NAC Transcription Factor Research Articles

High-transcriptional activation ability of bamboo SECONDARY WALL NAC transcription factors is derived from C-terminal domain.

The secondary cell wall, which is mainly composed of cellulose, hemicellulose, and lignin, constitutes woody tissues and gives physical strength and hydrophobic properties for resistance against environmental stresses. We cloned and functionally analyzed the homologous transcription factor (TF) genes of SECONDARY WALL NAC (SWN) proteins from Hachiku bamboo (Phyllostachys nigra; PnSWNs). An RT-PCR analysis showed that PnSWNs are expressed in young tissues in bamboo. Their transcriptional activation activities were higher than that of the Arabidopsis NAC SECONDARY WALL THICKENING PROMOTING FACTOR 3 (NST3) TF, which was equivalent to SWN TFs in monocot. PnSWNs preferred to activate the genes related to secondary cell wall formation but not the genes related to programmed cell death. When PnSWNs were expressed in Arabidopsis, they highly induced secondary cell wall formation, like previously-shown rice SWN1. Dissection analysis revealed that this high activity largely depends on C-terminal domain. These results demonstrate that the cloned bamboo SWNs function as regulators of secondary cell wall formation with strong activation ability derived from C-terminal domain, and could be served as new genetic tools for secondary cell wall manipulation.

Involvement of a novel NAP member LbNAP in flower senescence and dehydration stress in cut lily

In Arabidopsis thaliana, NAC-like and activated by AP3/PI (NAP) are NAC transcription factors that regulate leaf senescence and environment stress. Gene LbNAP, which has a typical NAC region, was cloned from lily petals. Our results indicated that LbNAP was located in the nucleus, and the gene had transcriptional activation activity. Further studies on LbNAP expression showed that it was lowest in green buds and highest in aging petals during bud development. Silencing of LbNAP in buds using virus-induced gene silencing resulted in a delayed senescence phenotype and less dehydration stress injury, which were related to the increase in catalase and superoxide dismutase activities and expression of their genes. Over-expression of LbNAP in A. thaliana (OE-LbNAP) resulted in slow root growth and decreased fresh weight. When treated with 250 mM mannitol, root length and fresh weight of transgenic seedlings were significantly lower than those of wild type. In addition, flowers of OE-LbNAP showed earlier senescence and weaker dehydration tolerance; when OE-LbNAP plants were subjected to 7 days of drought stress, their survival rate was significantly lower than that of the wild type. These results suggest that LbNAP was positively involved in age-induced flower senescence and dehydration stress.

The transcription factor SlNAP1 increases salt tolerance by modulating ion homeostasis and ROS metabolism in Solanum lycopersicum

NAC transcription factors (TFs) play an important role in the plant resistant response to biotic and abiotic stresses. However, the functions of the most NAC TFs are still unknown, especially in tomato. Here, we identified and functionally characterized an NAC TFs, SlNAP1, in tomato, and found that SlNAP1 was significantly induced by salt stress. Under 150 mM NaCl treatments, morphological indexes of SlNAP1 over-expressed (SlNAP1-OE) transgenic tomato lines were significantly better than the wild-type (WT) plants. The content of Na+ in leaves and roots of SlNAP1-OE transgenic plants decreased, while the K+ content in leaves, roots, and stems increased compared with WT plants. The expression of the salt stress-related genes (NHX1, HKT1;2 and SOS1) in SlNAP1-OE plants were also significantly up-regulated under salt stress. The SOD, POD and CAT activities and the expression level of antioxidant oxidase synthesis genes of SlNAP1-OE lines were significantly increased. In addition, the SlNAP1-OE lines accumulated less MDA, H2O2 and O2•−, improved antioxidant defense systems which contributed to increase salt tolerance. In summary, our data suggest that SlNAP1 positively regulates salt tolerance in tomato by regulating ion homeostasis and ROS metabolism.

Comprehensive analysis of pathogen-responsive wheat NAC transcription factors: new candidates for crop improvement.

