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孝顺竹笋箨全长转录组测序分析
Full-length transcriptome sequencing and annotation analyses of Bambusa multiplex sheath
【目的】揭示竹子笋箨的生物学功能与其衰老的分子基础。【方法】利用PacBio Sequel 3代全长转录组测序技术结合生物信息学方法,对孝顺竹不同衰老阶段笋箨全长转录本进行分析。【结果】共获得106 148 条平均长度为3 615 bp的全长转录本。多数转录本长度分布在1.4~7.0 kb。NCBI等注释显示,97.34%的转录本具有注释结果。Mercator注释分析显示笋箨转录本覆盖了其全部34 个类别,其中与蛋白类别相关的序列最多,达到了18 224 条;与microRNA类别相关的最少,仅有9 条。在重要功能基因方面,共获得了2 489 条激素代谢及信号转导相关序列; 8 804 条转录因子序列中393 条与光合作用相关的转录本。其中,注释到的189 条共30 类NAC(NAM/ATAF/CUC)转录因子基因,93.33%的NAC基因,共计28类,其表达量与笋箨衰老呈相关性, 包括已被证实在叶片衰老中具有重要调控作用的NAC002、NAC016、NAC017、NAC029(NAP)、NAC042、NAC055与NAC083等7个NAC转录因子与NAC014等14个被报道在叶片衰老中具有潜在作用的NAC基因。NAC025、NAC028、NAC045、NAC061、NAC086、NAC103与NAC1L (NAC 1 Like) 7 个NAC转录因子表达与孝顺竹笋箨衰老呈正相关,为新发现的正调控笋箨衰老的潜在转录因子。此外,利用MISA程序在76 499 个序列中检测到简单序列重复(simple sequence repeats,SSR)位点,主要以单核苷酸重复(SSRs)为主,占据了全部(SSRs)的55.2%。利用PLEK等软件共获得2 769个长链非编码RNA(long non-coding RNA, lncRNA)。【结论】竹子笋箨基因表达多样化,并具有完整的光合系统基因,显示其具有潜在光合功能;NAC转录因子在孝顺竹笋箨衰老中具有潜在重要调控作用。本研究首次解析了竹子笋箨的全长转录本特征,为今后深入分析竹子笋箨功能及其衰老的分子机制奠定基础。
【Objective】Currently, few reports have described the biological function of the bamboo sheath. This work aimed to elucidate the possible functions and the underlying biological mechanisms of the bamboo sheath from the perspective of molecular biology.【Method】Using PacBio Sequel full-length sequencing technology, we analyzed the transcriptomic profile of the culm sheath at different senescence stages of Bambusa multiplex.【Result】A total of 106 148 transcripts with an average length of 3 615 base pairs (bp) were obtained. Of those transcripts, 97.34% had annotated results. Mercator annotation further revealed that the transcripts covered all 34 functional subgroups associated with the bamboo sheath. The protein subgroup contained the most transcripts, with 18 224 transcripts. While the microRNA subgroup contained the least transcripts, with only nine being present in this subgroup. Additionally, 2 489 hormone-related transcripts and 8 804 transcription factors were detected. Interestingly, 393 transcripts related to photosynthesis were discovered in the full-length transcriptome of the B. multiplex sheath. A total of 189 transcripts encoding 30 NAC transcription factor genes were also identified. The expression of 93.33% of NAC transcription factor genes was found to be positively or negatively correlated with sheath senescence. Of them, seven NACs, including NAC002, NAC016, NAC017, NAC029(NAP), NAC042, NAC055 and NAC083 have been reported to play important roles in regulating leaf senescence; 14 NACs, including NAC014, have been reported to have potential roles in leaf senescence; and seven bamboo sheath senescence-associated NACs, including NAC025, NAC028, NAC045, NAC061, NAC086, NAC103 and NAC1L were newly discovered. The MISA software analysis revealed that 76 499 transcripts contain simple sequence repeats (SSRs). Most are single nucleotide repeat SSRs, accounting for 55.2% of all discovered SSRs. Additionally, 2 769 long non-coding RNAs (lncRNAs) were detected by using software such as PLRK et al.【Conclusion】These results revealed that various genes are actively expressed in the bamboo sheath. A number of transcripts related to all aspects of photosynthesis were detected in the bamboo sheath, indicating that the bamboo sheath may have the photosynthetic capacity. The majority of the identified NACs was associated with leaf senescence, suggesting a potential role of NACs in bamboo sheath senescence. Taken together, our work provides the first insights into the transcriptomic features of the bamboo sheath and provides a foundation for future studies to reveal the biological function of the bamboo sheath and the underlying molecular mechanisms of bamboo sheath senescence.
