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Systemic acquired resistance (SAR), an inducible plant-defense response to local infection, requires the signaling molecule salicylic acid (SA) and the transcriptional coactivator NPR1, with concerted activation of pathogenesis-related (PR) genes. Arabidopsis sni1 is an npr1 suppressor and derepression of defense genes in sni1 causes reduced growth...
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... suppressor screen was designed to search for mutants that resembled wild-type in morphology and had abolished the background expression of PR genes in sni1. As shown in Figure 1A, ssn2 restored wild-type morphology to both sni1 and sni1npr1. The elevated background expression of the SA-responsive BGL2:GUS reporter in sni1 and sni1npr1 was also suppressed in sni1ssn2 and sni1npr1ssn2. ...
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... elevated background expression of the SA-responsive BGL2:GUS reporter in sni1 and sni1npr1 was also suppressed in sni1ssn2 and sni1npr1ssn2. Moreover, in sni1npr1ssn2, the reporter gene lost its responsiveness to exogenous application of a SA functional analog INA (2,6-di- chloroisonicotinic acid) ( Figure 1A). A time course expression analysis performed on the PR1 gene also showed a significant delay in gene induction in the ssn2 single mutant ( Figure 1B). ...
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... in sni1npr1ssn2, the reporter gene lost its responsiveness to exogenous application of a SA functional analog INA (2,6-di- chloroisonicotinic acid) ( Figure 1A). A time course expression analysis performed on the PR1 gene also showed a significant delay in gene induction in the ssn2 single mutant ( Figure 1B). ...
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... determine whether the effect of ssn2 is restricted to BGL2:GUS and PR1 or general to the transcription reprogram- ming during plant defense, we performed microarrays on sni1npr1 and sni1npr1ssn2 with and without SA treatment. As shown in Figure 1C, among the 270 genes significantly induced in sni1npr1 (p value < 0.05), 147 (54.4%) were dependent on SSN2 (Document S2, available online). Gene ontology analysis found 31 defense-related genes in the SSN2-dependent group (21.1%) and 14 in the SSN2-independent group (11.4%). ...
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... ontology analysis found 31 defense-related genes in the SSN2-dependent group (21.1%) and 14 in the SSN2-independent group (11.4%). We also performed qPCR on nine well-known defense genes de- tected in the microarray and found that SA induction of genes such as PR1, PR2, PR5, EDS1, and PAD4 was diminished by the ssn2 mutation ( Figure S1A). ...
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... ssn2 mutation was mapped to the At4g33925 locus (Fig- ure S1B). Through sequencing analysis, a 3.4 kb gypsy-like ret- rotransposon insertion was identified in the first exon of At4g33925 in ssn2-1 ( Figures S1C and S1D). ...
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... ssn2 mutation was mapped to the At4g33925 locus (Fig- ure S1B). Through sequencing analysis, a 3.4 kb gypsy-like ret- rotransposon insertion was identified in the first exon of At4g33925 in ssn2-1 ( Figures S1C and S1D). A $40 kb deletion and a large DNA rearrangement were found in the chromosomal region of At4g33925 for ssn2-2 and ssn2-3, respectively. ...
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... ssn2-1 allele was selected for further experiments and is here- after referred to as ssn2. To confirm that At4g33925 is SSN2, we transformed the genomic DNA containing the entire At4g33925 gene into sni1ssn2, and the resulting homozygous transgenic lines restored the sni1 morphology and the back- ground BGL2:GUS expression ( Figure 1A). ...
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... of SSN2 have been found in all eukaryotes (Martín et al., 2006). Confocal fluorescence microscopic examination of transgenic plants expressing a functional 35S:SSN2-GFP transgene showed that SSN2 was predominantly localized in the nucleus (Figure S1E), similar to SNI1 (Mosher et al., 2006). By using a fusion of the SSN2 promoter to the GUS reporter, SSN2 gene expression was detected in leaves, predominantly in shoot apexes. ...
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... using a fusion of the SSN2 promoter to the GUS reporter, SSN2 gene expression was detected in leaves, predominantly in shoot apexes. Moderate expression of SSN2 was also observed in roots ( Figure S1F). ...
