Transcriptomic profiling of Brassica napus responses to Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic bacterial pathogen of plants. Unlike the well-characterized plant defense responses to highly adapted bacterial phytopathogens, little is known about plant response to P. aeruginosa infection. In this study, we examined the Brassica napus (canola) tissue-specific response to P. aeruginosa infection using RNA sequencing. Transcriptomic analysis of canola seedlings over a 5 day P. aeruginosa infection revealed that many molecular processes involved in plant innate immunity were up-regulated, whereas photosynthesis was down-regulated. Phytohormones control many vital biological processes within plants, including growth and development, senescence, seed setting, fruit ripening, and innate immunity. The three main phytohormones involved in plant innate immunity are salicylic acid (SA), jasmonic acid (JA), and ethylene (ET). Many bacterial pathogens have evolved multiple strategies to manipulate these hormone responses in order to infect plants successfully. Interestingly, gene expression within all three phytohormone (SA, JA, and ET) signaling pathways was up-regulated in response to P. aeruginosa infection. This study identified a unique plant hormone response to the opportunistic bacterial pathogen P. aeruginosa infection.

Download Full-text

All Hands on Deck—The Role of Chloroplasts, Endoplasmic Reticulum, and the Nucleus in Driving Plant Innate Immunity

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-05-10-0113 ◽

2010 ◽

Vol 23 (11) ◽

pp. 1368-1380 ◽

Cited By ~ 55

Author(s):

Meenu S. Padmanabhan ◽

S. P. Dinesh-Kumar

Keyword(s):

Innate Immunity ◽

Endoplasmic Reticulum ◽

Second Messengers ◽

Defense Responses ◽

Plant Innate Immunity ◽

Er Quality Control ◽

Immune Modulators ◽

Immune Receptors ◽

Cytoplasmic Transport

Plant innate immunity is mediated by cell membrane and intracellular immune receptors that function in distinct and overlapping cell-signaling pathways to activate defense responses. It is becoming increasingly evident that immune receptors rely on components from multiple organelles for the generation of appropriate defense responses. This review analyzes the defense-related functions of the chloroplast, nucleus, and endoplasmic reticulum (ER) during plant innate immunity. It details the role of the chloroplasts in synthesizing defense-specific second messengers and discusses the retrograde signal transduction pathways that exist between the chloroplast and nucleus. Because the activities of immune modulators are regulated, in part, by their subcellular localization, the review places special emphasis on the dynamics and nuclear–cytoplasmic transport of immune receptors and regulators and highlights the importance of this process in generating orderly events during an innate immune response. The review also covers the recently discovered contributions of the ER quality-control pathways in ensuring the signaling competency of cell surface immune receptors or immune regulators.

Download Full-text

Sublethal Heavy Metal Stress Stimulates Innate Immunity in Tomato

The Scientific World JOURNAL ◽

10.1155/2015/208649 ◽

2015 ◽

Vol 2015 ◽

pp. 1-7 ◽

Cited By ~ 12

Author(s):

Nilanjan Chakraborty ◽

Swarnendu Chandra ◽

Krishnendu Acharya

Keyword(s):

Heavy Metal ◽

Innate Immunity ◽

Heavy Metal Stress ◽

Defense Responses ◽

Spectrophotometric Analysis ◽

Metal Stress ◽

Sublethal Dose ◽

No Production ◽

Plant Defense Responses

Effect of sublethal heavy metal stress as plant biotic elicitor for triggering innate immunity in tomato plant was investigated. Copper inin vivocondition induced accumulation of defense enzymes like peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL), andβ-1,3 glucanase along with higher accumulation of total phenol, antioxidative enzymes (catalase and ascorbate peroxidase), and total chlorophyll content. Furthermore, the treatment also induced nitric oxide (NO) production which was confirmed by realtime visualization of NO burst using a fluorescent probe 4,5-diaminofluorescein diacetate (DAF-2DA) and spectrophotometric analysis. The result suggested that the sublethal dose of heavy metal can induce an array of plant defense responses that lead to the improvement of innate immunity in plants.