孝顺竹 / PacBio / 简单序列重复(SSR) / lncRNA / NAC / 衰老
Bambusa multiplex / PacBio / simple sequence repeats(SSR) / lncRNA / NAC / senescence
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The primary thickening growth of Moso (Phyllostachys edulis) underground shoots largely determines the culm circumference. However, its developmental mechanisms remain largely unknown. Using an integrated anatomy, mathematics and genomics approach, we systematically studied cellular and molecular mechanisms underlying the growth of Moso underground shoots. We discovered that the growth displayed a spiral pattern and pith played an important role in promoting the primary thickening process of Moso underground shoots and driving the evolution of culms with different sizes among different bamboo species. Different with model plants, the shoot apical meristem (SAM) of Moso is composed of six layers of cells. Comparative transcriptome analysis identified a large number of genes related to the vascular tissue formation that were significantly upregulated in a thick wall variant with narrow pith cavity, mildly spiral growth, and flat and enlarged SAM, including those related to plant hormones and those involved in cell wall development. These results provide a systematic perspective on the primary thickening growth of Moso underground shoots, and support a plausible mechanism resulting in the narrow pith cavity, weak spiral growth but increased vascular bundle of the thick wall Moso.
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Background: Gene fusions derive from chromosomal rearrangements. The resulting chimeric transcripts are often endowed with oncogenic potential. Furthermore, they serve as diagnostic tools for the clinical classification of cancer subgroups with different prognosis and, in some cases, they can provide specific drug targets. To date, many efforts have been carried out to study gene fusion events occurring in tumor samples. In recent years, the availability of a comprehensive next-generation sequencing dataset for all existing human tumor cell lines has provided the opportunity to further investigate these data in order to identify novel and still uncharacterized gene fusion events. Results: In our work, we have extensively reanalyzed 935 paired-end RNA-sequencing experiments downloaded from the Cancer Cell Line Encyclopedia repository, aiming at addressing novel putative cell-line specific gene fusion events in human malignancies. The bioinformatics analysis has been performed by the execution of four gene fusion detection algorithms. The results have been further prioritized by running a Bayesian classifier that makes an in silico validation. The collection of fusion events supported by all of the predictive software results in a robust set of approximately 1,700 in silico predicted novel candidates suitable for downstream analyses. Given the huge amount of data and information produced, computational results have been systematized in a database named LiGeA. The database can be browsed through a dynamic and interactive web portal, further integrated with validated data from other well-known repositories. Taking advantage of the intuitive query forms, the users can easily access, navigate, filter, and select the putative gene fusions for further validations and studies. They can also find suitable experimental models for a given fusion of interest. Conclusions: We believe that the LiGeA resource can represent not only the first compendium of both known and putative novel gene fusion events in the catalog of all of the human malignant cell lines but it can also become a handy starting point for wet-lab biologists who wish to investigate novel cancer biomarkers and specific drug targets.