Wheat NAC (TaNAC) transcription factors are important regulators of stress responses and developmental processes. This study proposes a new TaNAC nomenclature and identified defense-associated TaNACs based on the analysis of RNA-sequencing datasets of wheat tissue infected with major fungal pathogens. A total of 146 TaNACs were pathogen-responsive, of which 52 were orthologous with functionally characterized defense-associated NACs from barley, rice, and Arabidopsis, as deduced via phylogenetic analysis. Next, we focused on the phylogenetic relationship of the pathogen-responsive TaNACs and their expression profiles in healthy and diseased tissues. Three subfamilies ("a," "e," and "f") were significantly enriched in pathogen-responsive TaNACs, of which the majority were responsive to at least 2 pathogens (universal pathogen response). Uncharacterized TaNACs from subfamily "a" enriched with defense-associated NACs are promising candidates for functional characterization in pathogen defense. In general, pathogen-responsive TaNACs were expressed in at least 2 healthy organs. Lastly, we showed that the wheat NAM domain is significantly divergent in sequence in subfamilies "f," "g," and "h" based on HMMER and motif analysis. New protein motifs were identified in both the N- and C-terminal parts of TaNACs. Three of those identified in the C-terminal part were linked to pathogen responsiveness of the TaNACs and 2 were linked to expression in grain tissue. Future studies should benefit from this comprehensive in silico analysis of pathogen-responsive TaNACs as a basis for selecting the most promising candidates for functional validation and crop improvement.

FtNAC31, a Tartary buckwheat NAC transcription factor, enhances salt and drought tolerance in transgenic Arabidopsis

Tartary buckwheat [Fagopyrum tataricum (L.) Gaertn.] is a pseudocereal with strongly abiotic resistance. NACs, one of the largest plant-specific transcription factors (TFs), are involved in various stress responses. However, the characteristics and regulatory mechanisms of NAC TFs remain unclarified clearly in Tartary buckwheat (TB). In this study, it validated that salt, drought, and abscisic acid (ABA) stress significantly up-regulated the expression of NAC TF gene FtNAC31. Its coding protein has a C-terminal transactivated domain and localized in the nucleus, suggesting that FtNAC31 might play a transcriptional activation role in TB. Notably, overexpression of FtNAC31 lowered the seed germination rate upon ABA treatment and enhanced the tolerance to salt and drought stress in transgenetic Arabidopsis. Furthermore, under various stresses, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in FtNAC31 overexpressed lines exhibited a sharp increase trend. Meanwhile, the expression levels of several stress-associated genes including RD29A, RD29B, RD22, DREB2B, NCED3, and POD1, were dramatically upregulated in lines overexpressing FtNAC31. Altogether, overproduction of FtNAC31 could enhance the resistance to salt and drought stresses in transgenic Arabidopsis, which most likely functioned in an ABA-dependent way.

Comparative Transcriptome Analysis and Genetic Methods Revealed the Biocontrol Mechanism of Paenibacilluspolymyxa NSY50 against Tomato Fusarium Wilt.

Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici (Fol) is a common disease that affects tomatoes, which can cause the whole plant to wilt and seriously reduce the production of tomatoes in greenhouses. In this study, the morphological indexes, photosynthetic performance and incidence rate of NSY50 under Fol infection were evaluated. It was found that NSY50 could improve the growth of tomato seedlings and significantly reduce the incidence rate of Fusarium wilt. However, the molecular mechanism of NSY50 that induces resistance to Fusarium wilt is still unclear. We used transcriptomic methods to analyze NSY50-induced resistance to Fol in tomatoes. The results showed that plant defense related genes, such as PR and PAL, were highly expressed in tomato seedlings pretreated with NSY50. At the same time, photosynthetic efficiency, sucrose metabolism, alkaloid biosynthesis and terpene biosynthesis were significantly improved, which played a positive role in reducing the damage caused by Fol infection and enhancing the disease tolerance of seedlings. Through transgenic validation, we identified an important tomato NAC transcription factor, SlNAP1, which was preliminarily confirmed to be effective in relieving the detrimental symptoms induced by Fol. Our findings reveal that P. polymyxa NSY50 is an effective plant-growth-promoting rhizosphere bacterium and also a biocontrol agent of soil-borne diseases, which can significantly improve the resistance of tomato to Fusarium wilt.