Download Full-text

Down Regulation of Virulence Factors of Pseudomonas aeruginosa by Salicylic Acid Attenuates Its Virulence on Arabidopsis thaliana and Caenorhabditis elegans

Infection and Immunity ◽

10.1128/iai.73.9.5319-5328.2005 ◽

2005 ◽

Vol 73 (9) ◽

pp. 5319-5328 ◽

Cited By ~ 121

Author(s):

B. Prithiviraj ◽

H. P. Bais ◽

T. Weir ◽

B. Suresh ◽

E. H. Najarro ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Arabidopsis Thaliana ◽

Salicylic Acid ◽

Plant Defense ◽

Virulence Factors ◽

Target Genes ◽

Defense Responses ◽

Infection Model ◽

Plant Defense Responses ◽

Wild Type

ABSTRACT Salicylic acid (SA) is a phenolic metabolite produced by plants and is known to play an important role in several physiological processes, such as the induction of plant defense responses against pathogen attack. Here, using the Arabidopsis thaliana-Pseudomonas aeruginosa pathosystem, we provide evidence that SA acts directly on the pathogen, down regulating fitness and virulence factor production of the bacteria. Pseudomonas aeruginosa PA14 showed reduced attachment and biofilm formation on the roots of the Arabidopsis mutants lox2 and cpr5-2, which produce elevated amounts of SA, as well as on wild-type Arabidopsis plants primed with exogenous SA, a treatment known to enhance endogenous SA concentration. Salicylic acid at a concentration that did not inhibit PA14 growth was sufficient to significantly affect the ability of the bacteria to attach and form biofilm communities on abiotic surfaces. Furthermore, SA down regulated three known virulence factors of PA14: pyocyanin, protease, and elastase. Interestingly, P. aeruginosa produced more pyocyanin when infiltrated into leaves of the Arabidopsis transgenic line NahG, which accumulates less SA than wild-type plants. This finding suggests that endogenous SA plays a role in down regulating the synthesis and secretion of pyocyanin in vivo. To further test if SA directly affects the virulence of P. aeruginosa, we used the Caenorhabiditis elegans-P. aeruginosa infection model. The addition of SA to P. aeruginosa lawns significantly diminished the bacterium's ability to kill the worms, without affecting the accumulation of bacteria inside the nematodes' guts, suggesting that SA negatively affects factors that influence the virulence of P. aeruginosa. We employed microarray technology to identify SA target genes. These analyses showed that SA treatment affected expression of 331 genes. It selectively repressed transcription of exoproteins and other virulence factors, while it had no effect on expression of housekeeping genes. Our results indicate that in addition to its role as a signal molecule in plant defense responses, SA works as an anti-infective compound by affecting the physiology of P. aeruginosa and ultimately attenuating its virulence.

Download Full-text

Potato Lipoxygenase POTLX-3 Gene is Expressed In Response to Pathogens but Not Wounding

HortScience ◽

10.21273/hortsci.33.3.499c ◽

1998 ◽

Vol 33 (3) ◽

pp. 499c-499

Author(s):

Mikhailo V. Kolomiets ◽

Richard J. Gladon ◽

David J. Hannapel

Keyword(s):

Methyl Jasmonate ◽

Pseudomonas Syringae ◽

Defense Mechanisms ◽

Active Oxygen Species ◽

Bacterial Pathogen ◽

Defense Responses ◽

Specific Response ◽

Visual Appearance ◽

Resistant Lines ◽

Volatile Aldehydes

Lipoxygenases are the first committed enzymes in biosynthetic pathways that produce jasmonic acid, methyl jasmonate, traumatin, fatty acid hydroperoxides, and volatile aldehydes. These pathways often function in growth- and defense-related processes in plants. Products of lipoxygenases may be the primary cause of the hypersensitive response (HR) because lipoxygenase by-products such as organic free radicals and active oxygen species are involved in cell membrane degradation during resistance responses against pathogens. In order to study lipoxygenase involvement in defense responses against pathogens, we have isolated and characterized a potato lipoxygenase gene that we have designated POTLX-3. POTLX-3 is not expressed in any potato organs, is not induced by wounding, but is strongly induced in leaves treated with ethylene, methyl jasmonate, or inoculum of Phytophthora infestans, the causal agent of potato late blight. In response to infection, POTLX-3 transcripts accumulate more rapidly in resistant lines than in susceptible lines. In resistant lines, the greatest amount of induction preceded the visual appearance of localized necrotic lesions, consistent with possible involvement of POTLX-3 in HR development. Expression of POTLX-3 also is activated in response to inoculation with the bacterial pathogen Pseudomonas syringae pv. phaseolicola, which causes strongly expressed HR in all potato cultivars. Thus, POTLX-3 expression is not a specific response to P. infestans, but rather a common response related to HR development against a broad range of pathogens. Pattern of POTLX-3 expression indicates that it may have a specific role in defense mechanisms against pathogens.