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Moso bamboo (Phyllostachys edulis) represents one of the fastest-spreading plants in the world, due in part to its well-developed rhizome system. However, the post-transcriptional mechanism for the development of the rhizome system in bamboo has not been comprehensively studied. We therefore used a combination of single-molecule long-read sequencing technology and polyadenylation site sequencing (PAS-seq) to re-annotate the bamboo genome, and identify genome-wide alternative splicing (AS) and alternative polyadenylation (APA) in the rhizome system. In total, 145 522 mapped full-length non-chimeric (FLNC) reads were analyzed, resulting in the correction of 2241 mis-annotated genes and the identification of 8091 previously unannotated loci. Notably, more than 42 280 distinct splicing isoforms were derived from 128 667 intron-containing full-length FLNC reads, including a large number of AS events associated with rhizome systems. In addition, we characterized 25 069 polyadenylation sites from 11 450 genes, 6311 of which have APA sites. Further analysis of intronic polyadenylation revealed that LTR/Gypsy and LTR/Copia were two major transposable elements within the intronic polyadenylation region. Furthermore, this study provided a quantitative atlas of poly(A) usage. Several hundred differential poly(A) sites in the rhizome-root system were identified. Taken together, these results suggest that post-transcriptional regulation may potentially have a vital role in the underground rhizome-root system.
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MAPMAN is a user-driven tool that displays large data sets onto diagrams of metabolic pathways or other processes. SCAVENGER modules assign the measured parameters to hierarchical categories (formed 'BINs', 'subBINs'). A first build of TRANSCRIPTSCAVENGER groups genes on the Arabidopsis Affymetrix 22K array into >200 hierarchical categories, providing a breakdown of central metabolism (for several pathways, down to the single enzyme level), and an overview of secondary metabolism and cellular processes. METABOLITESCAVENGER groups hundreds of metabolites into pathways or groups of structurally related compounds. An IMAGEANNOTATOR module uses these groupings to organise and display experimental data sets onto diagrams of the users' choice. A modular structure allows users to edit existing categories, add new categories and develop SCAVENGER modules for other sorts of data. MAPMAN is used to analyse two sets of 22K Affymetrix arrays that investigate the response of Arabidopsis rosettes to low sugar: one investigates the response to a 6-h extension of the night, and the other compares wild-type Columbia-0 (Col-0) and the starchless pgm mutant (plastid phosphoglucomutase) at the end of the night. There were qualitatively similar responses in both treatments. Many genes involved in photosynthesis, nutrient acquisition, amino acid, nucleotide, lipid and cell wall synthesis, cell wall modification, and RNA and protein synthesis were repressed. Many genes assigned to amino acid, nucleotide, lipid and cell wall breakdown were induced. Changed expression of genes for trehalose metabolism point to a role for trehalose-6-phosphate (Tre6P) as a starvation signal. Widespread changes in the expression of genes encoding receptor kinases, transcription factors, components of signalling pathways, proteins involved in post-translational modification and turnover, and proteins involved in the synthesis and sensing of cytokinins, abscisic acid (ABA) and ethylene revealing large-scale rewiring of the regulatory network is an early response to sugar depletion.
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Motivation: Microsatellites are a widely-used marker system in plant genetics and forensics. The development of reliable microsatellite markers from resequencing data is challenging. Results: We extended MISA, a computational tool assisting the development of microsatellite markers, and reimplemented it as a web-based application. We improved compound microsatellite detection and added the possibility to display and export MISA results in GFF3 format for downstream analysis. Availability and Implementation: MISA-web can be accessed under http://misaweb.ipk-gatersleben.de/. The website provides tutorials, usage note as well as download links to the source code. Contact: scholz@ipk-gatersleben.de.
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Leaf senescence is finely tuned by many regulatory factors such as NAC (NAM/ATAF/CUC) transcription factors (TFs). NACs comprise one of the largest families of TFs in plants, many of which are differentially regulated during leaf senescence and play a major role in leaf senescence. Recent studies advanced our understanding on the structural and functional features of NAC TFs including target binding specificities of the N-terminal DNA binding domain and dynamic interaction of the C-terminal intrinsically disordered domain with other proteins. NAC TFs control other NACs and also interact with NACs or other TFs to fine-tune the expression of target genes. These studies clearly demonstrated the highly complex characteristics of NAC regulatory networks, which are dynamically regulated temporally and spatially and effectively integrate multiple developmental and environmental signals.
