Function In Disease Resistance Research Articles

QTL Mapping-Based Identification of Visceral White-Nodules Disease Resistance Genes in Larimichthys polyactis.

Disease outbreaks in aquaculture have recently intensified. In particular, visceral white-nodules disease, caused by Pseudomonas plecoglossicida, has severely hindered the small yellow croaker (Larimichthys polyactis) aquaculture industry. However, research on this disease is limited. To address this gap, the present study employed a 100K SNP chip to genotype individuals from an F1 full-sib family, identify single nucleotide polymorphisms (SNPs), and construct a genetic linkage map for this species. A high-density genetic linkage map spanning a total length of 1395.72 cM with an average interval of 0.08 cM distributed across 24 linkage groups was obtained. Employing post-infection survival time as an indicator of disease resistance, 13 disease resistance-related quantitative trait loci (QTLs) were detected, and these regions included 169 genes. Functional enrichment analyses pinpointed 11 candidate disease resistance-related genes. RT-qPCR analysis revealed that the genes of chmp1a and arg1 are significantly differentially expressed in response to P. plecoglossicida infection in spleen and liver tissues, indicating their pivotal functions in disease resistance. In summary, in addition to successfully constructing a high-density genetic linkage map, this study reports the first QTL mapping for visceral white-nodules disease resistance. These results provide insight into the intricate molecular mechanisms underlying disease resistance in the small yellow croaker.

Genome-wide identification of Saccharum Sec14-like PITP gene family reveals that ScSEC14-1 is positively involved in disease resistance

Phosphatidylinositol transfer protein (PITP) plays an important role in lipid metabolism and plant immune response, however its function is less well-known in sugarcane (Saccharum spp.). In this study, 51 SsPITP genes clustered into four groups (I, III, IV, and V), were identified in S. spontaneum. Results showed that expansion of the SsPITP gene family was mainly through whole genome/segmental replication and dispersed replication events, while purification selection was the main driving force for its evolution. Besides, the SsPITP gene family contained cis-regulatory elements related to light, hormone, and stress response in promoter regions. Interestingly, SsPITPs were differentially expressed under Sporisorium scitamineum stress. Furthermore, due to the continuous high expression of SsPITP29 in the sugarcane resistant variety after being infected with S. scitamineum, its homologous gene ScSEC14–1 with 99.69 % amino acid identity was cloned from the sugarcane hybrid cultivar. The results of transient expression in tobacco epidermal cells showed that the ScSEC14–1 protein was localized on the cell membrane and nucleus. Notably, overexpression of ScSEC14–1 increased the expression of phospholipase C genes in transgenic plants by activating the phosphatidylinositol/calcium/MAPK signaling pathways and plant hormone signal transduction, increasing chlorophyll content and catalase activity, reducing malondialdehyde content, thus enhancing disease resistance. This work will help to systematically understand the characteristics of sugarcane Sec14-like PITP gene family and the disease resistance function of the ScSEC14–1.

Functional Analysis of RMA3 in Response to Xanthomonas citri subsp. citri Infection in Citron C-05 (Citrus medica)