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... ES4326 (Psm ES4326). As shown in Figure 1D, there was an increase in growth of Psm ES4326 in the ssn2 single mutant. This defect in resistance was more pronounced in the npr1ssn2 double ( Figure S1G) and sni1npr1ssn2 triple ( Figure 1D) mutants. ...
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... shown in Figure 1D, there was an increase in growth of Psm ES4326 in the ssn2 single mutant. This defect in resistance was more pronounced in the npr1ssn2 double ( Figure S1G) and sni1npr1ssn2 triple ( Figure 1D) mutants. To monitor the dynamic change of SSN2 protein levels in response to SA, we generated stable transgenic lines containing the SSN2-TAP (tandem affinity purification) fusion construct driven by the native SSN2 promoter. ...
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... shown in Figure 1D, there was an increase in growth of Psm ES4326 in the ssn2 single mutant. This defect in resistance was more pronounced in the npr1ssn2 double ( Figure S1G) and sni1npr1ssn2 triple ( Figure 1D) mutants. To monitor the dynamic change of SSN2 protein levels in response to SA, we generated stable transgenic lines containing the SSN2-TAP (tandem affinity purification) fusion construct driven by the native SSN2 promoter. ...
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... monitor the dynamic change of SSN2 protein levels in response to SA, we generated stable transgenic lines containing the SSN2-TAP (tandem affinity purification) fusion construct driven by the native SSN2 promoter. To confirm the functionality of SSN2:SSN2-TAP, we crossed a transgenic line with sni1ssn2 and the homozygous sni1ssn2 progeny containing SSN2:SSN2-TAP regained the sni1 pheno- type, indicating that the SSN2-TAP fusion protein is biologically active ( Figure S1H). The SSN2:SSN2-TAP lines were treated with 0.5 mM SA and the SSN2-TAP fusion protein was analyzed at different time points. ...
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... SSN2:SSN2-TAP lines were treated with 0.5 mM SA and the SSN2-TAP fusion protein was analyzed at different time points. As shown in Figure 1E, levels of SSN2- TAP protein were upregulated by SA with the highest expression at 8 hr after treatment. This SA-inducible nature of the SSN2 protein, together with the disease phenotype of the ssn2 mutant, suggests that SSN2 plays a positive role in defense responses. ...
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... DNA damage repair and defense phenotypes detected in ssn2 and rad51d (Durrant et al., 2007) lead us to ask how the SSN2-RAD51D repair complex affects plant immunity. The compromised basal expression of the BGL2:GUS reporter in sni1ssn2 ( Figure 1A) and sni1rad51d ( Durrant et al., 2007), the delayed expression of the PR1 gene ( Figure 1B) in the ssn2 single mutant, and the significant blockage in SA induction of defense genes observed in sni1npr1ssn2 by microarray ( Figure 1C) suggest that the SSN2-RAD51D complex may affect defense at the transcriptional level. To determine whether SNI1 and SSN2-RAD51D are directly involved in repressing and acti- vating PR gene expression, respectively, we performed a series of chromatin immunoprecipitation (ChIP) experiments by using a set of probes covering both the promoter and the coding regions of PR1 ( Figure 4A). ...
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... DNA damage repair and defense phenotypes detected in ssn2 and rad51d (Durrant et al., 2007) lead us to ask how the SSN2-RAD51D repair complex affects plant immunity. The compromised basal expression of the BGL2:GUS reporter in sni1ssn2 ( Figure 1A) and sni1rad51d ( Durrant et al., 2007), the delayed expression of the PR1 gene ( Figure 1B) in the ssn2 single mutant, and the significant blockage in SA induction of defense genes observed in sni1npr1ssn2 by microarray ( Figure 1C) suggest that the SSN2-RAD51D complex may affect defense at the transcriptional level. To determine whether SNI1 and SSN2-RAD51D are directly involved in repressing and acti- vating PR gene expression, respectively, we performed a series of chromatin immunoprecipitation (ChIP) experiments by using a set of probes covering both the promoter and the coding regions of PR1 ( Figure 4A). ...
