Project description:BackgroundNAC (NAM, ATAF1/2 and CUC2) domain proteins are plant-specific transcriptional factors known to play diverse roles in various plant developmental processes. NAC transcription factors comprise of a large gene family represented by more than 100 members in Arabidopsis, rice and soybean etc. Recently, a preliminary phylogenetic analysis was reported for NAC gene family from 11 plant species. However, no comprehensive study incorporating phylogeny, chromosomal location, gene structure, conserved motifs, and expression profiling analysis has been presented thus far for the model tree species Populus.ResultsIn the present study, a comprehensive analysis of NAC gene family in Populus was performed. A total of 163 full-length NAC genes were identified in Populus, and they were phylogenetically clustered into 18 distinct subfamilies. The gene structure and motif compositions were considerably conserved among the subfamilies. The distributions of 120 Populus NAC genes were non-random across the 19 linkage groups (LGs), and 87 genes (73%) were preferentially retained duplicates that located in both duplicated regions. The majority of NACs showed specific temporal and spatial expression patterns based on EST frequency and microarray data analyses. However, the expression patterns of a majority of duplicate genes were partially redundant, suggesting the occurrence of subfunctionalization during subsequent evolutionary process. Furthermore, quantitative real-time RT-PCR (RT-qPCR) was performed to confirm the tissue-specific expression patterns of 25 NAC genes.ConclusionBased on the genomic organizations, we can conclude that segmental duplications contribute significantly to the expansion of Populus NAC gene family. The comprehensive expression profiles analysis provides first insights into the functional divergence among members in NAC gene family. In addition, the high divergence rate of expression patterns after segmental duplications indicates that NAC genes in Populus are likewise to have been retained by substantial subfunctionalization. Taken together, our results presented here would be helpful in laying the foundation for functional characterization of NAC gene family and further gaining an understanding of the structure-function relationship between these family members.
Project description:Kiwifruit (Actinidia chinensis Planch) is suitable for neutral acid soil. However, soil salinization is increasing in kiwifruit production areas, which has adverse effects on the growth and development of plants, leading to declining yields and quality. Therefore, analyzing the salt tolerance regulation mechanism can provide a theoretical basis for the industrial application and germplasm improvement of kiwifruit. We identified 120 NAC members and divided them into 13 subfamilies according to phylogenetic analysis. Subsequently, we conducted a comprehensive and systematic analysis based on the conserved motifs, key amino acid residues in the NAC domain, expression patterns, and protein interaction network predictions and screened the candidate gene AvNAC030. In order to study its function, we adopted the method of heterologous expression in Arabidopsis. Compared with the control, the overexpression plants had higher osmotic adjustment ability and improved antioxidant defense mechanism. These results suggest that AvNAC030 plays a positive role in the salt tolerance regulation mechanism in kiwifruit.
Project description:Key messageWe found GmNAC06 plays an important role in salt stress responses through the phenotypic, physiological and molecular analyses of OE, VC, and Mutant composite soybean. Salinization affects 20% of all cultivated land worldwide because of the high salinity of irrigation water and the excessive use of water, and this amount is increasing daily. NAC (NAM, ATAF, and CUC) have been found to be involved in salt stress. In this study, a soybean NAC gene, GmNAC06 (Glyma06g21020.1), was cloned and functionally characterized. The results of expression analysis suggested that salt stress could influence the expression level of GmNAC06. The subcellular localization analysis results suggested that GmNAC06 may function as a transcription factor. Under salt stress, the overexpression technology combined with CRISPR-Cas9 system found that GmNAC06 could cause the accumulation of proline and glycine betaine to alleviate or avoid the negative effects of ROS; similarly, it could control the Na+/K+ ratios in hairy roots to maintain ionic homeostasis. The fresh weight of the transgenic hairy roots and the histochemical ROS staining of wild leaves suggested that transgenic hairy roots influence the function of wild leaves under salt stress conditions. Moreover, the expression levels of GmUBC2 and GmHKT1 were higher in the GmNAC06 hairy roots than in the control. Thus, the overexpression of GmNAC06 in hairy roots notably causes an entire composite plant to exhibit salt tolerance. The phenotype of composite soybean plants and transgenic Arabidopsis plants suggest that GmNAC06 plays a role in response to salt stress and could be useful in generating salt tolerant transgenic crops.
