Isolation and characterization of NgRLK1, a receptor-like kinase of Nicotiana glutinosa that interacts with the elicitin of Phytophthora capsici

Elicitins, extracellular proteins from Phytophthora fungi, elicit a hypersensitivity response (HR), including systemic acquired resistance, in some plants. The elicitin capsicein (~10 kDa) was purified by FPLC from culture filtrates of P. capsici. Purified native and recombinant capsicein induced a hypersensitive response in leaves of the non-host plants Nicotiana glutinosa and Brassica rapa subsp. pekinensis. To search for candidate capsicein-interacting proteins from N. glutinosa, a yeast two-hybrid assay was used. We identified a protein interactor that is homologous to a serine/threonine kinase of the plant receptor-like kinase (RLK) group and designated it NgRLK1. The ORF of NgRLK1 encodes a polypeptide of 832 amino acids (93,490 Da). A conserved domain analysis revealed that NgRLK1 has structural features typical of a plant RLK. NgRLK1 was autophosphorylated, with higher activity in the presence of Mn2+ than Mg2+

In silico identification of coffee genome expressed sequences potentially associated with resistance to diseases

Sequences potentially associated with coffee resistance to diseases were identified by in silico analyses using the database of the Brazilian Coffee Genome Project (BCGP). Keywords corresponding to plant resistance mechanisms to pathogens identified in the literature were used as baits for data mining. Expressed sequence tags (ESTs) related to each of these keywords were identified with tools available in the BCGP bioinformatics platform. A total of 11,300 ESTs were mined. These ESTs were clustered and formed 979 EST-contigs with similarities to chitinases, kinases, cytochrome P450 and nucleotide binding site-leucine rich repeat (NBS-LRR) proteins, as well as with proteins related to disease resistance, pathogenesis, hypersensitivity response (HR) and plant defense responses to diseases. The 140 EST-contigs identified through the keyword NBS-LRR were classified according to function. This classification allowed association of the predicted products of EST-contigs with biological processes, including host defense and apoptosis, and with molecular functions such as nucleotide binding and signal transducer activity. Fisher's exact test was used to examine the significance of differences in contig expression between libraries representing the responses to biotic stress challenges and other libraries from the BCGP. This analysis revealed seven contigs highly similar to catalase, chitinase, protein with a BURP domain and unknown proteins. The involvement of these coffee proteins in plant responses to disease is discussed

PpCRN7 and PpCRN20 of phythophthora parasitica regulate plant cell death leading to enhancement of host susceptibility

Phytophthora species secrete cytoplasmic effectors from a family named Crinkler (CRN), which are characterised by the presence of conserved specific domains in the N- and C-terminal regions. P. parasitica causes disease in a wide range of host plants, however the role of CRN effectors in these interactions remains unclear. Here, we aimed to: (i) identify candidate CRN encoding genes in P. parasitica genomes; (ii) evaluate the transcriptional expression of PpCRN (Phytophthora parasitica Crinkler candidate) during the P. parasitica interaction with Citrus sunki (high susceptible) and Poncirus trifoliata (resistant); and (iii) functionally characterize two PpCRNs in the model plant Nicotiana benthamiana. Results Our in silico analyses identified 80 putative PpCRN effectors in the genome of P. parasitica isolate 'IAC 01/95.1'. Transcriptional analysis revealed differential gene expression of 20 PpCRN candidates during the interaction with the susceptible Citrus sunki and the resistant Poncirus trifoliata. We have also found that P. parasitica is able to recognize different citrus hosts and accordingly modulates PpCRNs expression. Additionally, two PpCRN effectors, namely PpCRN7 and PpCRN20, were further characterized via transient gene expression in N. benthamiana leaves. The elicitin INF-1-induced Hypersensitivity Response (HR) was increased by an additive effect driven by PpCRN7 expression, whereas PpCRN20 expression suppressed HR response in N. benthamiana leaves. Despite contrasting functions related to HR, both effectors increased the susceptibility of plants to P. parasitica. Conclusions PpCRN7 and PpCRN20 have the ability to increase P. parasitica pathogenicity and may play important roles at different stages of infection. These PpCRN-associated mechanisms are now targets of biotechnological studies aiming to break pathogen's virulence and to promote plant resistance19CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ445390/2014–0; 465440/2014–

Identificação e patogenicidade de Pseudomonas cichorii associada ao crestamento bacteriano da gérbera no Distrito Federal

Em 2013, amostras foliares de plantas de gérbera, apresentando sintomas de crestamento, foram coletadas em telados de cultivo de corte, no núcleo rural alexandre gusmão, localizado em brazlândia-df. sete isolados bacterianos obtidos foram submetidos à caracterização fenotípica e molecular, incluindo testes de patogenicidade, testes lopat e sequenciamento parcial do gene 16s rdna. todos os isolados foram gram-negativos, aeróbios, oxidase positivos, produziram pigmento fluorescente, induziram reação de hipersensibilidade em folhas de fumo, utilizaram sorbitol e glutamato, e foram patogênicos a 24 diferentes espécies de plantas. os resultados destes testes e análises de sequências do rdna mostraram 100% de identidade com pseudomonas cichorii. para o nosso conhecimento, este é o primeiro relato de p. cichorii, em gérbera, no distrito federal.In 2013, leaf samples of gerbera plants showing symptoms of bacterial blight were collected in cut-flower high tunnels, in the settlement of núcleo rural alexandre gusmão, located in brazlândia, distrito federal, brazil. seven isolates obtained were subjected to phenotypic and molecular characterization, including pathogenicity tests, lopat, and partial sequencing of the 16s rdna gene. all isolates were gram-negative, aerobic, oxidase-positive, produced fluorescent pigment, induced hypersensitivity in tobacco leaves, used sorbitol and glutamate and were pathogenic to 24 different plant species. results of these tests and analysis of the sequences of rdna showed 100% identity with pseudomonas cichorii. to our knowledge, this is the first report of p. cichorii in gerbera in the federal district

Reactive oxygen species and cellular interactions between Mycosphaerella fijiensis and banana.