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... DNA damage repair and defense phenotypes detected in ssn2 and rad51d (Durrant et al., 2007) lead us to ask how the SSN2-RAD51D repair complex affects plant immunity. The compromised basal expression of the BGL2:GUS reporter in sni1ssn2 ( Figure 1A) and sni1rad51d ( Durrant et al., 2007), the delayed expression of the PR1 gene ( Figure 1B) in the ssn2 single mutant, and the significant blockage in SA induction of defense genes observed in sni1npr1ssn2 by microarray ( Figure 1C) suggest that the SSN2-RAD51D complex may affect defense at the transcriptional level. To determine whether SNI1 and SSN2-RAD51D are directly involved in repressing and acti- vating PR gene expression, respectively, we performed a series of chromatin immunoprecipitation (ChIP) experiments by using a set of probes covering both the promoter and the coding regions of PR1 ( Figure 4A). ...
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Citations
... encoded DNA polymerase III, mainly known for DNA replications and repairing DNA damaged by hydrogen peroxide [56]. The DNA repair process was a part of the plant immune response [57], especially in the infection of B. oryzae that hydrogen peroxide was shown to accumulate in a leaf [23]. Pavir.3KG358400 ...
Switchgrass (Panicum virgatum L.), a northern native perennial grass, suffers from yield reduction from Bipolaris leaf spot caused by Bipolaris oryzae (Breda de Haan) Shoemaker. This study aimed to determine the resistant populations via multiple phenotyping approaches and identify potential resistance genes from genome-wide association studies (GWAS) in the switchgrass northern association panel. The disease resistance was evaluated from both natural (field evaluations in Ithaca, New York and Phillipsburg, Philadelphia) and artificial inoculations (detached leaf and leaf disk assays). The most resistant populations based on a combination of three phenotyping approaches—detached leaf, leaf disk, and mean from two locations—were ‘SW788’, ‘SW806’, ‘SW802’, ‘SW793’, ‘SW781’, ‘SW797’, ‘SW798’, ‘SW803’, ‘SW795’, ‘SW805’. The GWAS from the association panel showed 27 significant SNPs on 12 chromosomes: 1K, 2K, 2N, 3K, 3N, 4N, 5K, 5N, 6N, 7K, 7N, and 9N. These markers accumulatively explained the phenotypic variance of the resistance ranging from 3.28 to26.52%. Within linkage disequilibrium of 20 kb, these SNP markers linked with the potential resistance genes included the genes encoding for NBS-LRR, PPR, cell-wall related proteins, homeostatic proteins, anti-apoptotic proteins, and ABC transporter.
... In Arabidopsis, RAD51 and RAD51D appear to play a direct role in inducing defense gene transcription and interact physically with transcription start sites. Additionally, RAD51D interacts physically with the defense gene suppressor SNI1 [20,[24][25][26]. SNI1 itself, although first discovered as a negative regulator of defense, is also involved in meiotic recombination; sni1 mutant Arabidopsis displays increased rates of crossover formation [27]. ...
... These transcription factors (aligning with peptides 1 and 2), which contain a conserved amino acid motif beginning with WRKY, can be involved in regulating response to a range of biotic and abiotic stresses in plants, including pathogens [36]. The negative recombination regulator SNI1, which also serves as a defense gene regulator, appears to interact physically with several WRKY transcription factors in Arabidopsis [25,27,36,37]. Synthesized peptide #30, which was developed from the transcription factor MYC2, also binds RAD51A1 in vitro. ...
... Some peptides were blotted twice. Peptides 1,2,3,7,8,11,12,15,18,19,20,25,30, and 31 bound to RAD51A1. These 14 peptides are listed in Table 4. Note: Two dot blotting experiments were conducted due to the availability of synthesized peptides, GenScript provided two batches of peptide products Authors' contributions CC, BD designed this study. ...
Background
RAD51 proteins, which are conserved in all eukaryotes, repair DNA double-strand breaks. This is critical to homologous chromosome pairing and recombination enabling successful reproduction. Work in Arabidopsis suggests that RAD51 also plays a role in plant defense; the Arabidopsis rad51 mutant is more susceptible to Pseudomonas syringae . However, the defense functions of RAD51 and the proteins interacting with RAD51 have not been thoroughly investigated in maize. Uncovering ligands of RAD51 would help to understand meiotic recombination and possibly the role of RAD51 in defense. This study used phage display, a tool for discovery of protein-protein interactions, to search for proteins interacting with maize RAD51A1.