Project description:Plant growth is strictly controlled by cell division, elongation, and differentiation for which adequate supplies of intracellular ATP are required. However, it is unclear how changes in the amount of intracellular ATP affect cell division and growth. To reveal the specific pathway dependent on ATP concentration, we performed analyses on the Arabidopsis mitochondria mutation sd3. The mutant is tiny, a result of a low amount of ATP caused by the disruption of Tim21, a subunit of the TIM23 protein complex localized in the inner membrane of the mitochondria. Loss of function of suppressor of gamma response 1 (SOG1) also restored the dwarf phenotype of wild type treated with antimycin A, a blocker of ATP synthesis in mitochondria. The sd3 phenotype is partially restored by the introduction of sog1, suppressor of gamma response 1, and kin10/kin11, subunits of Snf1-related kinase 1 (SnRK1). Additionally, SOG1 interacted with SnRK1, and was modified by phosphorylation in planta only after treatment with antimycin A. Transcripts of several negative regulators of the endocycle were up-regulated in the sd3 mutant, and this high expression was not observed in sd3sog1 and sd3kin11. We suggest that there is a novel regulatory mechanism for the control of plant cell cycle involving SnRK1 and SOG1, which is induced by low amounts of intracellular ATP, and controls plant development.
Project description: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.
Project description:NAC (NAM, ATAF1,2, and CUC2) transcription factors are one of the largest transcription factor families found in the plants and are involved in diverse developmental and signalling events. Despite the availability of comprehensive genomic information from diverse plant species, the basic genomic, biochemical, and evolutionary details of NAC TFs have not been established. Therefore, NAC TFs family proteins from 160 plant species were analyzed in the current study. Study revealed, Brassica napus (410) encodes highest number and Klebsormidium flaccidum (3) encodes the lowest number of TFs. The study further revealed the presence of NAC TF in the Charophyte algae K. flaccidum. On average, the monocot plants encode higher number (141.20) of NAC TFs compared to the eudicots (125.04), gymnosperm (75), and bryophytes (22.66). Furthermore, our analysis revealed that several NAC TFs are membrane bound and contain monopartite, bipartite, and multipartite nuclear localization signals. NAC TFs were also found to encode several novel chimeric proteins and regulate a complex interactome network. In addition to the presence of NAC domain, several NAC proteins were found to encode other functional signature motifs as well. Relative expression analysis of NAC TFs in A. thaliana revealed root tissue treated with urea and ammonia showed higher level of expression and leaf tissues treated with urea showed lower level of expression. The synonymous codon usage is absent in the NAC TFs and it appears that they have evolved from orthologous ancestors and undergone vivid duplications to give rise to paralogous NAC TFs. The presence of novel chimeric NAC TFs are of particular interest and the presence of chimeric NAC domain with other functional signature motifs in the NAC TF might encode novel functional properties in the plants.
