A novel Sec14 phospholipid transfer protein from Nicotiana benthamiana is up-regulated in response to Ralstonia solanacearum infection, pathogen associated molecular patterns and effector molecules and involved in plant immunity

To elucidate the molecular mechanisms of plant immune responses, we isolated genes whose expression was regulated by inoculation with Ralstonia solanacearum. Here, we report the characterization of Nicotiana benthamiana belonging to the SEC14-gene superfamily designated as Nicotiana benthamiana SEC14 (NbSEC14). NbSEC14 rescued growth defects and impaired invertase secretion associated with the yeast sec14p temperature-sensitive mutant, while recombinant NbSec14 protein had phospholipids transfer activity. NbSEC14 expression was up-regulated in N. benthamiana leaves after inoculation with virulent or avirulent R. solanacearum. Expression of NbSEC14 was induced by treatment with chitin, flg22, and by Agrobacterium-mediated transient expression of INF1 elicitin, AvrA from R. solanacearum, and co-expression of the capsid protein from Tobacco mild green mosaic virus with its cognate resistance L1 protein. NbSEC14-silenced plants showed accelerated growth of both the virulent and avirulent R. solanacearum as well as acceleration of disease development. This study may provide useful information for the further analysis of the function of plant Sec14 protein homologs in the regulation of plant immune responses.

Cell death of Nicotiana benthamiana is induced by secreted protein NIS1 of Colletotrichum orbiculare and is suppressed by a homologue of CgDN3

Colletotrichum orbiculare, the causal agent of cucumber anthracnose, infects Nicotiana benthamiana. Functional screening of C. orbiculare cDNAs in a virus vector-based plant expression system identified a novel secreted protein gene, NIS1, whose product induces cell death in N. benthamiana. Putative homologues of NIS1 are present in selected members of fungi belonging to class Sordariomycetes, Dothideomycetes, or Orbiliomycetes. Green fluorescent protein-based expression studies suggested that NIS1 is preferentially expressed in biotrophic invasive hyphae. NIS1 lacking signal peptide did not induce NIS1-triggered cell death (NCD), suggesting apoplastic recognition of NIS1. NCD was prevented by virus-induced gene silencing of SGT1 and HSP90, indicating the dependency of NCD on SGT1 and HSP90. Deletion of NIS1 had little effect on the virulence of C. orbiculare against N. benthamiana, suggesting possible suppression of NCD by C. orbiculare at the postinvasive stage. The CgDN3 gene of C. gloeosporioides was previously identified as a secreted protein gene involved in suppression of hypersensitive-like response in Stylosanthes guianensis. Notably, we found that NCD was suppressed by the expression of a CgDN3 homologue of C. orbiculare. Our findings indicate that C. orbiculare expresses NIS1 at the postinvasive stage and suggest that NCD could be repressed via other effectors, including the CgDN3 homologue.

Repair of Cartilage injuries using in vitro engineered 3D cartilage tissue- Preliminary Results of Our Animal Studies

INTRODUCTION

The cartilage injuries demand novel therapeutic approaches as the success rates of the current conventional strategies for the repair of injured articular cartilages are not that encouraging. Earlier we have reported that the Thermoreversible Gelation Polymer (TGP) is an ideal scaffold for human chondrocyte expansion in vitro. In this study, we report the preliminary results of the in vitro expansion, characterization and experimental in vivo transplantation of chondrocytes in a rabbit model of cartilage injury.

MATERIALS & METHODS

Nine rabbits were included in this study scheduled for two years, after approval by the ethics committee. In the first animal, Chondrocytes were isolated from the weight bearing area of patellar groove in the left hindlimb and cultured in TGP Scaffold and maintained at 37°C in 5% carbon dioxide incubator for 64 days without growth factors. Then the TGP-Chondrocyte construct was transplanted into an experimental defect created in the knee of the right forelimb of the same rabbit. After a period of 10 weeks, a biopsy was taken from the transplanted region and subjected to morphological analysis, characterization by histopathology (H&E stain) and Immunohistochemistry (S-100 staining).

RESULTS

The chondrocytes in the 3D TGP culture had round to oval shaped morphology without any de-differentiation which is otherwise observed in Conventional 2D cultures. A macroscopic structure which resembled cartilage was appreciated in the TGP construct in vitro after 64 days which was then transplanted to the rabbit. The H&E and Immunohistochemistry studies confirmed the presence of chondrocytes in the biopsy tissue.