Results
Maize RAD51A1 was screened against a random phage library. Eleven short peptide sequences were recovered from 15 phages which bound ZmRAD51A1 in vitro ; three sequences were found in multiple successfully binding phages. Nine of these phage interactions were verified in vitro through ELISA and/or dot blotting.
BLAST searches did not reveal any maize proteins which contained the exact sequence of any of the selected phage peptides, although one of the selected phages had a strong alignment (E-value = 0.079) to a binding domain of maize BRCA2. Therefore, we designed 32 additional short peptides using amino acid sequences found in the predicted maize proteome. These peptides were not contained within phages. Of these synthesized peptides, 14 bound to ZmRAD51A1 in a dot blot experiment. These 14 sequences are found in known maize proteins including transcription factors putatively involved in defense.
Conclusions
These results reveal several peptides which bind ZmRAD51A1 and support a potential role for ZmRAD51A1 in transcriptional regulation and plant defense. This study also demonstrates the applicability of phage display to basic science questions, such as the search for binding partners of a known protein, and raises the possibility of an iterated approach to test peptide sequences that closely but imperfectly align with the selected phages.
... For example, while the expression of RAD23C was reduced by all the above five pathogens as well as all the Agrobacterium strains, the expression of RAD23B was reduced by all Agrobacterium strains and Botrytis cinerea, but not others. There are previous reports of DNA repair genes of HR pathway [BRCA2 and RAD51 (Wang et al. 2010), SSN2 and RAD51D (Song et al. 2011;Durrant et al. 2007), RAD17 and ATR (Yan et al. 2013)] regulating defence genes involved in systemic acquired resistance. The absence of the same genes [BRCA2, RAD51 (Wang et al. 2010), SSN2 (Song et al. 2011), RAD51D (Durrant et al. 2007), RAD17 and ATR (Yan et al. 2013)] in Arabidopsis mutants deficient of the respective genes rendered the plants susceptible to bacterial pathogen Pseudomonas syringae pv. ...
... There are previous reports of DNA repair genes of HR pathway [BRCA2 and RAD51 (Wang et al. 2010), SSN2 and RAD51D (Song et al. 2011;Durrant et al. 2007), RAD17 and ATR (Yan et al. 2013)] regulating defence genes involved in systemic acquired resistance. The absence of the same genes [BRCA2, RAD51 (Wang et al. 2010), SSN2 (Song et al. 2011), RAD51D (Durrant et al. 2007), RAD17 and ATR (Yan et al. 2013)] in Arabidopsis mutants deficient of the respective genes rendered the plants susceptible to bacterial pathogen Pseudomonas syringae pv. maculicola. ...
Agrobacterium tumefaciens is a unique pathogen with the ability to transfer a portion of its DNA, the T-DNA, to other organisms. The role of DNA repair genes in Agrobacterium transformation remains controversial. In order to understand if the host DNA repair response and dynamics was specific to bacterial factors such as Vir proteins, T-DNA, and oncogenes, we profiled the expression and promoter methylation of various DNA repair genes. These genes belonged to nucleotide excision repair (NER), base excision repair (BER), mismatch repair (MMR), homologous recombination (HR), and non-homologous end joining (NHEJ) pathways. We infected Arabidopsis plants with different Agrobacterium strains that lacked one or more of the above components so that the influence of the respective factors could be analysed. Our results revealed that the expression and promoter methylation of most DNA repair genes was affected by Agrobacterium, and it was specific to Vir proteins, T-DNA, oncogenes, or the mere presence of bacteria. In order to determine if Agrobacterium induced any transgenerational epigenetic effect on the DNA repair gene promoters, we studied the promoter methylation in two subsequent generations of the infected plants. Promoters of at least three genes, CEN2, RAD51, and LIG4 exhibited transgenerational memory in response to different bacterial factors. We believe that this is the first report of Agrobacterium-induced transgenerational epigenetic memory of DNA repair genes in plants. In addition, we show that Agrobacterium induces short-lived DNA strand breaks in Arabidopsis cells, irrespective of the presence or absence of virulence genes and T-DNA.