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Dendrocalamus sinicus is the world's largest bamboo species with strong woody culms, and known for its fast-growing culms. As an economic bamboo species, it was popularized for multi-functional applications including furniture, construction, and industrial paper pulp. To comprehensively elucidate the molecular processes involved in its culm elongation, Illumina paired-end sequencing was conducted. About 65.08 million high-quality reads were produced, and assembled into 81,744 unigenes with an average length of 723 bp. A total of 64,338 (79%) unigenes were annotated for their functions, of which, 56,587 were annotated in the NCBI non-redundant protein database and 35,262 were annotated in the Swiss-Prot database. Also, 42,508 and 21,009 annotated unigenes were allocated to gene ontology (GO) categories and clusters of orthologous groups (COG), respectively. By searching against the Kyoto Encyclopedia of Genes and Genomes Pathway database (KEGG), 33,920 unigenes were assigned to 128 KEGG pathways. Meanwhile, 8,553 simple sequence repeats (SSRs) and 81,534 single-nucleotide polymorphism (SNPs) were identified, respectively. Additionally, 388 transcripts encoding lignin biosynthesis were detected, among which, 27 transcripts encoding Shikimate O-hydroxycinnamoyltransferase (HCT) specifically expressed in D. sinicus when compared to other bamboo species and rice. The phylogenetic relationship between D. sinicus and other plants was analyzed, suggesting functional diversity of HCT unigenes in D. sinicus. We conjectured that HCT might lead to the high lignin content and giant culm. Given that the leaves are not yet formed and culm is covered with sheaths during culm elongation, the existence of photosynthesis of bamboo culm is usually neglected. Surprisedly, 109 transcripts encoding photosynthesis were identified, including photosystem I and II, cytochrome b6/f complex, photosynthetic electron transport and F-type ATPase, and 24 transcripts were characterized as antenna proteins that regarded as the main tool for capturing light of plants, implying stem photosynthesis plays a key role during culm elongation due to the unavailability of its leaf. By real-time quantitative PCR, the expression level of 6 unigenes was detected. The results showed the expression level of all genes accorded with the transcriptome data, which confirm the reliability of the transcriptome data. As we know, this is the first study underline the D. sinicus transcriptome, which will deepen the understanding of the molecular mechanisms of culm development. The results may help variety improvement and resource utilization of bamboos.
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王身昌, 胡尚连, 曹颖, 等. 梁山慈竹高通量转录组测序及差异表达基因分析[J]. 华北农学报, 2016,31(3):65-71.
分析梁山慈竹及其体细胞突变体的转录组,挖掘功能基因并对其差异表达基因进行筛选和分析,为梁山慈竹遗传改良提供理论依据。利用RNA-Seq技术进行转录组测序,对测序结果进行denovo拼接和功能注释;并对差异表达基因进行筛选及COG、GO、KEGG数据库中进行比对注释,此外,基于Swiss-Prot功能注释结果,分析纤维素和木质素相关功能基因的表达量差异。测序结果表明,共获得86575631条reads,denovo组装得到84741条unigenes,共有49829条被Nr、COG、GO、KEGG、Swiss-Prot注释。从梁山慈竹实生植株(对照)和体细胞突变体No.30这2个测序样本中,筛选出3572条差异表达unigenes,757条差异表达unigenes在COG分类体系中具有详细的蛋白功能释义,2213条差异表达unigenes在GO数据库具有功能定义,385条unigenes被注释到94条KEGGPathways中。纤维素合成相关纤维素合酶、过氧化物酶、泛素连接酶和热休克蛋白在梁山慈竹体细胞突变体No.30中表达量升高,木质素合成相关MYB4、4-香豆酸CoA连接酶、肉桂醇脱氢酶、肉桂酰-CoA还原酶和漆酶在突变体中表达量降低。提供了全面的梁山慈竹转录组信息,获得了一批在梁山慈竹纤维素和木质素生物合成过程中有重要功能的基因序列。