Citrus bacterial canker disease, caused by Xanthomonas citri subsp. citri (Xcc), poses a significant global threat to the citrus industry. Lateral organ boundaries 1 (Lob1) is confirmed as a citrus susceptibility gene that induces pathogenesis by interaction with the PthA4 effector of Xcc. Citron C-05 (Citrus medica) is a Citrus genotype resistant to Xcc. However, there is little information available on the regulation of Lob1 in resistant genotypes, which is important for the breeding of citrus cultivars resistant to canker disease. This study aimed to identify upstream regulatory factors of Lob1 in Citron C-05 and to investigate its function in disease resistance. ‘Bingtang’ sweet orange (C. sinensis), a susceptible genotype, was utilized as the control. cDNA yeast libraries of Xcc-induced Citron C-05 and ‘Bingtang’ sweet orange were constructed. The capacities of ‘Bingtang’ and Citron C-05 were 1.896 × 107 and 2.154 × 107 CFU, respectively. The inserted fragments ranged from 500 to 2000 bp with a 100% recombination rate. The promoter of Lob1 was segmented into two pieces and the P1 fragment from both genotypes was used to construct a bait yeast (PAbAi-CsLob1-P1; PAbAi-CmLob1-P1). Through library screening with the bait yeast, upstream regulators interacting with the Lob1-P1 promoter were identified and then validated using Y1H and dual-luciferase tests. The expression analysis of the three transcript factors indicated that RMA3 was upregulated by inoculation with Xcc in the resistant Citron C-05, but not in the susceptible sweet orange. The overexpression of CsRMA3 in ‘Bingtang’ sweet orange led to reduced canker symptoms, with a significantly lower pathogen density in the leaves following Xcc inoculation. When CmRMA3 was silenced by virus-induced gene silencing (VIGS) in Citron C-05, typical canker symptoms appeared on the CmRMA3-silenced leaves at 15 days post-inoculation with Xcc. Further expression analyses revealed that the CmRMA3 transcription factor suppressed the expression of Lob1. These results suggest that RMA3 participates in the resistant reaction of Citron C-05 to Xcc infection, and such a response might be in relation to its suppression of the expression of the pathogenic gene Lob1.

Sugarcane ScCAX4 is a Negative Regulator of Resistance to Pathogen Infection.

Calcium (Ca2+) is a second messenger in various physiological processes within plants. The significance of the Ca2+/H+ exchanger (CAX) has been established in facilitating Ca2+ transport in plants; however, disease resistance functions of the CAX gene remain elusive. In this study, we conducted sequence characterization and expression analysis for a sugarcane CAX gene, ScCAX4 (GenBank Accession Number: MW206380). In order to further investigate the disease resistance functions, this gene was then transiently overexpressed in Nicotiana benthamiana leaves, which were subsequently inoculated with Fusarium solani var. coeruleum. Results showed that ScCAX4 overexpression increased the susceptibility of N. benthamiana to pathogen infection by regulating the expression of genes related to salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) pathways, suggesting its negative role in disease resistance. Furthermore, we genetically transformed the ScCAX4 gene into N. benthamiana and obtained three positive T2 generation lines. Interestingly, the symptomatology of transgenic plants was consistent with that of transient overexpression after pathogen inoculation. Notably, the JA content in transgenic overexpression lines was significantly higher than that in the wild-type. RNA-seq revealed that ScCAX4 could mediate multiple signaling pathways, and the JA signaling pathway played a key role in modulating disease resistance. Finally, a regulatory model was depicted for the increased susceptibility to pathogen infection conferred by the ScCAX4 gene. This study provides genetic resources for sugarcane molecular breeding and the research direction for plant CAX genes.

Glutamate Receptor-like (GLR) Family in Brassica napus: Genome-Wide Identification and Functional Analysis in Resistance to Sclerotinia sclerotiorum.

Plant glutamate receptor-like channels (GLRs) are homologs of animal ionotropic glutamate receptors. GLRs are critical in various plant biological functions, yet their genomic features and functions in disease resistance remain largely unknown in many crop species. Here, we report the results on a thorough genome-wide study of the GLR family in oilseed rape (Brassica napus) and their role in resistance to the fungal pathogen Sclerotinia sclerotiorum. A total of 61 GLRs were identified in oilseed rape. They comprised three groups, as in Arabidopsis thaliana. Detailed computational analyses, including prediction of domain and motifs, cellular localization, cis-acting elements, PTM sites, and amino acid ligands and their binding pockets in BnGLR proteins, unveiled a set of group-specific characteristics of the BnGLR family, which included chromosomal distribution, motif composition, intron number and size, and methylation sites. Functional dissection employing virus-induced gene silencing of BnGLRs in oilseed rape and Arabidopsis mutants of BnGLR homologs demonstrated that BnGLR35/AtGLR2.5 positively, while BnGLR12/AtGLR1.2 and BnGLR53/AtGLR3.2 negatively, regulated plant resistance to S. sclerotiorum, indicating that GLR genes were differentially involved in this resistance. Our findings reveal the complex involvement of GLRs in B. napus resistance to S. sclerotiorum and provide clues for further functional characterization of BnGLRs.