Comparative genomic analysis and phylogeny of NAC25 gene from cultivated and wild Coffea species.

Coffee is a high value agricultural commodity grown in about 80 countries. Sustainable coffee cultivation is hampered by multiple biotic and abiotic stress conditions predominantly driven by climate change. The NAC proteins are plants specific transcription factors associated with various physiological functions in plants which include cell division, secondary wall formation, formation of shoot apical meristem, leaf senescence, flowering embryo and seed development. Besides, they are also involved in biotic and abiotic stress regulation. Due to their ubiquitous influence, studies on NAC transcription factors have gained momentum in different crop plant species. In the present study, NAC25 like transcription factor was isolated and characterized from two cultivated coffee species, Coffea arabica and Coffea canephora and five Indian wild coffee species for the first time. The full-length NAC25 gene varied from 2,456 bp in Coffea jenkinsii to 2,493 bp in C. arabica. In all the seven coffee species, sequencing of the NAC25 gene revealed 3 exons and 2 introns. The NAC25 gene is characterized by a highly conserved 377 bp NAM domain (N-terminus) and a highly variable C terminus region. The sequence analysis revealed an average of one SNP per every 40.92 bp in the coding region and 37.7 bp in the intronic region. Further, the non-synonymous SNPs are 8-11 fold higher compared to synonymous SNPs in the non-coding and coding region of the NAC25 gene, respectively. The expression of NAC25 gene was studied in six different tissue types in C. canephora and higher expression levels were observed in leaf and flower tissues. Further, the relative expression of NAC25 in comparison with the GAPDH gene revealed four folds and eight folds increase in expression levels in green fruit and ripen fruit, respectively. The evolutionary relationship revealed the independent evolution of the NAC25 gene in coffee.

Overexpression of cotton GhNAC072 gene enhances drought and salt stress tolerance in transgenic Arabidopsis

BackgroundCrops face several environmental stresses (biotic and abiotic), thus resulting in severe yield losses. Around the globe abiotic stresses are the main contributors of plant damages, primarily drought and salinity. Many genes and transcription factors are involved in abiotic and biotic stress responses. NAC TF (Transcription Factors) improves tolerance to stresses by controlling the physiological and enzyme activities of crops.ResultsIn current research, GhNAC072 a highly upregulated TF in RNA-Seq was identified as a hub gene in the co-expression network analysis (WGCNA). This gene was transformed to Arabidopsis thaliana to confirm its potential role in drought and salt stress tolerance. Significant variations were observed in the morpho-physiological traits with high relative leaf water contents, chlorophyll contents, higher germination and longer root lengths of the overexpressed lines and low excised leaf loss and ion leakage as compared to the wildtype plants. Besides, overexpressed lines have higher amounts of antioxidants and low oxidant enzyme activities than the wildtype during the period of stress exposure.ConclusionsIn summary, the above analysis showed that GhNAC072 might be the true candidate involved in boosting tolerance mechanisms under drought and salinity stress.

At-ore1 Gene Induces Distinct Novel H2O2-NACs Signaling in Regulating the Leaf Senescence in Soybeans (Glycine max L.)