Download Full-text

Ocimum sanctum, OscWRKY1, regulates phenylpropanoid pathway genes and promotes resistance to pathogen infection in Arabidopsis

10.1101/2022.01.12.474522 ◽

2022 ◽

Author(s):

Ashutosh Joshi ◽

Gajendra Singh Jeena ◽

Shikha ◽

Ravi Kumar ◽

Alok Pandey ◽

...

Keyword(s):

Pseudomonas Syringae ◽

Bacterial Pathogen ◽

Defense Responses ◽

Phenylpropanoid Pathway ◽

Wrky Transcription Factor ◽

Ocimum Sanctum ◽

Plant Defense Responses ◽

Cis Element ◽

Pal Activity ◽

Direct Regulation

WRKY transcription factor (TF) family regulates various developmental and physiological functions in plants. PAL genes encode enzymes which are involved in plant defense responses, but the direct regulation of PAL genes and phenylpropanoid pathway through WRKY TF is not well characterized. In the present study, we have characterized an OscWRKY1 gene from O. sanctum which shows induced expression after methyl jasmonate (MeJA), salicylic acid (SA), and wounding. Recombinant OscWRKY1 protein binds to the W-box cis-element TTGAC[C/T] and activates the reporter gene in yeast. Overexpression of OscWRKY1 enhances Arabidopsis resistance towards Pseudomonas syringae pv. tomato Pst DC3000. Upstream activator sequences of PAL and C4H have identified the conserved W-box cis-element (TTGACC) in both O. sanctum and Arabidopsis. OscWRKY1 was found to interact with W-box cis-element present in the PAL and C4H promoters. Silencing of OscWRKY1 using VIGS resulted in reduced expression of PAL, C4H, COMT, F5H and 4CL transcripts. OscWRKY1 silenced plants exhibit reduced PAL activity, whereas, the overexpression lines of OscWRKY1 in Arabidopsis exhibit increased PAL activity. These results revealed that OscWRKY1 positively regulates the phenylpropanoid pathway genes and enhances the resistance against bacterial pathogen in Arabidopsis.

Download Full-text

Isolation of Arabidopsis Mutants With Enhanced Disease Susceptibility by Direct Screening

Genetics ◽

10.1093/genetics/143.2.973 ◽

1996 ◽

Vol 143 (2) ◽

pp. 973-982 ◽

Cited By ~ 17

Author(s):

Jane Glazebrook ◽

Elizabeth E Rogers ◽

Frederick M Ausubel

Keyword(s):

Plant Defense ◽

Pseudomonas Syringae ◽

Disease Susceptibility ◽

Bacterial Pathogen ◽

Defense Responses ◽

Screening Strategy ◽

Genetic Dissection ◽

Plant Defense Responses ◽

Defense Genes ◽

Increased Susceptibility

Abstract To discover which components of plant defense responses make significant contributions to limiting pathogen attack, we screened a mutagenized population of Arabidopsis thalzana for individuals that exhibit increased susceptibility to the moderately virulent bacterial pathogen Pseudomonas syringae pv. maculicola ES4326 (Psm ES4326). The 12 enhanced disease susceptibility (eds) mutants isolated included alleles of two genes involved in phytoalexin biosynthesis (pad2, which had been identified previously, and pad4, which had not been identified previously), two alleles of the previously identified npr1 gene, which affects expression of other defense genes, and alleles of seven previously unidentified genes of unknown function. The npr-1 mutations caused greatly reduced expression of the PRI gene in response to PsmES4326 infection, but had little effect on expression of two other defense genes, BGL2 and PR5, suggesting that PR1 expression may be important for limiting growth of PsmES4326. While direct screens for mutants with quantitative pathogen-susceptibility phenotypes have not been reported previously, our finding that mutants isolated in this way include those affected in known defense responses supports the notion that this type of screening strategy allows genetic dissection of the roles of various plant defense responses in disease resistance.

Download Full-text