Constitutive Overexpression of an NB-ARC Gene from Wild Chinese Vitis quinquangularis in Arabidopsis thaliana Enhances Resistance to Phytopathogenic Oomycete and Bacteria.

Resistance (R) genes were used to recognize pathogen effectors directly or indirectly in plants and activate defense signal pathways. Most of these R proteins consist of a nucleotide-binding adaptor (NB-ARC) domain, a leucine-rich repeat (LRR) domain and some also have a coiled-coil (CC) structure. In this study, we cloned a gene which encodes the CC-NB-ARC-LRR R protein (VqCNL) from Chinese wild grapevine Vitis. quinquangularis accession 'Dan-2'. The transcript of VqCNL was obviously induced by inoculation with Plasmopara viticola and the salicylic acid (SA) treatment. The results of sequence analysis showed that the VqCNL gene contained a CC domain at the N-terminus, along with an NB-ARC and an LRR domain at the C-terminus. We transferred this gene into wildtype Arabidopsis and treated transgenic lines with Hyaloperonospora arabidopsidis (Hpa) and Pseudomonas syringae pv. tomato DC3000 (Pst DC3000); the results demonstrated that VqCNL promotes broad spectrum resistance to pathogens. Furthermore, qPCR analysis displayed that VqCNL may display a significant function in disease resistance via activating SA signaling pathways. In general, these conclusions primarily demonstrated that VqCNL enhances the disease resistance level in plants and contributes to future research of the R gene identification for grape breeding biotechnology.

Physiological response of CmWRKY15-1 to chrysanthemum white rust based on TRV-VIGS.

Chrysanthemum White Rust (CWR) caused by Puccinia horiana Henn. is a major disease in the production process of chrysanthemum, which is widely spread all over the world and can be called "cancer" of chrysanthemum. To clarify the disease resistance function of disease resistance genes can provide a theoretical basis for the utilization and genetic improvement of chrysanthemum resistant varieties. In this study, the resistant cultivar 'China Red' was used as the experimental material. We constructed the silencing vector pTRV2-CmWRKY15-1 and obtained the silenced line named TRV-CmWRKY15-1. The results of enzyme activity after inoculation with pathogenic fungi showed that the activities of antioxidant enzymes SOD, POD, CAT and defense-related enzymes PAL and CHI in leaves were stimulated under the stress of P. horiana. In the WT, the activities of SOD, POD and CAT at the peak value were 1.99 times, 2.84 times and 1.39 times higher than that in TRV-CmWRKY15-1, respectively. And the activities of PALand CHI at the peak were 1.63 times and 1.12 times of TRV-CmWRKY15-1. The content of MDA and soluble sugar also confirmed that chrysanthemum was more susceptible to pathogenic fungi when CmWRKY15-1 was silenced. The expression levels of POD, SOD, PAL and CHI at different time points showed that the expressions of defense enzyme related genes were inhibited in TRV-WRKY15-1 under the infection of P. horiana, which weakened the ability of chrysanthemum to resist white rust. In conclusion, CmWRKY15-1 may increased the resistance of chrysanthemum to white rust by increasing the activity of protective enzyme system, which laid a foundation for breeding new varieties with disease resistance.

Identification and expression analysis of sugar transporter family genes reveal the role of ZmSTP2 and ZmSTP20 in maize disease resistance

Sugar is an indispensable source of energy for plant growth and development, and it requires the participation of sugar transporter proteins (STPs) for crossing the hydrophobic barrier in plants. Here, we systematically identified the genes encoding sugar transporters in the genome of maize (Zea mays L.), analyzed their expression patterns under different conditions, and determined their functions in disease resistance. The results showed that the mazie sugar transporter family contained 24 members, all of which were predicted to be distributed on the cell membrane and had a highly conserved transmembrane transport domain. The tissue-specific expression of the maize sugar transporter genes was analyzed, and the expression level of these genes was found to be significantly different in different tissues. The analysis of biotic and abiotic stress data showed that the expression levels of the sugar transporter genes changed significantly under different stress factors. The expression levels of ZmSTP2 and ZmSTP20 continued to increase following Fusarium graminearum infection. By performing disease resistance analysis of zmstp2 and zmstp20 mutants, we found that after inoculation with Cochliobolus carbonum, Setosphaeria turcica, Cochliobolus heterostrophus, and F. graminearum, the lesion area of the mutants was significantly higher than that of the wild-type B73 plant. In this study, the genes encoding sugar transporters in maize were systematically identified and analyzed at the whole genome level. The expression patterns of the sugar transporter-encoding genes in different tissues of maize and under biotic and abiotic stresses were revealed, which laid an important theoretical foundation for further elucidation of their functions.