Senescence is modulated by ORESARA1 (ORE1), a NAC transcription factor that interacts with hormones to fully induce senescence. The At-ore1 gene acts as a suppressor of leaf senescence; however, its exact role in this respect has not been clearly defined. In this study, the function of At-ore1 during leaf senescence was analyzed in soybeans. The precocious leaf senescence of the ore1-1 line was associated with greater chlorophyll loss, leaf necrosis, and redox imbalance in the early vegetative stage during the hyper-accumulation of endogenous abscisic acid (ABA) by enhancing the expression of GmNECD3-related ABA synthesis. At-ore1 induced ABA regulation of the H2O2-GmARF2-GmNAC081 signaling circuit, which relays the At-ore1-induced cell death signal mediation to the caspase-1-like vacuolar processing enzyme (VPE) expression, triggering programmed cell death. In contrast, it was found that At-ore1 functions in IAA to delay leaf-senescence-mediated suppression of the expression of ABA, ROS, and senescence-associated gene 39 (GmSAG39). The IAA-induced GmNAC065 expression controls soybean leaves’ longevity, as discovered by screening At-ore1 expression in ore1-6 for a more stay-green leaf phenotype by helping to increase seed yields. These results uncover a mechanism that modulates ore1 plants’ amplitude expression involved in the ABA/IAA balance in the activation of GmNAC081- or GmNAC065-dependent H2O2 levels, which are crucial in the senescence or delayed leaf senescence of soybeans.

Ectopic Expression of AeNAC83, a NAC Transcription Factor from Abelmoschus esculentus, Inhibits Growth and Confers Tolerance to Salt Stress in Arabidopsis.

NAC transcription factors play crucial roles in plant growth, development and stress responses. Previously, we preliminarily identified that the transcription factor AeNAC83 gene was significantly up-regulated under salt stress in okra (Abelmoschus esculentus). Herein, we cloned the nuclear-localized AeNAC83 from okra and identified its possible role in salt stress response and plant growth. The down-regulation of AeNAC83 caused by virus-induced gene silencing enhanced plant sensitivity to salt stress and increased the biomass accumulation of okra seedlings. Meanwhile, AeNAC83-overexpression Arabidopsis lines improved salt tolerance and exhibited many altered phenotypes, including small rosette, short primary roots, and promoted crown roots and root hairs. RNA-seq showed numerous genes at the transcriptional level that changed significantly in the AeNAC83-overexpression transgenic and the wild Arabidopsis with or without NaCl treatment, respectively. The expression of most phenylpropanoid and flavonoid biosynthesis-related genes was largely induced by salt stress. While genes encoding key proteins involved in photosynthesis were almost declined dramatically in AeNAC83-overexpression transgenic plants, and NaCl treatment further resulted in the down-regulation of these genes. Furthermore, DEGs encoding various plant hormone signal pathways were also identified. These results indicate that AeNAC83 is involved in resistance to salt stress and plant growth.

The Regulation of Xylem Development by Transcription Factors and Their Upstream MicroRNAs.

Xylem, as a unique organizational structure of vascular plants, bears water transport and supports functions necessary for plant survival. Notably, secondary xylem in the stem (i.e., wood) also has important economic and ecological value. In view of this, the regulation of xylem development has been widely concerned. In recent years, studies on model plants Arabidopsis and poplar have shown that transcription factors play important regulatory roles in various processes of xylem development, including the directional differentiation of procambium and cambium into xylem, xylem arrangement patterns, secondary cell wall formation and programmed cell death. This review focuses on the regulatory roles of widely and thoroughly studied HD-ZIP, MYB and NAC transcription factor gene families in xylem development, and it also pays attention to the regulation of their upstream microRNAs. In addition, the existing questions in the research and future research directions are prospected.

The colonization of land was a likely driving force for the evolution of mitochondrial retrograde signalling in plants.

Most retrograde signalling research in plants was performed using Arabidopsis, so an evolutionary perspective on mitochondrial retrograde regulation (MRR) is largely missing. Here, we used phylogenetics to track the evolutionary origins of factors involved in plant MRR. In all cases, the gene families can be traced to ancestral green algae or earlier. However, the specific subfamilies containing factors involved in plant MRR in many cases arose during the transition to land. NAC transcription factors with C-terminal transmembrane domains, as observed in the key regulator ANAC017, can first be observed in non-vascular mosses, and close homologs to ANAC017 can be found in seed plants. Cyclin-dependent kinases (CDKs) are common to eukaryotes, but E-type CDKs that control MRR also diverged in conjunction with plant colonization of land. AtWRKY15 can be traced to the earliest land plants, while AtWRKY40 only arose in angiosperms and AtWRKY63 even more recently in Brassicaceae. Apetala 2 (AP2) transcription factors are traceable to algae, but the ABI4 type again only appeared in seed plants. This strongly suggests that the transition to land was a major driver for developing plant MRR pathways, while additional fine-tuning events have appeared in seed plants or later. Finally, we discuss how MRR may have contributed to meeting the specific challenges that early land plants faced during terrestrialization.