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A software tool was developed for the identification of simple sequence repeats (SSRs) in a barley ( Hordeum vulgare L.) EST (expressed sequence tag) database comprising 24,595 sequences. In total, 1,856 SSR-containing sequences were identified. Trimeric SSR repeat motifs appeared to be the most abundant type. A subset of 311 primer pairs flanking SSR loci have been used for screening polymorphisms among six barley cultivars, being parents of three mapping populations. As a result, 76 EST-derived SSR-markers were integrated into a barley genetic consensus map. A correlation between polymorphism and the number of repeats was observed for SSRs built of dimeric up to tetrameric units. 3'-ESTs yielded a higher portion of polymorphic SSRs (64%) than 5'-ESTs did. The estimated PIC (polymorphic information content) value was 0.45 +/- 0.03. Approximately 80% of the SSR-markers amplified DNA fragments in Hordeum bulbosum, followed by rye, wheat (both about 60%) and rice (40%). A subset of 38 EST-derived SSR-markers comprising 114 alleles were used to investigate genetic diversity among 54 barley cultivars. In accordance with a previous, RFLP-based, study, spring and winter cultivars, as well as two- and six-rowed barleys, formed separate clades upon PCoA analysis. The results show that: (1) with the software tool developed, EST databases can be efficiently exploited for the development of cDNA-SSRs, (2) EST-derived SSRs are significantly less polymorphic than those derived from genomic regions, (3) a considerable portion of the developed SSRs can be transferred to related species, and (4) compared to RFLP-markers, cDNA-SSRs yield similar patterns of genetic diversity.
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Eukaryotic genomes encode thousands of long noncoding RNAs (lncRNAs), which play important roles in essential biological processes. Although lncRNAs function in the nuclear and cytoplasmic compartments, most of them occur in the nucleus, often in association with chromatin. Indeed, many lncRNAs have emerged as key regulators of gene expression and genome stability. Emerging evidence also suggests that lncRNAs may contribute to the organization of nuclear domains. This review briefly summarizes the major types of eukaryotic lncRNAs and provides examples of their mechanisms of action, with focus on plant lncRNAs, mainly in Arabidopsis thaliana, and describes current advances in our understanding of the mechanisms of lncRNA action and the roles of lncRNAs in RNA-dependent DNA methylation and in the regulation of flowering time.
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BACKGROUND: Leaf development is a complex biological process that is accompanied by wide transcriptional changes. Many protein-coding genes have been characterized in plant leaves, but little attention has been given to noncoding RNAs (ncRNAs). Moreover, increasing evidence indicates that an intricate interplay among RNA species, including protein-coding RNAs and ncRNAs, exists in eukaryotic transcriptomes, however, it remains elusive in plant leaves. RESULTS: We detected novel ncRNAs, such as circular RNAs (circRNAs) and long noncoding RNAs (lncRNAs), and further constructed and analyzed their associated competitive endogenous RNA (ceRNA) networks in Arabidopsis leaves. Transcriptome profiling showed extensive changes during leaf development. In addition, comprehensive detection of circRNAs in other plant leaves suggested that circRNAs are widespread in plant leaves. To investigate the complex post-transcriptional interactions in Arabidopsis leaves, we constructed a global circRNA/lncRNA-associated ceRNA network. Functional analysis revealed that ceRNAs were highly correlated with leaf development. These ceRNAs could be divided into six clusters, which were enriched for different functional classes. Stage-specific ceRNA networks were further constructed and comparative analysis revealed different roles of stage common and specific hub ceRNAs. CONCLUSIONS: Our results demonstrate that understanding the ceRNA interactions will lead insights into gene regulations implicated in leaf development.
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郭兆武, 李合松, 王若仲, 等. 高产杂交稻 ‘两优培九’剑叶及其叶鞘的光合作用[J]. 植物生理与分子生物学学报, 2007,33(6):531-537.