Extra-large G proteins regulate disease resistance by directly coupling to immune receptors in Nicotiana benthamiana

Heterotrimeric G proteins, comprising Gα, Gβ, and Gγ subunits, are key regulators of eukaryotic intracellular signaling. Extra-large G (XLG) proteins are a subfamily of plant-specific Gα proteins interacting with plasma membrane-localized receptors to regulate multiple biological processes. The Nicotiana benthamiana genome encodes seven XLG proteins, NbXLG1–7, whose functions in disease resistance and underlying mechanisms are unknown. In this study, we silenced all the seven genes and found that disease susceptibility was enhanced when both NbXLG3 and NbXLG5 or NbXLG4 was silenced. Then, we generated N. benthamiana xlg3xlg5 double- and xlg4 single-mutant lines using the CRISPR-Cas9 approach. All the mutants showed reduced resistance to the bacterial pathogen Pseudomonas syringae pv. tomato DC3000, the fungal pathogen Sclerotinia sclerotiorum, and a series of oomycete pathogens, including Phytophthora capsici, Phytophthora infestans, and Phytophthora parasitica. We further demonstrated that NbXLG3/4/5 positively regulated microbial pattern-induced reactive oxygen species burst and defense gene expression by directly coupling to the tested plant immune receptors. In addition, we examined the role of NbXLG3/4/5 in abiotic stress tolerance and observed that NbXLG3 and NbXLG5 negatively regulated plant resistance to high-salt, mannitol, and PEG. Our study demonstrates the possible role of NbXLG3/4/5 in response to biotic and abiotic stresses and provides insights for the improvement of plant resistance to environmental changes.

The NF-Y Transcription Factor Family in Watermelon: Re-Characterization, Assembly of ClNF-Y Complexes, Hormone- and Pathogen-Inducible Expression and Putative Functions in Disease Resistance.

Nuclear factor Y (NF-Y) is a heterotrimeric transcription factor that binds to the CCAAT cis-element in the promoters of target genes and plays critical roles in plant growth, development, and stress responses. In the present study, we aimed to re-characterize the ClNF-Y family in watermelon, examine the assembly of ClNF-Y complexes, and explore their possible involvement in disease resistance. A total of 25 ClNF-Y genes (7 ClNF-YAs, 10 ClNF-YBs, and 8 ClNF-YCs) were identified in the watermelon genome. The ClNF-Y family was comprehensively characterized in terms of gene and protein structures, phylogenetic relationships, and evolution events. Different types of cis-elements responsible for plant growth and development, phytohormones, and/or stress responses were identified in the promoters of the ClNF-Y genes. ClNF-YAs and ClNF-YCs were mainly localized in the nucleus, while most of the ClNF-YBs were localized in the cytoplasm of cells. ClNF-YB5, -YB6, -YB7, -YB8, -YB9, and -YB10 interacted with ClNF-YC2, -YC3, -YC4, -YC5, -YC6, -YC7, and -YC8, while ClNF-YB1 and -YB3 interacted with ClNF-YC1. A total of 37 putative ClNF-Y complexes were identified, e.g., ClNF-YA1, -YA2, -YA3, and -YA7 assembled into 13, 8, 8, and 8 ClNF-Y complexes with different ClNF-YB/-YC heterodimers. Most of the ClNF-Y genes responded with distinct expression patterns to defense hormones such as salicylic acid, methyl jasmonate, abscisic acid, and ethylene precursor 1-aminocyclopropane-1-carboxylate, and to infection by the vascular infecting fungus Fusarium oxysporum f. sp. niveum. Overexpression of ClNF-YB1, -YB8, -YB9, ClNF-YC2, and -YC7 in transgenic Arabidopsis resulted in an earlier flowering phenotype. Overexpression of ClNF-YB8 in Arabidopsis led to enhanced resistance while overexpression of ClNF-YA2 and -YC2 resulted in decreased resistance against Botrytis cinerea. Similarly, overexpression of ClNF-YA3, -YB1, and -YC4 strengthened resistance while overexpression of ClNF-YA2 and -YB8 attenuated resistance against Pseudomonas syringae pv. tomato DC3000. The re-characterization of the ClNF-Y family provides a basis from which to investigate the biological functions of ClNF-Y genes in respect of growth, development, and stress response in watermelon, and the identification of the functions of some ClNF-Y genes in disease resistance enables further exploration of the molecular mechanism of ClNF-Ys in the regulation of watermelon immunity against diverse pathogens.