Globally, the banana plant (Musa spp) is the fourth most important crop after rice, wheat and corn (based on production in tons). It is cultivated in more than 100 tropical and subtropical countries, mainly by small producers and is a fundamental food source for millions of people. Black leaf streak disease (BLSD), caused by Mycosphaerella fijiensis Morelet (sexual phase) or Paracercospora fijiensis (Morelet) Deighton (asexual phase), is the main disease affecting the world's banana culture. This disease has a wide geographical distribution accounting for losses exceeding 50% of global banana production. We conducted a comparative histocytological study on the kinetics of the infection process using three banana genotypes with phenotypes that differ in resistance to BLSD: Grand Naine (Susceptible), Pisang Madu (Partially Resistant) and Calcutta 4 (Resistant). Experiments were conducted under controlled conditions with the objective of characterizing the cellular interaction processes between M. fijiensis and Musa acuminata. Conidia germination occurred 24 hours after inoculation. Germination rates were high (97%) and there were no significant differences between the three genotypes (P>0.147). The Peroxidase enzyme and H2O2 were associated with a hypersensitivity-like reaction in the resistant genotype Calcutta 4, indicating a possible role of the enzyme or its product as defense mechanisms against M. fijiensis in banana plants

Crude Oil Biodegradation Potential using Acinetobacter baumannii CYA20 and Bacillus subtilis CYA27 from the Bekasi Coast, Indonesia

The pollution of coastal areas caused by oil spills is an environmental issue that needs further attention. Crude oil contains persistent organic pollutants (POPs) that are difficult to degrade. This study aimed to isolate bacterial strains capable of degrading crude oil from the Bekasi coast through bacterial isolate characterization and crude oil biodegradation tests using a crude oil-enriched microcosm model. Two strains with higher TPH degradation values were selected among the isolated bacteria, namely CYA20 and CYA27, which specifically showed values of 46% and 66%, respectively. These strains were tolerant to NaCl concentrations of up to 4% and 12%, respectively, and they were also tolerant to pH values ranging from 5 to 9 and temperatures between 10°C and 50°C.  Both strains were shown to utilize POPs, such as phenanthrene and fluorene, produce biosurfactants, and exhibited an emulsification activity in paraffin ranging from 0.373 to 0.533. Phylogenetic analyses identified these bacterial strains as Acinetobacter baumannii CYA20 and Bacillus subtilis CYA27, respectively. The results of this study indicate that these isolates could be developed as biodegradation agents for the bioremediation of crude oil-contaminated environments

Induced resistance during the interaction pathogen x plant and the use of resistance inducers

Plants react to aggressions through different defence responses. Mechanical barriers consist in the increase of production and deposition of substances capable of containing pathogen invasion. Chemical barriers consist in the increase of concentration or activity of defence proteins and synthesis of phenolic compounds and phytoalexins. Elicitor substances have been widely used in plant disease control showing impressive results and a low impact to the environment and man. This review contains information about plant defence mechanisms and shows the use of inducers of resistance in the control of pathogens and prospects of advance towards sustainable agriculture

P61 protein of Citrus Leprosis Virus C elicits an hypersensitive-like response in Nicotiana Benthamiana.

Citrus leprosis virus C (CiLV-C, genus Cilevirus, family Kitaviridae) is the prevalent causal agent of citrus leprosis, the main viral disease affecting citrus groves in Brazil. [...]

Histological comparisons of needle tissues of four species of white pine infected by Cronartium ribicola

Hypersensitive response-like (HR-like) needle reactions to infection by the white pine blister rust pathogen, Cronartium ribicola, have been reported for several species of five needle pines native to western North America. The best-studied examples are in Pinus monticola and P. lambertiana. In these species a "needle spot" phenotype has been identified in which HR-like needle reactions are related to disease resistance that is conditioned by a major gene. Conventionally it is believed that the HR-like needle reactions in resistant pines prevent spread of the pathogen to vascular stem tissue by HR mechanisms commonly seen in other plant-pathogen incompatibility interactions, i.e. a rapidly induced plant cell death and subsequent localized tissue necrosis. The dead cells present a barrier to colonization by biotrophic pathogens and cause degeneration of fungal hyphae preventing further pathogen colonization. Structural analyses of early C. ribicola needle colonization in resistant Pinus spp. have shown, however, that these symptoms and their underlying physiology are fundamentally different from the clearly defined HR described in other host-pathogen systems. Contrary to the pattern of HR responses seen in most incompatible host reactions, onset of needle lesions was first seen several weeks after initial entry of C. ribicola. We observed extensive proliferation of fungal hyphae in the host and penetration of the needle endodermis and vascular tissue by the pathogen prior to the onset of a discernable HR or cell necrosis. The amount of fungal tissue present and progress of needle colonization was similar for both resistant and susceptible Pinus spp. Therefore, typical HR does not appear to function in needles as the mechanism of disease resistance in the "needle reaction" phenotype