... Plants treated with SA display DNA damage accumulation (Yan et al., 2013) and increased HR rates (Kovalchuk et al., 2003). Consistently, mutants affected in DSB repair by HR, such as rad51 or brca2, show increased susceptibility to P. syringae (Durrant et al., 2007;Song et al., 2011). ...
... A subunit of the STRUCTURAL MAINTENANCE OF CHROMOSOME (SMC) complex, which is involved in the DDR facilitating DSB repair, collapsed replication fork restart, and telomere elongation by HR (Potts, 2009;Yan et al., 2013), was initially identified as a master regulator of the SA-mediated defense response and named SUPPRES-SOR OF NPR1-1, INDUCIBLE 1 (SNI1) (Cao et al., 1997;Li et al., 1999). The sni1 mutation leads to endogenous DNA damage and pathogen resistance, which could be suppressed by the mutation of DDR genes (such as RAD51D, BRCA2A, and RAD51) and DNA damage sensor genes (RAD17 and ATR) (Durrant et al., 2007;Song et al., 2011;Wang et al., 2010), demonstrating that the DDR positively regulates plant immunity responses. ...
Being sessile organisms, plants are ubiquitously exposed to stresses that can affect the DNA replication process or cause DNA damage. To cope with these problems, plants utilize DNA damage response (DDR) pathways, consisting of both highly conserved and plant-specific elements. As a part of this DDR, cell cycle checkpoint control mechanisms either pause the cell cycle, to allow DNA repair, or lead cells into differentiation or programmed cell death, to prevent the transmission of DNA errors in the organism through mitosis or its offspring via meiosis. The two major cell cycle checkpoints control either the replication process or the G2/M transition. The latter is largely overseen by the plant-specific SOG1 transcription factor that drives the activity of cyclin-dependent kinase inhibitors and MYB3R proteins that are rate-limiting for the G2/M transition. By contrast, the replication checkpoint is controlled by different players, including the conserved kinase WEE1, and likely the transcriptional repressor RBR1. These checkpoint mechanisms are called upon during developmental processes, in retrograde signaling pathways, as well as in response to biotic and abiotic stresses, including metal toxicity, cold, salinity and phosphate deficiency. Additionally, the recent expansion of research from Arabidopsis to other model plants has revealed species-specific aspects of the DDR. Overall, it is becoming evidently clear that the DNA damage checkpoint mechanisms represent an important aspect of the adaptation of plants to a changing environment, hence gaining more knowledge about this topic might be helpful to increase the resilience of plants to climate change.
... The precise nature of the relationship between DNA damage response pathways and plant immunity is currently unclear (Yan et al., 2013;Song and Bent, 2014;Rodriguez et al., 2018). Some have reported that DNA damage promotes plant immunity by activating pathways that function in parallel to the ETI pathway described above via SA-independent mechanisms (Li et al., 1999;Durrant et al., 2007;Wang et al., 2010;Song et al., 2011;Yan et al., 2013;Ogita et al., 2018). Consistent with this view, the SOG1 transcription factor directly controls expression of genes involved in plant defense signaling in addition to promoting expression of genes involved in the DNA damage response (Yoshiyama et al., 2013;Ogita et al., 2018). ...
... We found a highly statistically significant overlap between these two gene sets as well ( Figure 5F). Together, these transcriptomic analyses suggest that XCT deficiency in plants or xap5 deficiency in fission yeast might cause alterations in cellular responses to DNA damaging agents, an intriguing possibility given previous reports of the involvement of DNA damage response signaling factors in plant defense responses (Durrant et al., 2007;Wang et al., 2010;Song et al., 2011;Yan et al., 2013;Bourbousse et al., 2018;Ogita et al., 2018). ...