Identification and Analysis of MADS-box, WRKY, NAC, and SBP-box Transcription Factor Families in Diospyros oleifera Cheng and Their Associations with Sex Differentiation

Transcription factors are crucial for plant growth and development. MADS-box, WRKY, NAC, and SBP-box, some of the most vital transcription factors, are not well identified in Diospyros spp., and their floral development and sex differentiation related functions remain unknown. We identified and analysed 53 MADS-box, 66 WRKY, 83 NAC, and 17 SBP-box transcription factors using the chromosomal D. oleifera genome. There were six DolSBPs identified as miR156 and miR157 targets. According to the multiple sequence alignments of Arabidopsis and D. oleifera proteins and their conserved domains and motifs, DolMADSs were divided into 23 type I and 30 type II. The DolWRKYs, DolNACs, and DolSBPs were divided into 7, 16, and 6 subgroups, respectively. It was found that one DolMADS, five DolWRKYs, one DolNAC, and four DolSBPs may promote unisexual female flowers development, while three DolMADSs, four DolWRKYs, and one DolNAC may enhance unisexual male flowers development. The functions among the different members of the same family may, thus, vary widely. The results will help to elucidate the evolution of the MADS-box, WRKY, NAC, and SBP-box genes families in D. oleifera and to determine their functions in flower development for Diospyros spp.

Profiling of transcriptional regulators associated with starch biosynthesis in sorghum (Sorghum bicolor L.)

Starch presents as the major component of grain endosperm of sorghum (Sorghum bicolor L.) and other cereals, serving as the main energy supplier for both plants and animals, as well as important industrial raw materials of human beings, and was intensively concerned world widely. However, few documents focused on the pathway and transcriptional regulations of starch biosynthesis in sorghum. Here we presented the RNA-sequencing profiles of 20 sorghum tissues at different developmental stages to dissect key genes associated with sorghum starch biosynthesis and potential transcriptional regulations. A total of 1,708 highly expressed genes were detected, namely, 416 in grains, 736 in inflorescence, 73 in the stalk, 215 in the root, and 268 genes in the leaf. Besides, 27 genes encoded key enzymes associated with starch biosynthesis in sorghum were identified, namely, six for ADP-glucose pyrophosphorylase (AGPase), 10 for starch synthases (SSs), four for both starch-branching enzymes (SBE) and starch-debranching enzymes (DBEs), two for starch phosphorylases (SPs), and one for Brittle-1 (BT1). In addition, 65 transcription factors (TFs) that are highly expressed in endosperm were detected to co-express with 16 out of 27 genes, and 90 cis-elements were possessed by all 27 identified genes. Four NAC TFs were cloned, and the further assay results showed that three of them could in vitro bind to the CACGCAA motif within the promoters of SbBt1 and SbGBSSI, two key genes associated with starch biosynthesis in sorghum, functioning in similar ways that reported in other cereals. These results confirmed that sorghum starch biosynthesis might share the same or similar transcriptional regulations documented in other cereals, and provided informative references for further regulatory mechanism dissection of TFs involved in starch biosynthesis in sorghum.

Genome-wide identification and comprehensive analyses of NAC transcription factor gene family and expression analysis under Fusarium kyushuense and drought stress conditions in Passiflora edulis.