CONCLUSION

Based on the results, we conclude that the TGP significantly supports the in vitro expansion of chondrocytes for a longer period and the 3D culture using TGP preserves the phenotype of the articular chondrocytes. The tissue thus grown when implanted with the TGP has engrafted well without any adverse reactions and upon confirmation of safety following completion of the entire study with adequate follow-up, human applications could be considered.

Regulatory mechanisms of nitric oxide and reactive oxygen species generation and their role in plant immunity

Rapid production of nitric oxide (NO) and reactive oxygen species (ROS) has been implicated in diverse physiological processes, such as programmed cell death, development, cell elongation and hormonal signaling, in plants. Much attention has been paid to the regulation of plant innate immunity by these signal molecules. Recent studies provide evidence that an NADPH oxidase, respiratory burst oxidase homolog, is responsible for pathogen-responsive ROS burst. However, we still do not know about NO-producing enzymes, except for nitrate reductase, although many studies suggest the existence of NO synthase-like activity responsible for NO burst in plants. Here, we introduce regulatory mechanisms of NO and ROS bursts by mitogen-activated protein kinase cascades, calcium-dependent protein kinase or riboflavin and its derivatives, flavin mononucleotide and flavin adenine dinucleotide, and we discuss the roles of the bursts in defense responses against plant pathogens.

Phosphorylation of the Nicotiana benthamiana WRKY8 transcription factor by MAPK functions in the defense response

Mitogen-activated protein kinase (MAPK) cascades have pivotal roles in plant innate immunity. However, downstream signaling of plant defense-related MAPKs is not well understood. Here, we provide evidence that the Nicotiana benthamiana WRKY8 transcription factor is a physiological substrate of SIPK, NTF4, and WIPK. Clustered Pro-directed Ser residues (SP cluster), which are conserved in group I WRKY proteins, in the N-terminal region of WRKY8 were phosphorylated by these MAPKs in vitro. Antiphosphopeptide antibodies indicated that Ser residues in the SP cluster of WRKY8 are phosphorylated by SIPK, NTF4, and WIPK in vivo. The interaction of WRKY8 with MAPKs depended on its D domain, which is a MAPK-interacting motif, and this interaction was required for effective phosphorylation of WRKY8 in plants. Phosphorylation of WRKY8 increased its DNA binding activity to the cognate W-box sequence. The phospho-mimicking mutant of WRKY8 showed higher transactivation activity, and its ectopic expression induced defense-related genes, such as 3-hydroxy-3-methylglutaryl CoA reductase 2 and NADP-malic enzyme. By contrast, silencing of WRKY8 decreased the expression of defense-related genes and increased disease susceptibility to the pathogens Phytophthora infestans and Colletotrichum orbiculare. Thus, MAPK-mediated phosphorylation of WRKY8 has an important role in the defense response through activation of downstream genes.

Regulatory mechanisms of nitric oxide and reactive oxygen species generation and their role in plant immunity

Rapid production of nitric oxide (NO) and reactive oxygen species (ROS) has been implicated in diverse physiological processes, such as programmed cell death, development, cell elongation and hormonal signaling, in plants. Much attention has been paid to the regulation of plant innate immunity by these signal molecules. Recent studies provide evidence that an NADPH oxidase, respiratory burst oxidase homolog, is responsible for pathogen-responsive ROS burst. However, we still do not know about NO-producing enzymes, except for nitrate reductase, although many studies suggest the existence of NO synthase-like activity responsible for NO burst in plants. Here, we introduce regulatory mechanisms of NO and ROS bursts by mitogen-activated protein kinase cascades, calcium-dependent protein kinase or riboflavin and its derivatives, flavin mononucleotide and flavin adenine dinucleotide, and we discuss the roles of the bursts in defense responses against plant pathogens.

Characterization of aortic aneurysms in cardiovascular disease patients harboring Porphyromonas gingivalis

OBJECTIVE

Porphyromonas gingivalis was recently shown to cause intimal hyperplasia in a mouse model by a novel cholesterol-independent mechanism, suggesting to be a pathogen-specific feature of cardiovascular diseases. The aim of this study was to characterize the clinical and histopathological features of aortic aneurysms in cardiovascular disease patients harboring oral P. gingivalis.

