the CqNACs were positively regulated in response to salt stress. The result provided evidence for selecting candidate genes for further characterization in tissue/organ specificity and their functional involvement in quinoa’s strong salinity tolerance.

LcNAC13 Physically Interacts with LcR1MYB1 to Coregulate Anthocyanin Biosynthesis-Related Genes during Litchi Fruit Ripening.

Anthocyanin accumulation is crucial for the development of quality for most fruit. The mechanism underlying the regulation of anthocyanin biosynthesis by transcription factors in litchi fruit remains largely unknown. In this study, we isolated one NAC (NAM, ATAF1/2 and CUC2) TF gene, LcNAC13. Expression of LcNAC13 was upregulated as ripening proceeded, followed by the accumulation of anthocyanins. Electrophoretic mobility shift assay (EMSA) and transient expression assay showed that LcNAC13 could negatively regulate the expression of anthocyanin biosynthesis-related genes, including LcCHS1/2, LcCHI, LcF3H, LcF3’H, LcDFR, and LcMYB1. Furthermore, LcR1MYB1, as one R1-MYB type MYB, was identified to physically interact with LcNAC13 and reverse the effect of LcNAC13. Taken together, these results suggested that LcNAC13 and LcR1MYB1 may act together to antagonistically regulate anthocyanin biosynthesis during litchi fruit ripening, which helps to provide new insights into the regulatory networks of anthocyanin biosynthesis.

NAC Transcription Factors from Soybean (Glycine max L.) Differentially Regulated by Abiotic Stress

Plant-specific NAC (NAM, ATAF, and CUC)- domain proteins play important roles in plant development and stress responses. This study presents a comprehensive overview of GmSNAC genes. Eight of 71 GmSNAC genes differentially induced by abiotic stresses were identified. Based on the structural characteristics and phylogenetic relationships of Arabidopsis, rice, and soybean NACs, the GmSNACs were divided into five subgroups. Five GmSNAC proteins were localized in the nucleus and three GmSNAC proteins containing transmembrane domains were found in the nucleus and in other fractions. Based on the transcriptional activities of eight GmSNAC proteins fused to the GAL4 DB, it seems that the respective GmSNAC might play a transcriptional activator or repressor role in yeast. Here, we identify the roles of GmSNAC49 in stress responses and other processes. The overexpression of GmSNAC49 in Arabidopsis produced increased tolerance to drought stress compared to WT plants. Real-time (q)RT-PCR analyses suggest that overexpression of GmSNAC49 resulted in the upregulation of genes involved in the drought and/or ABA signaling pathway. These results suggest that GmSNAC49 might play a positive role in drought stress tolerance by regulating drought-responsive genes in Arabidopsis. Overall, the results of this systematic analysis of the GmSNAC family responsive to abiotic stress will provide novel tools and resources for the development of improved drought tolerant transgenic soybean cultivars.

SlNAC2 overexpression in Arabidopsis results in enhanced abiotic stress tolerance with alteration in glutathione metabolism.

Plant NAC (NAM, ATAF, and CUC) transcription factors (TF) have important roles to play in abiotic stress responses through activation of a battery of functional genes/transcriptional regulators responsible for stress tolerance. Here we report the cloning of a novel Solanum lycopersicum L., NAC2 TF having 960 nucleotides long CDS (GenBank: KT740994.1). Phylogenetic analysis depicted the similarity of SlNAC2 to other orthologs. SlNAC2 was overexpressed in Arabidopsis thaliana to assess and characterize its role in plant abiotic stress responses. The transgenic events were first confirmed by genomic DNA PCR and qRT PCR; then the T3 generation plants were used for stress assays. Soil stress assay depicted better survivability of the transgenic plants under both salt (NaCl) and drought (PEG) stress. The transgenic plants showed enhanced endurance; with better antioxidative response, reduced accumulation of reactive oxygen species (ROS) molecules and better retention of water in tissue. This study for the very first time analyzed the different stakeholders of the glutathione metabolism in SlNAC2 overexpressing transgenic lines on exposure to both salinity and PEG stress. The expression of the two genes (ɤ-ECS, GS) responsible for glutathione biosynthesis increased with SlNAC2 overexpression. Further glutathione reductase responsible for reduction of glutathione disulfide (GSSG) to glutathione (GSH) also increased significantly which suggested the regulation of glutathione metabolism as a mechanism for the osmotic stress tolerance conferred to plants upon NAC overexpression.

Targeted Mutagenesis of NAC Transcription Factor Gene, OsNAC041, Leading to Salt Sensitivity in Rice

Salinity is a major abiotic stress factor that seriously affects plant growth. Many genes are involved in the response to salt stress with various metabolism pathways. A number of plant transcription factor family genes have been found to be involved in the salt stress response, and NAM, ATAF and CUC (NAC) transcription factors are thought to act as active regulators during abiotic stress, especially salt stress. In this study, we detected a rice NAC transcription factor coding gene, OsNAC041, and confirmed that it influenced the germination of seeds under salt stress and salt tolerance of plants. OsNAC041 was primarily expressed in the leaves and located in the nucleus. Furthermore, the CRISPR/Cas9 method was used to obtain a targeted osnac041 mutant, of which the plant height was higher than that of the wild-type, showing increased salt sensitivity. Moreover, RNA-seq analysis revealed a number of differentially expressed genes (DEGs) involved in several important signaling pathways in the osnac041 mutant. Subsequently, Kyoto Encyclopedia of Genes and Genomes annotation also revealed differential expression of DEGs associated with mitogen-activated protein kinase signaling, peroxisome, eukaryotic- type ABC transporters, photosynthesis and plant hormones, which are involved in stress-related signaling pathways. Overall, our study suggested that OsNAC041 was involved in the salt stress response in rice. These findings not only provide empirical evidence of OsNAC041 function, but also provide new insight into its potential application in rice resistance breeding.