HvWRKY2 acts as an immunity suppressor and targets HvCEBiP to regulate powdery mildew resistance in barley

Plants use a sophisticated immune system to perceive pathogen infection and activate immune responses in a tightly controlled manner. In barley, HvWRKY2 acts as a repressor in barley disease resistance to the powdery mildew fungus, Blumeria graminis f. sp. hordei (Bgh). However, the molecular features of HvWRKY2 in its DNA-binding and repressor functions, as well as its target genes, are uncharacterized. We show that the W-box binding of HvWRKY2 requires an intact WRKY domain and an upstream sequence of ∼75 amino acids, and the HvWRKY2 W-box binding activity is linked to its repressor function in disease resistance. Chromatin immunoprecipitation (ChIP)-seq analysis identified HvCEBiP, a putative chitin receptor gene, as a target gene of HvWRKY2 in overexpressing transgenic barley plants. ChIP-qPCR and Electrophoretic Mobility Shift Assay (EMSA) verified the direct binding of HvWRKY2 to a W-box-containing sequence in the HvCEBiP promoter. HvCEBiP positively regulates resistance against Bgh in barley. Our findings suggest that HvWRKY2 represses barley basal immunity by directly targeting pathogen-associated molecular pattern (PAMP) recognition receptor genes, suggesting that HvCEBiP and likely chitin signaling function in barley PAMP-triggered immune responses to Bgh infection.

Genetic mapping and genomic prediction of sclerotinia stem rot resistance to rapeseed/canola (Brassica napus L.) at seedling stage.

GWAS detected ninety-eight significant SNPs associated with Sclerotinia sclerotiorum resistance. Six statistical models resulted in medium to high predictive ability, depending on trait, indicating potential of genomic prediction for disease resistance breeding. The lack of complete host resistance and a complex resistance inheritance nature between rapeseed/canola and Sclerotinia sclerotiorum often limits the development of functional molecular markers that enable breeding for sclerotinia stem rot (SSR) resistance. However, genomics-assisted selection has the potential to accelerate the breeding for SSR resistance. Therefore, genome-wide association (GWA) mapping and genomic prediction (GP) were performed using a diverse panel of 337 rapeseed/canola genotypes. Three-week-old seedlings were screened using the petiole inoculation technique (PIT). Days to wilt (DW) up to 2weeks and lesion phenotypes (LP) at 3, 4, and 7days post-inoculation (dpi) were recorded. A strong correlation (r = - 0.90) between DW and LP_4dpi implied that a single time point scoring at four days could be used as a proxy trait. GWA analyses using single-locus (SL) and multi-locus (ML) models identified a total of 41, and 208 significantly associated SNPs, respectively. Out of these, ninety-eight SNPs were identified by a combination of the SL model and any of the ML models, at least two ML models, or two traits. These SNPs explained 1.25-12.22% of the phenotypic variance and considered as significant, could be associated with SSR resistance. Eighty-three candidate genes with a function in disease resistance were associated with the significant SNPs. Six GP models resulted in moderate to high (0.42-0.67) predictive ability depending on SSR resistance traits. The resistant genotypes and significant SNPs will serve as valuable resources for future SSR resistance breeding. Our results also highlight the potential of genomic selection to improve rapeseed/canola breeding for SSR resistance.