Numerous links have been reported between immune response and DNA damage repair pathways in both plants and animals but the precise nature of the relationship between these fundamental processes is not entirely clear. Here, we report that XAP5 CIRCADIAN TIMEKEEPER (XCT), a protein highly conserved across eukaryotes, acts as a negative regulator of immunity in Arabidopsis thaliana and plays a positive role in responses to DNA damaging radiation. We find xct mutants have enhanced resistance to infection by a virulent bacterial pathogen, Pseudomonas syringae pv. tomato DC3000, and are hyper-responsive to the defense-activating hormone salicylic acid (SA) when compared to wild-type. Unlike most mutants with constitutive effector-triggered immunity (ETI), xct plants do not have increased levels of SA and retain enhanced immunity at elevated temperatures. Genetic analysis indicates XCT acts independently of NONEXPRESSOR OF PATHOGENESIS RELATED GENES1 (NPR1), which encodes a known SA receptor. Since DNA damage has been reported to potentiate immune responses, we next investigated the DNA damage response in our mutants. We found xct seedlings to be hypersensitive to UV-C and γ radiation and deficient in phosphorylation of the histone variant H2A.X, one of the earliest known responses to DNA damage. These data demonstrate that loss of XCT causes a defect in an early step of the DNA damage response pathway. Together, our data suggest that alterations in DNA damage response pathways may underlie the enhanced immunity seen in xct mutants.
... PKR2 regulates multiple processes including cold and salt stress tolerance, flowering and hormonal signaling [49,50]. RAD54 is involved in DNA repair [51], and its enhanced susceptibility phenotype is reminiscent of those of other DNA repair machinery mutants [52]. CHR17, together with the closely related gene CHR11, are involved in controlling plant development [37, [53][54][55]. ...
Perception of microbes by plants leads to dynamic reprogramming of the transcriptome, which is essential for plant health. The appropriate amplitude of this transcriptional response can be regulated at multiple levels, including chromatin. However, the mechanisms underlying the interplay between chromatin remodeling and transcription dynamics upon activation of plant immunity remain poorly understood. Here, we present evidence that activation of plant immunity by bacteria leads to nucleosome repositioning, which correlates with altered transcription. Nucleosome remodeling follows distinct patterns of nucleosome repositioning at different loci. Using a reverse genetic screen, we identify multiple chromatin remodeling ATPases with previously undescribed roles in immunity, including EMBRYO SAC DEVELOPMENT ARREST 16, EDA16. Functional characterization of the immune-inducible chromatin remodeling ATPase EDA16 revealed a mechanism to negatively regulate immunity activation and limit changes in redox homeostasis. Our transcriptomic data combined with MNase-seq data for EDA16 functional knock-out and over-expressor mutants show that EDA16 selectively regulates a defined subset of genes involved in redox signaling through nucleosome repositioning. Thus, collectively, chromatin remodeling ATPases fine-tune immune responses and provide a previously uncharacterized mechanism of immune regulation.
... The SNP locus S02_65282291 is within a single strand DNA repair-like protein. The DNA repair proteins are known to be directly involved in regulation of gene expression during plant immune response (Song et al., 2011). ...
Anthracnose disease of sorghum is caused by Colletotrichum sublineola, a filamentous fungus. The genetic basis of resistance to anthracnose in sorghum is largely unclear, especially in Senegalese sorghum germplasm. In this study, 163 Senegalese sorghum accessions were evaluated for response to C. sublineola, and a genome‐wide association study (GWAS) was performed to identify genetic variation associated with response to C. sublineola using 193,727 single nucleotide polymorphisms (SNPs) throughout the genome. Germplasm diversity analysis showed low genetic diversity and slow linkage disequilibrium (LD) decay among the Senegalese accessions. Phenotypic analysis resulted in relatively low differences to C. sublineola among the tested population. Genome‐wide association study did not identify any significant association based on a strict threshold for the number of SNPs available. However, individual analysis of the top eight SNPs associated with relative susceptibility and resistance identified candidate genes that have been shown to play important roles in plant stress tolerance in previous studies. This study identifies sorghum genes whose annotated properties have known roles in host defense and thus identify them as candidates for use in breeding for resistance to anthracnose.
... Links between the DNA damage response (DDR), cell cycle, programed cell death, and immunity have emerged in recent years (Song et al., 2011;Yan et al., 2013;Johnson et al., 2018). Depending on the cell type and the severity of the DNA damage, different cellular responses are triggered. ...