Genome-wide analysis of the NAC transcription factor family in Tartary buckwheat (Fagopyrum tataricum)

BackgroundThe NAC (NAM, ATAF1/2, and CUC2) transcription factor family represents a group of large plant-specific transcriptional regulators, participating in plant development and response to external stress. However, there is no comprehensive study on the NAC genes of Tartary buckwheat (Fagopyrum tataricum), a large group of extensively cultivated medicinal and edible plants. The recently published Tartary buckwheat genome permits us to explore all the FtNAC genes on a genome-wide basis.ResultsIn the present study, 80 NAC (FtNAC) genes of Tartary buckwheat were obtained and named uniformly according to their distribution on chromosomes. Phylogenetic analysis of NAC proteins in both Tartary buckwheat and Arabidopsis showed that the FtNAC proteins are widely distributed in 15 subgroups with one subgroup unclassified. Gene structure analysis found that multitudinous FtNAC genes contained three exons, indicating that the structural diversity in Tartary buckwheat NAC genes is relatively low. Some duplication genes of FtNAC have a conserved structure that was different from others, indicating that these genes may have a variety of functions. By observing gene expression, we found that FtNAC genes showed abundant differences in expression levels in various tissues and at different stages of fruit development.ConclusionsIn this research, 80 NAC genes were identified in Tartary buckwheat, and their phylogenetic relationships, gene structures, duplication, global expression and potential roles in Tartary buckwheat development were studied. Comprehensive analysis will be useful for a follow-up study of functional characteristics of FtNAC genes and for the development of high-quality Tartary buckwheat varieties.

A novel Miscanthus NAC transcription factor MlNAC10 enhances drought and salinity tolerance in transgenic Arabidopsis

NAC (NAM, ATAF1/2 and CUC2) proteins are key regulators of various plant stress tolerances. However, knowledge of NAC genes remains largely unknown in Miscanthus. Here, we characterized a novel NAC gene MlNAC10 from M. lutarioriparius than plays a role in abiotic stress tolerance. MlNAC10 encodes a nuclear-localized protein with a C-terminal transactivation domain, and has a specific binding affinity to the NAC recognition sequence (NACRS). Ectopic expression of MlNAC10 in Arabidopsis led to increased sensitivity to abscisic acid (ABA) at early seedling growth stages. In addition, the proline content was significantly increased and the reactive oxygen species (ROS) scavenging capability was significantly enhanced in MlNAC10 overexpression lines under ABA treatment. Moreover, the drought and salt stress tolerance was significantly improved in MlNAC10 overexpression lines. Consistently, the activities of three antioxidant enzymes, namely catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD), were dramatically stimulated in the overexpression lines compared to the wild type (WT). Correspondingly, the accumulation of ROS was dramatically decreased and malondialdehyde (MDA) was accumulated at a much lower level in the transgenic lines. Meanwhile, the expression of six abiotic stress-related genes was dramatically stimulated in the overexpression lines in comparison to the WT. Together, our results demonstrated that MlNAC10 acts as an important regulator of drought and salinity stress tolerance by stimulating antioxidant enzymes and alleviating ROS damage via the ABA signaling pathway.

Cloning, Characterization, and Expression Analysis of Eight Stress‐Related NAC Genes in Tartary Buckwheat

Plant‐specific NAC (NAM, ATAF1/2, and CUC2) transcription factors (TFs) play important roles in various stress responses. However, the characteristics and functions of NAC TFs in Tartary buckwheat [Fagopyrum tataricum (L.) Gaertn.], an important pseudocereal crop that is strongly adapted to growth in adverse environments, have not been investigated. Here, eight NAC‐like genes, termed FtNAC2 through FtNAC9, were isolated and characterized from Tartary buckwheat. Amino acid sequence alignment analysis demonstrated that all the FtNAC proteins contain typical NAM domain of the NAC TFs family in the N terminus. Phylogenetic analysis showed that the eight FtNAC TFs were assigned to three abiotic stress‐related functional subgroups. To investigate their roles in response to stresses, the relative expression levels of FtNAC genes were analyzed under abiotic stresses (salt, drought, cold, and ultraviolet B) and exogenous phytohormones (abscisic acid, methyl jasmonate, and salicylic acid) treatments. All the FtNAC genes responded to one or more treatments, among which FtNAC4 and FtNAC7 showed >20‐fold upregulation of messenger RNA levels in response to salt, drought, abscisic acid, and salicylic acid treatments. The expression analysis of the NAC gene family in Tartary buckwheat under abiotic stress open the way to further investigate the molecular mechanism of NAC‐dependent transcriptional control of stress response.