An experimental test of disease resistance function in the skin-associated bacterial communities of three tropical amphibian species.

Variation in the structure of host-associated microbial communities has been correlated with the occurrence and severity of disease in diverse host taxa, suggesting a key role of the microbiome in pathogen defense. However, whether these correlations are typically a cause or consequence of pathogen exposure remains an open question, and requires experimental approaches to disentangle. In amphibians, infection by the fungal pathogen Batrachochytrium dendrobatidis (Bd) alters the skin microbial community in some host species, whereas in other species, the skin microbial community appears to mediate infection dynamics. In this study, we completed experimental Bd exposures in three species of tropical frogs (Agalychnis callidryas, Dendropsophus ebraccatus,andCraugastor fitzingeri) that were sympatric with Bd at the time of the study. For all three species, we identified key taxa within the skin bacterial communities that were linked to Bd infection dynamics. We also measured higher Bd infection intensities in D. ebraccatus and C. fitzingeri that were associated with higher mortality in C. fitzingeri. Our findings indicate that microbially mediated pathogen resistance is a complex trait that can vary within and across host species, and suggest that symbiont communities that have experienced prior selection for defensive microbes may be less likely to be disturbed by pathogen exposure.

Candidate resistance genes to foliar phylloxera identified at Rdv3 of hybrid grape.

The foliage of the native grape species Vitis riparia and certain cold-hardy hybrid grapes are particularly susceptible to the insect pest phylloxera, Daktulosphaira vitifoliae Fitch. A previous study using a cold-hardy hybrid grape biparental F1 population (N ~ 125) detected the first quantitative trait locus (QTL) for foliar resistance on chromosome 14, designated as resistance to Daktulosphaira vitifoliae 3 (Rdv3). This locus spans a ~ 7-Mbp (10–20 cM) region and is too wide for effective marker-assisted selection or identification of candidate genes. Therefore, we fine mapped the QTL using a larger F1 population, GE1783 (N ~ 1023), and genome-wide rhAmpSeq haplotype markers. Through three selective phenotyping experiments replicated in the greenhouse, we screened 184 potential recombinants of GE1783 using a 0 to 7 severity rating scale among other phylloxera severity traits. A 500-kb fine mapped region at 4.8 Mbp on chromosome 14 was identified. The tightly linked rhAmpSeq marker 14_4 805 213 and flanking markers can be used for future marker-assisted breeding. This region contains 36 candidate genes with predicted functions in disease resistance (R genes and Bonzai genes) and gall formation (bifunctional 3-dehydroquinate dehydratase/shikimate dehydrogenase). Disease resistance genes suggest a traditional R-gene-mediated resistance mechanism often accompanied by a hypersensitive response, which has been widely studied in the plant pathology field. A novel resistance mechanism, non-responsiveness to phylloxera gall formation is proposed as a function of the bifunctional dehydratase gene, which plays a role in gallic acid biosynthesis and is important in gall formation. This study has implications for improvement of foliar phylloxera resistance in cold-hardy hybrid germplasm and is a starting place to understand the mechanism of resistance in crops to gall-forming insects.

MicroRNA482/2118, a miRNA superfamily essential for both disease resistance and plant development.

MicroRNAs (miRNAs) are a class of 21-24 nucleotides (nt) noncoding small RNAs ubiquitously distributed across the plant kingdom. miR482/2118, one of the conserved miRNA superfamilies originating from gymnosperms, has divergent main functions in core-angiosperms. It mainly regulates NUCLEOTIDE BINDING SITE-LEUCINE-RICH REPEAT (NBS-LRR) genes in eudicots, functioning as an essential component in plant disease resistance; in contrast, it predominantly targets numerous long noncoding RNAs (lncRNAs) in monocot grasses, which are vital for plant reproduction. Usually, miR482/2118 is 22-nt in length, which can trigger the production of phased small interfering RNAs (phasiRNAs) after directed cleavage. PhasiRNAs instigated from target genes of miR482/2118 enhance their roles in corresponding biological processes by cis-regulation on cognate genes and expands their function to other pathways via trans activity on different genes. This review summarizes the origin, biogenesis, conservation, and evolutionary characteristics of the miR482/2118 superfamily and delineates its diverse functions in disease resistance, plant development, stress responses, etc.