Project description:As like in mammalian system, the DNA damage responsive cell cycle checkpoint functions play crucial role for maintenance of genome stability in plants through repairing of damages in DNA and induction of programmed cell death or endoreduplication by extensive regulation of progression of cell cycle. ATM and ATR (ATAXIA-TELANGIECTASIA-MUTATED and -RAD3-RELATED) function as sensor kinases and play key role in the transmission of DNA damage signals to the downstream components of cell cycle regulatory network. The plant-specific NAC domain family transcription factor SOG1 (SUPPRESSOR OF GAMMA RESPONSE 1) plays crucial role in transducing signals from both ATM and ATR in presence of double strand breaks (DSBs) in the genome and found to play crucial role in the regulation of key genes involved in cell cycle progression, DNA damage repair, endoreduplication and programmed cell death. Here we report that Arabidopsis exposed to high salinity shows generation of oxidative stress induced DSBs along with the concomitant induction of endoreduplication, displaying increased cell size and DNA ploidy level without any change in chromosome number. These responses were significantly prominent in SOG1 overexpression line than wild-type Arabidopsis, while sog1 mutant lines showed much compromised induction of endoreduplication under salinity stress. We have found that both ATM-SOG1 and ATR-SOG1 pathways are involved in the salinity mediated induction of endoreduplication. SOG1was found to promote G2-M phase arrest in Arabidopsis under salinity stress by downregulating the expression of the key cell cycle regulators, including CDKB1;1, CDKB2;1, and CYCB1;1, while upregulating the expression of WEE1 kinase, CCS52A and E2Fa, which act as important regulators for induction of endoreduplication. Our results suggest that Arabidopsis undergoes endoreduplicative cycle in response to salinity induced DSBs, showcasing an adaptive response in plants under salinity stress.
Project description:The ARABIDOPSIS THALIANA ACTIVATION FACTOR 2 (ATAF2) protein has been demonstrated to be involved in various biological processes including biotic stress responses, photo morphogenesis, and auxin catabolism. However, the transcriptional function of ATAF2 currently remains elusive. Therefore, to further understand the molecular function of ATAF2, we evaluated the transcriptional activities of ATAF2 using a transient assay system in this study. We used an effector consisting of a GAL4-DNA binding domain (GAL4-BD) fused to ATAF2, and observed upregulated reporter gene expression, suggesting that ATAF2 potentially has transcriptional activation activity. ATAF2 has been shown to activate reporter gene expression under the control of the ORE1 promoter. By contrast, ATAF2 significantly repressed reporter gene expression driven by the NIT2 promoter. These data suggest that ATAF2 is a bifunctional transcription factor that can alter target gene expression depending on the promoter sequences.
Project description:The structure of the DNA-binding NAC domain of Arabidopsis ANAC (abscisic-acid-responsive NAC) has been determined by X-ray crystallography to 1.9A resolution (Protein Data Bank codes 1UT4 and 1UT7). This is the first structure determined for a member of the NAC family of plant-specific transcriptional regulators. NAC proteins are characterized by their conserved N-terminal NAC domains that can bind both DNA and other proteins. NAC proteins are involved in developmental processes, including formation of the shoot apical meristem, floral organs and lateral shoots, as well as in plant hormonal control and defence. The NAC domain does not possess a classical helix-turn-helix motif; instead it reveals a new transcription factor fold consisting of a twisted beta-sheet surrounded by a few helical elements. The functional dimer formed by the NAC domain was identified in the structure, which will serve as a structural template for understanding NAC protein function at the molecular level.
Project description:NAC proteins are one of the largest families of plant-specific transcription factors (TFs). They regulate diverse complex biological processes, including secondary xylem differentiation and wood formation. Recent genomic and transcriptomic studies of Tectona grandis L.f. (teak), one of the most valuable hardwood trees in the world, have allowed identification and analysis of developmental genes. In the present work, T. grandis NAC genes were identified and analyzed regarding to their evolution and expression profile during wood formation. We analyzed the recently published T. grandis genome, and identified 130 NAC proteins that are coded by 107 gene loci. These proteins were classified into 23 clades of the NAC family, together with Populus, Eucalyptus, and Arabidopsis. Data on transcript expression revealed specific temporal and spatial expression patterns for the majority of teak NAC genes. RT-PCR indicated expression of VND genes (Tg11g04450-VND2 and Tg15g08390-VND4) related to secondary cell wall formation in xylem vessels of 16-year-old juvenile trees. Our findings open a way to further understanding of NAC transcription factor genes in T. grandis wood biosynthesis, while they are potentially useful for future studies aiming to improve biomass and wood quality using biotechnological approaches.