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The highly ordered process of senescence forms the final stage of leaf development; a large set of senescence-associated genes (SAGs) execute this orderly dismantling of the photosynthetic apparatus and remobilization of cellular components. A number of transcription factors (TFs) modulate SAG expression to promote or delay senescence. Here we show that NAC016, the previously uncharacterized senescence-associated NAM/ATAF1/2/CUC2 (senNAC) TF in Arabidopsis thaliana, promotes senescence. Leaves of nac016 mutants remained green under senescence-inducing conditions, and leaves of NAC016-overexpressing (NAC016-OX) plants senesced early. Under dark-induced senescence (DIS) conditions, nac016 mutants had low ion leakage, and retained the proper balance of photosystem proteins and normal grana thylakoid shape much longer than wild-type plants, suggesting that nac016 acts as a functional stay-green type senescence mutant. Under DIS conditions, SAGs (NYC1, PPH, SGR1/NYE1 and WRKY22), including senNACs (JUB1, NAP, ORE1, ORS1 and VNI2), were down-regulated in nac016 mutants and up-regulated in NAC016-OX plants. In addition to its role in senescence, NAC016 also affects abiotic stress. Under salt and oxidative stress conditions, NAC016 expression rapidly increased in developing leaves, possibly to promote senescence. Indeed, under the stress conditions, nac016 mutants stayed green and NAC016-OX plants senesced rapidly. To identify direct targets of the NAC016 TF in the regulation of leaf senescence, we conducted yeast one-hybrid assays, which strongly suggested that NAC016 binds to the promoters of NAP and ORS1. Based on these results, we propose that NAC016 regulatory mechanisms promoting leaf senescence exhibit cross-talk with the salt and oxidative stress-responsive signaling pathways.
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| [33] |
NAC with a transmembrane (TM) motif1-like (NTL) transcription factors, containing three regions: the N-terminal NAC domain (ND), the middle regulation region (RR), and the C-terminal TM domain, belong to the tail-anchored proteins. Although these NTLs play numerous essential roles in plants, their subcellular distribution and the mechanism of translocation into the nucleus (NU) remain unclear. In this study, we found that most of the full-length NTLs were localized in the endoplasmic reticulum (ER), with the exception of NTL11 and NTL5, which were restricted to the NU. Furthermore, we found that NTL11 contains a TM domain, whereas NTL5 does not. The ND of all of the NTLs was responsible for nuclear localization in plants. After truncation of the TM domain, NTL8_NR, NTL10_NR and NTL13_NR localized in the cytoplasm (CT) and NU, and other NTL_NRs were only localized in the NU, suggesting that the RR of NTL8, NTL10 and NTL13 contains some inhibitory region to mask the nuclear localization signal sequence in the ND domain and permit their diffusion between CT and NU. Furthermore, the N-terminus of NTL11 was translocated to the NU, but the C-terminus was degraded in Arabidopsis mesophyll protoplasts. The chimeric construct of NTL11_ND with NTL10_RR and TM domain (11ND-10RT) was localized exclusively in the ER, and not in the NU. However, 10ND-11RT was found mainly in the NU. Our results indicated that the TM domain is essential for NTL targeting the ER and the N-terminal fragment, including ND and RR, is translocated into the NU after activation through proteolytic cleavage events upon stimulation by internal and external environmental signals.
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| [34] |
Plants require daily coordinated regulation of energy metabolism for optimal growth and survival and therefore need to integrate cellular responses with both mitochondrial and plastid retrograde signaling. Using a forward genetic screen to characterize regulators of alternative oxidase1a (rao) mutants, we identified RAO2/Arabidopsis NAC domain-containing protein17 (ANAC017) as a direct positive regulator of AOX1a. RAO2/ANAC017 is targeted to connections and junctions in the endoplasmic reticulum (ER) and F-actin via a C-terminal transmembrane (TM) domain. A consensus rhomboid protease cleavage site is present in ANAC017 just prior to the predicted TM domain. Furthermore, addition of the rhomboid protease inhibitor N-p-Tosyl-l-Phe chloromethyl abolishes the induction of AOX1a upon antimycin A treatment. Simultaneous fluorescent tagging of ANAC017 with N-terminal red fluorescent protein (RFP) and C-terminal green fluorescent protein (GFP) revealed that the N-terminal RFP domain migrated into the nucleus, while the C-terminal GFP tag remained in the ER. Genome-wide analysis of the transcriptional network regulated by RAO2/ANAC017 under stress treatment revealed that RAO2/ANAC017 function was necessary for >85% of the changes observed as a primary response to cytosolic hydrogen peroxide (H2O2), but only ~33% of transcriptional changes observed in response to antimycin A treatment. Plants with mutated rao2/anac017 were more stress sensitive, whereas a gain-of-function mutation resulted in plants that had lower cellular levels of H2O2 under untreated conditions.