Identification and expression assay of calcium-dependent protein kinase family genes in Hevea brasiliensis and determination of HbCDPK5 functions in disease resistance

Calcium (Ca2+) signaling is one of the earliest factors to coordinate plant adaptive responses. As direct sensors and activators of Ca2+ signals, calcium-dependent protein kinases (CDPKs) were reported to be widely involved in regulating different biotic and abiotic stress stimuli. In this study, 32 Hevea brasiliensis CDPK (HbCDPK) genes were predicted and classified into four subgroups. Among them, the full-length coding sequences of 28 HbCDPK genes were confirmed by RT-PCR and verified by sequencing. Putative cis-elements assay in the promoters of HbCDPKs showed that most of the HbCDPK genes contained gibberellic acid-responsive element (GARE), abscisic acid-responsive element (ABRE), salicylic acid-responsive element (SARE), defense and stress responsive element (TC-rich repeats) and low-temperature response element (LTR), which could be activated by different biotic and abiotic stresses. Real-time PCR analysis indicated that 28 HbCDPK genes respond to infection of pathogenic fungi and a variety of phytohormones. Subcellular localization was observed with most HbCDPKs located in cell membrane, cytoplasm or organelles. Some HbCDPKs were confirmed to cause reactive oxygen species (ROS) production and accumulation in rubber tree mesophyll protoplast directly. HbCDPK5 was strongly induced by the inoculation with Colletotrichum gloeosporioides and was chosen for further analysis. HbCDPK5 localized to the cell membrane and cytoplasm, and obviously regulated the accumulation of ROS in rubber tree mesophyll protoplast. Overexpression of HbCDPK5 in Arabidopsis enhanced the resistance to Botrytis cinerea. These results indicate that rubber tree CDPK genes play important roles in plant disease resistance.

A simplified synthetic community rescues Astragalus mongholicus from root rot disease by activating plant-induced systemic resistance

BackgroundPlant health and growth are negatively affected by pathogen invasion; however, plants can dynamically modulate their rhizosphere microbiome and adapt to such biotic stresses. Although plant-recruited protective microbes can be assembled into synthetic communities for application in the control of plant disease, rhizosphere microbial communities commonly contain some taxa at low abundance. The roles of low-abundance microbes in synthetic communities remain unclear; it is also unclear whether all the microbes enriched by plants can enhance host adaptation to the environment. Here, we assembled a synthetic community with a disease resistance function based on differential analysis of root-associated bacterial community composition. We further simplified the synthetic community and investigated the roles of low-abundance bacteria in the control of Astragalus mongholicus root rot disease by a simple synthetic community.ResultsFusarium oxysporum infection reduced bacterial Shannon diversity and significantly affected the bacterial community composition in the rhizosphere and roots of Astragalus mongholicus. Under fungal pathogen challenge, Astragalus mongholicus recruited some beneficial bacteria such as Stenotrophomonas, Achromobacter, Pseudomonas, and Flavobacterium to the rhizosphere and roots. We constructed a disease-resistant bacterial community containing 10 high- and three low-abundance bacteria enriched in diseased roots. After the joint selection of plants and pathogens, the complex synthetic community was further simplified into a four-species community composed of three high-abundance bacteria (Stenotrophomonas sp., Rhizobium sp., Ochrobactrum sp.) and one low-abundance bacterium (Advenella sp.). Notably, a simple community containing these four strains and a thirteen-species community had similar effects on the control root rot disease. Furthermore, the simple community protected plants via a synergistic effect of highly abundant bacteria inhibiting fungal pathogen growth and less abundant bacteria activating plant-induced systemic resistance.ConclusionsOur findings suggest that bacteria with low abundance play an important role in synthetic communities and that only a few bacterial taxa enriched in diseased roots are associated with disease resistance. Therefore, the construction and simplification of synthetic communities found in the present study could be a strategy employed by plants to adapt to environmental stress.-VujMZjCpFzTumqS8Rf9nHVideo abstract

WIPK-NtLTP4 pathway confers resistance to Ralstonia solanacearum in tobacco.