The NAC gene family is one of the largest plant transcription factors (TFs) families and plays important roles in plant growth, development, metabolism, and biotic and abiotic stresses. However, NAC gene family has not been reported in passion fruit (Passiflora edulis). In this study, a total of 105 NAC genes were identified in the passion fruit genome and were unevenly distributed across all nine-passion fruit chromomere, with a maximum of 48 PeNAC genes on chromosome one. The physicochemical features of all 105 PeNAC genes varied including 120 to 3,052 amino acids, 3 to 8 conserved motifs, and 1 to 3 introns. The PeNAC genes were named (PeNAC001–PeNAC105) according to their chromosomal locations and phylogenetically grouped into 15 clades (NAC-a to NAC-o). Most PeNAC proteins were predicted to be localized in the nucleus. The cis-element analysis indicated the possible roles of PeNAC genes in plant growth, development, light, hormones, and stress responsiveness. Moreover, the PeNAC gene duplications including tandem (11 gene pairs) and segmental (12 gene pairs) were identified and subjected to purifying selection. All PeNAC proteins exhibited similar 3D structures, and a protein–protein interaction network analysis with known Arabidopsis proteins was predicted. Furthermore, 17 putative ped-miRNAs were identified to target 25 PeNAC genes. Potential TFs including ERF, BBR-BPC, Dof, and bZIP were identified in promoter region of all 105 PeNAC genes and visualized in a TF regulatory network. GO and KEGG annotation analysis exposed that PeNAC genes were related to different biological, molecular, and cellular terms. The qRT-PCR expression analysis discovered that most of the PeNAC genes including PeNAC001, PeNAC003, PeNAC008, PeNAC028, PeNAC033, PeNAC058, PeNAC063, and PeNAC077 were significantly upregulated under Fusarium kyushuense and drought stress conditions compared to controls. In conclusion, these findings lay the foundation for further functional studies of PeNAC genes to facilitate the genetic improvement of plants to stress resistance.

Inducible expression of truncated NAC62 provides tolerance against Alternaria brassicicola and imparts developmental changes in Indian mustard

Indian mustard (Brassica juncea) faces significant yield loss due to the ‘Black Spot Disease,’ caused by a fungus Alternaria brassicicola. In plants, NAC transcription factors (NAC TFs) are known for their roles in development and stress tolerance. One such NAC TF, NAC 62, was induced during A. brassicicola challenge in Sinapis alba, a non-host resistant plant against this fungus. Sequence analyses of BjuNAC62 from B. juncea showed that it belonged to the membrane-bound class of transcription factors. Gene expression study revealed differential protein processing of NAC62 between B. juncea and S. alba on pathogen challenge. Furthermore, NAC62 processing to 25 kDa protein was found to be unique to the resistant plant during pathogenesis. Conditional expression of BjuNAC62ΔC, which lacks its transmembrane domain, in B. juncea showed improved tolerance to A. brassicicola. BjuNAC62ΔC processing to 25 kDa product was also observed in tolerant transgenic plants. Additionally, transgenic plants showed induced expression of genes associated with defense-related phytohormone signaling pathways on pathogen challenge. Again, altered phenotypes suggest a possible developmental effect of BjuNAC62∆C in transgenic plants. The overall results suggest that the processing of BjuNAC62 might be playing a crucial role in resistance response against Black Spot disease by modulating defense-associated genes.

Comprehensive transcriptomic and metabolomic analysis revealed distinct flavonoid biosynthesis regulation during abnormal pistil development in Japanese apricot

Japanese apricot is an imperative stone fruit plant with numerous processing importance. The failure of reproductive system is the most common cause of fruit loss, through which pistil abortion is the fundamental one. To understand this mechanism, we used a combination of transcriptomic and metabolomic approaches to investigate the biochemical and molecular basis of flavonoid biosynthesis. Due to the regulated expression of flavonoid pathway-related genes in plants, flavonoid biosynthesis is largely regulated at the transcriptional level. A total of 2272 differently expressed genes and 215 differential metabolites were found. The expression of the genes and metabolites encoding flavonoid biosynthesis was lower in abnormal pistils that are in line with the flavonoid quantification from abnormal pistils. Besides, a couple of genes were also detected related to MYB, MADS, NAC and bHLH transcription factors. Remarkably, we found ‘hydroxycinnamoyl transferase (LOC103323133)’ and flavonoid related metabolite ‘2-hydroxycinnamic acid’ was lower expressed in abnormal pistil, proposing the cause of pistil abortion. Collectively, the present study delivers inclusive transcriptional and metabolic datasets that proposed valuable prospects to unravel the genetic mechanism underlying pistil abortion.