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| [35] |
Leaf senescence is a unique developmental process that is characterized by massive programmed cell death and nutrient recycling. The underlying molecular regulatory mechanisms are not well understood. Here we report the functional analysis of AtNAP, a gene encoding a NAC family transcription factor. Expression of this gene is closely associated with the senescence process of Arabidopsis rosette leaves. Leaf senescence in two T-DNA insertion lines of this gene is significantly delayed. The T-DNA knockout plants are otherwise normal. The mutant phenotype can be restored to wild-type by the intact AtNAP, as well as by its homologs in rice and kidney bean plants that are also upregulated during leaf senescence. Furthermore, inducible overexpression of AtNAP causes precocious senescence. These data strongly suggest that AtNAP and its homologs play an important role in leaf senescence in Arabidopsis and possibly in other plant species.
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| [36] |
The transition from juvenility through maturation to senescence is a complex process that involves the regulation of longevity. Here, we identify JUNGBRUNNEN1 (JUB1), a hydrogen peroxide (H(2)O(2))-induced NAC transcription factor, as a central longevity regulator in Arabidopsis thaliana. JUB1 overexpression strongly delays senescence, dampens intracellular H(2)O(2) levels, and enhances tolerance to various abiotic stresses, whereas in jub1-1 knockdown plants, precocious senescence and lowered abiotic stress tolerance are observed. A JUB1 binding site containing a RRYGCCGT core sequence is present in the promoter of DREB2A, which plays an important role in abiotic stress responses. JUB1 transactivates DREB2A expression in mesophyll cell protoplasts and transgenic plants and binds directly to the DREB2A promoter. Transcriptome profiling of JUB1 overexpressors revealed elevated expression of several reactive oxygen species-responsive genes, including heat shock protein and glutathione S-transferase genes, whose expression is further induced by H(2)O(2) treatment. Metabolite profiling identified elevated Pro and trehalose levels in JUB1 overexpressors, in accordance with their enhanced abiotic stress tolerance. We suggest that JUB1 constitutes a central regulator of a finely tuned control system that modulates cellular H(2)O(2) level and primes the plants for upcoming stress through a gene regulatory network that involves DREB2A.
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| [37] |
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| [38] |
Leaf aging is a highly regulated developmental process, which is also influenced profoundly by diverse environmental conditions. Accumulating evidence in recent years supports that plant responsiveness to abiotic stress is intimately related with leaf longevity. However, molecular mechanisms underlying the signaling crosstalks and regulatory schemes are yet unknown. In this work, we demonstrate that an abscisic acid (ABA)-responsive NAC transcription factor VND-INTERACTING2 (VNI2) integrates ABA-mediated abiotic stress signals into leaf aging by regulating a subset of COLD-REGULATED (COR) and RESPONSIVE TO DEHYDRATION (RD) genes. The VNI2 gene was induced by high salinity in an ABA-dependent manner. In addition, spatial and temporal expression patterns of the VNI2 gene are correlated with leaf aging and senescence. Accordingly, leaf aging was delayed in transgenic plants overexpressing the VNI2 gene but significantly accelerated in a VNI2-deficient mutant. The VNI2 transcription factor regulates the COR and RD genes by binding directly to their promoters. Notably, transgenic plants overexpressing the COR or RD genes exhibited prolonged leaf longevity. These observations indicate that the VNI2 transcription factor serves as a molecular link that integrates plant responses to environmental stresses into modulation of leaf longevity.
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