Recognition and repair of damaged tissue are an integral part of life. The failure of cells and tissues to appropriately respond to damage can lead to severe dysfunction and disease. Therefore, it is essential that we understand the molecular pathways of wound recognition and response. In this review, we aim to provide a broad overview of the molecular mechanisms underlying the fate of damaged cells and damage recognition in plants. Damaged cells release the so-called damage associated molecular patterns to warn the surrounding tissue. Local signaling through calcium (Ca²⁺), reactive oxygen species (ROS), and hormones, such as jasmonic acid, activates defense gene expression and local reinforcement of cell walls to seal off the wound and prevent evaporation and pathogen colonization. Depending on the severity of damage, Ca²⁺, ROS, and electrical signals can also spread throughout the plant to elicit a systemic defense response. Special emphasis is placed on the spatiotemporal dimension in order to obtain a mechanistic understanding of wound signaling in plants.
... In this network, two newly identified DNA damage proteins, SSN2 and RAD51D, interacts with SNI1, a negative regulator of NPR1 (a key regulator of the salicylic acidmediated SAR), to regulate pathogen-related gene expression. These pieces of evidence show that FRO8 may be downstream genes of SA-mediated SAR (Song et al., 2011). ...
Subcellular iron homeostasis genes (SIHGs) (Vacuolar iron transporter 1 (VIT1),
natural resistance-associated macrophage protein 3 and 4 (NRAMP3 and NRAMP4),
ferric chelate reductase 7 and 8 (FRO7 and FRO8), and Permease in chloroplasts
(PIC1) take part in sequestration, translocation and remobilization of iron between
compartmentalized organs and cytoplasm. Therefore, to shed light on these genes’
functions in different biological processes, in silico analyses of these proteins were
conducted. Posttranslational modification (PTMs) analysis showed that all SIHGs
can be dynamically regulated due to variations in their phosphorylation sites. The
evolutionary tree of SIHGs revealed that VIT1, NRAMP3, and NRAMP4 may be
derived from a common ancestral protein. In Protein-Protein Interaction (PPI)
network analysis, the VIT1 gene was identified as an essential gene in subcellular
iron homeostasis in Arabidopsis. Expression and co-expression analyses showed that
these proteins may be components of various metabolic pathways, in a way
explained as follows: NRAMP3 may be involved in starch metabolism, pathogen
defense mechanism, and nutrient mobilization in senescence, and interact with
aldehyde dehydrogenases (ADH), a protein superfamily regulating plant growth
stages and regulated by abiotic stress mechanism. NRAMP4 is involved in iron
uptake mechanism, acclimation, and stratification processes in dormant seeds with
the stimulation of ethylene and CBFs. The VIT1 expression may be regulated by
nicotianamide (NA). Salicylic acid (SA), as a plant hormone, may be the key
activator of PIC1 expression. PIC1 appears to have taken part in DNA repair,
pathogen response mechanisms, and sugar metabolism. Additionally, PIC1 may have
vital roles in the cellular redox environment, in particular, chloroplast development.
FRO8 may take part in SA-mediated systemic acquired resistance (SAR) network
and DNA double-strand break repair mechanism. Lastly, similar to PIC1, FRO7 may
be a component in DNA repair, SA, and pathogen defense mechanisms as well.
... It is possible that the cell death in flag leaf tips of Frontana and Fielder is regulated by DNA repairing capacity. DNA repairing genes including RAD50 and RAD51 have been identified in yeast, animals and plants and they are involved in various processes such as DNA damage repairing, DNA replication, meiosis, and telomere maintenance (BLEUYARD & al. 2005;LLOYD & al. 2007;SONG & al. 2011]. To examine whether RAD50 and RAD51 contribute to the difference of the leaf tip cell death between Fielder and Frontana, their expression levels was examined by RT-PCR (Figure 3). ...
Wheat stripe rust pandemics have been recorded across all cereal growing regions. Lr34 provides an adult plant resistance and flag leaves of many wheat cultivars containing Lr34 develop a necrotic flag leaf tip. We studied cell death process in progressive necrotic and non-necrotic tissues of flag leaves in wheat cultivars Frontana (resistant to stripe rust) and Fielder (highly susceptible to stripe rust). Cleavage of the poly(ADP-ribose) polymerase (PARP) was detected in necrotic tissues of Frontana flag leaves but not in the non-necrotic tissues or in the corresponding leaf sections in Fielder flag leaves. DNA repairing genes were also studied but their expression was similar in the two different leaf sections for both cultivars. Our work may indicate that protein cleavage is involved in the cell death of flag leaf tips in Frontana.