Analysis of Floral Organ Development and Sex Determination in Schisandra chinensis by Scanning Electron Microscopy and RNA-Sequencing.

S. chinensis is a typical monoecious plant, and the number and development of female flowers determines the yield of S. chinensis. Due to a lack of genetic information, the molecular mechanism of sex differentiation in S. chinensis remains unclear. In this study, the combination of scanning electron microscopy (SEM) and RNA sequencing (RNA-seq) was used to understand the way of sex differentiation of S. chinensis and to mine the related genes of sex determination. The result shows the development of male and female S. chinensis flowers was completed at the same time, the unisexual S. chinensis flowers did not undergo a transition stage between sexes, and sex may have been determined at an early stage in flower development. The results of the gene function analysis of the plant hormone signaling pathway and sucrose metabolism pathway suggest that auxin and JA could be the key hormones for sex differentiation in S. chinensis, and sucrose may promote pollen maturation at the later stage of male flower development. Two AGAMOUS (GAG) genes, 10 AGAMOUS-like MADS-box (AGLs) genes, and the MYB, NAC, WRKY, bHLH, and Trihelix transcription factor families may play important roles in sex determination in S. chinensis. Taken together, the present findings provide valuable genetic information on flower development and sex determination in S. chinensis.

Drought resistance of tobacco overexpressing the AfNAC1 gene of Amorpha fruticosa Linn.

Plants are often adversely affected by abiotic stresses such as drought, low temperature, and salinity during growth, and plant NAC-like transcription factors are involved in regulating growth and developmental processes in response to stresses such as drought and salinity. In this study, to investigate the function of AfNAC1, a co-expression network of AfNAC1 genes was constructed using gene expression data from the Chinese legume deciduous shrub, Amorpha fruticosa Linn. A 576 bp NAC transcription factor (AfNAC1 gene, MN180266) encoding 191 amino acids was isolated from Amorpha fruticosa seedlings by RT-PCR. qRT-PCR showed that the AfNAC1 gene was expressed in the roots, stems, leaves, and flowers of Amorpha fruticosa. However, drought stress significantly increased root expression, and the AfNAC1 protein was localized in the nucleus by green fluorescence detection. This study analyzed the drought resistance of overexpressing tobacco in depth. Under natural drought stress, the chlorophyll and antioxidant enzyme activities of overexpressing plants were significantly higher than those of wild-type (WT) plants, but the MDA content was lower than that of WT; after rehydration the Fv/Fm values of AfNAC1-overexpressing tobacco recovered faster than those of wild-type tobacco and rapidly reached the control levels; AfNAC1 may be involved in the regulation of the photosystem and indirectly in the regulation of the plant in response to drought stress.

Genome-Wide Analysis of the NAC Family Associated with Two Paleohexaploidization Events in the Tomato.

NAC transcription factors play an important regulatory role in tomato fruit ripening. We chose a novel perspective to explore the traces left by two paleopolyploidizations in the NAC family using a bioinformatics approach. We found that 85 (S. lycopersicum) and 88 (S. pennellii) members of the NAC family were present in two tomatoes, and most of them were amplified from two paleohexaploidizations. We differentiated NAC family members from the different paleohexaploidizations and found that the SWGT-derived NAC genes had more rearrangement events, so it was different from the DWGT-derived NAC genes in terms of physicochemical properties, phylogeny, and gene location. The results of selection pressure show that DWGT-derived NAC genes tended to be positively selected in S. lycopersicum and negatively selected in S. pennellii. A comprehensive analysis of paleopolyploidization and expression reveals that DWGT-derived NAC genes tend to promote fruit ripening, and are expressed at the early and middle stages, whereas SWGT-derived NAC genes tend to terminate fruit growth and are expressed at the late stages of fruit ripening. This study obtained NAC genes from different sources that can be used as materials for tomato fruit development, and the method in the study can be extended to the study of other plants.