WIPK-NtLTP4 module improves the resistance to R. solanacearum via upregulating the expression of defense-related genes, increasing the antioxidant enzyme activity, and promoting stomatal closure in tobacco. Lipid transfer proteins (LTPs) are a class of small lipid binding proteins that play important roles in biotic and abiotic stresses. The previous study revealed that NtLTP4 positively regulates salt and drought stresses in Nicotiana tabacum. However, the role of NtLTP4 in biotic stress, especially regarding its function in disease resistance remains unclear. Here, the critical role of NtLTP4 in regulating resistance to Ralstonia solanacearum (R. solanacearum), a causal agent of bacterial wilt disease in tobacco, was reported. The NtLTP4-overexpressing lines markedly improved the resistance to R. solanacearum by upregulating the expression of defense-related genes, increasing the antioxidant enzyme activity, and promoting stomatal closure. Moreover, NtLTP4 interacted with wound-induced protein kinase (WIPK; a homolog of MAPK3 in tobacco) and acted in a genetically epistatic manner to WIPK in planta. WIPK could directly phosphorylate NtLTP4 to positively regulate its protein abundance. Taken together, these results broaden the knowledge about the functions of the WIPK-NtLTP4 module in disease resistance and may provide valuable information for improving tobacco plant tolerance to R. solanacearum.

Introgression among North American wild grapes (Vitis) fuels biotic and abiotic adaptation

BackgroundIntrogressive hybridization can reassort genetic variants into beneficial combinations, permitting adaptation to new ecological niches. To evaluate evolutionary patterns and dynamics that contribute to introgression, we investigate six wild Vitis species that are native to the Southwestern United States and useful for breeding grapevine (V. vinifera) rootstocks.ResultsBy creating a reference genome assembly from one wild species, V. arizonica, and by resequencing 130 accessions, we focus on identifying putatively introgressed regions (pIRs) between species. We find six species pairs with signals of introgression between them, comprising up to ~ 8% of the extant genome for some pairs. The pIRs tend to be gene poor, located in regions of high recombination and enriched for genes implicated in disease resistance functions. To assess potential pIR function, we explore SNP associations to bioclimatic variables and to bacterial levels after infection with the causative agent of Pierce’s disease (Xylella fastidiosa). pIRs are enriched for SNPs associated with both climate and bacterial levels, suggesting that introgression is driven by adaptation to biotic and abiotic stressors.ConclusionsAltogether, this study yields insights into the genomic extent of introgression, potential pressures that shape adaptive introgression, and the evolutionary history of economically important wild relatives of a critical crop.

Regulation of cytoskeleton-associated protein activities: Linking cellular signals to plant cytoskeletal function.

The plant cytoskeleton undergoes dynamic remodeling in response to diverse developmental and environmental cues. Remodeling of the cytoskeleton coordinates growth in plant cells, including trafficking and exocytosis of membrane and wall components during cell expansion, and regulation of hypocotyl elongation in response to light. Cytoskeletal remodeling also has key functions in disease resistance and abiotic stress responses. Many stimuli result in altered activity of cytoskeleton-associated proteins, microtubule-associated proteins (MAPs) and actin-binding proteins (ABPs). MAPs and ABPs are the main players determining the spatiotemporally dynamic nature of the cytoskeleton, functioning in a sensory hub that decodes signals to modulate plant cytoskeletal behavior. Moreover, MAP and ABP activities and levels are precisely regulated during development and environmental responses, but our understanding of this process remains limited. In this review, we summarize the evidence linking multiple signaling pathways, MAP and ABP activities and levels, and cytoskeletal rearrangements in plant cells. We highlight advances in elucidating the multiple mechanisms that regulate MAP and ABP activities and levels, including calcium and calmodulin signaling, ROP GTPase activity, phospholipid signaling, and post-translational modifications.