SUBJECT AND METHODS

Aortic aneurysm specimens were collected from 76 Japanese patients who underwent surgery, of whom dental plaque specimens were also collected from 31 patients. Bacterial DNA was extracted from each specimen to detect P. gingivalis by polymerase chain reaction. Histopathological analyses of the aortic aneurysm specimens, including immunohistochemical staining for embryonic myosin heavy chain isoform (SMemb) and S100 calcium-binding protein A9 (S100A9), were also performed.

RESULTS

The number of aneurysms occurring in the distal aorta was significantly higher in subjects positive for P. gingivalis in dental plaque compared with those who were negative. The expressions of S100A9 and SMemb were also significantly greater in the subjects positive for P. gingivalis in dental plaque. On the other hand, there were no significant differences in adipocellular accumulation between the groups.

CONCLUSIONS

These results suggest that aortic aneurysms in patients harboring oral P. gingivalis have greater expression of S100A9 and proliferative smooth muscle cells, which was different from the present patients without oral P. gingivalis.

Role of nitric oxide and reactive oxygen [corrected] species in disease resistance to necrotrophic pathogens

Nitric oxide (NO) and reactive oxygen species (ROS) are important signaling molecules in plant immunity. However, roles of NO and ROS in disease resistance to necrotrophic pathogens are not fully understood. We have recently demonstrated that NO plays a pivotal role in basal defense against Botrytis cinerea and the expression of the salicylic acid (SA) -responsive gene PR-1in Nicotiana benthamiana. By contrast, ROS function negatively in resistance or positively in expansion of disease lesions during B. cinerea-N. benthamiana interaction. Here, analysis in NahG-transgenic N. benthamiana showed that SA signaling is not involved in resistance to B. cinerea in N. benthamiana. We discuss how NO and ROS participate in disease resistance to necrotrophic pathogens on the basis of recent reports.

A key enzyme for flavin synthesis is required for nitric oxide and reactive oxygen species production in disease resistance

Nitric oxide (NO) and reactive oxygen species (ROS) play key roles in plant immunity. However, the regulatory mechanisms of the production of these radicals are not fully understood. Hypersensitive response (HR) cell death requires the simultaneous and balanced production of NO and ROS. In this study we indentified NbRibAencoding a bifunctional enzyme, guanosine triphosphate cyclohydrolase II/3,4-dihydroxy-2-butanone-4-phosphate synthase, which participates in the biosynthesis of flavin, by screening genes related to mitogen-activated protein kinase-mediated cell death, using virus-induced gene silencing. Levels of endogenous riboflavin and its derivatives, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which are important prosthetic groups for several enzymes participating in redox reactions, decreased in NbRibA-silenced Nicotiana benthamiana. Silencing NbRibA compromised not only HR cell death, but also the NO and ROS production induced by INF1 elicitin and a constitutively active form of NbMEK2 (NbMEK2DD), and also induced high susceptibility to oomycete Phytophthora infestans and ascomycete Colletotrichum orbiculare. Compromised radical production and HR cell death induced by INF1 in NbRibA-silenced leaves were rescued by adding riboflavin, FMN or FAD. These results indicate that flavin biosynthesis participates in regulating NO and ROS production, and HR cell death.

Activities and distribution of methanogenic and methane-oxidizing microbes in marine sediments from the Cascadia Margin

We investigated methane production and oxidation and the depth distribution and phylogenetic affiliation of a functional gene for methanogenesis, methyl coenzyme M reductase subunit A (mcrA), at two sites of the Integrated Ocean Drilling Program Expedition 311. These sites, U1327 and U1329, are respectively inside and outside the area of gas hydrate distribution on the Cascadia Margin. Radiotracer experiments using (14)C-labelled substrates indicated high potential methane production rates in hydrate-bearing sediments [128-223 m below seafloor (mbsf)] at U1327 and in sediments between 70 and 140 mbsf at U1329. Tracer-free experiments indicated high cumulative methane production in sediments within and below the gas hydrate layer at U1327 and in sediments below 70 mbsf at U1329. Stable tracer experiments using (13)C-labelled methane showed high potential methane oxidation rates in near-surface sediments and in sediments deeper than 100 mbsf at both sites. Results of polymerase chain reaction amplification of mcrA in DNA were mostly consistent with methane production: relatively strong mcrA amplification was detected in the gas hydrate-bearing sediments at U1327, whereas at U1329, it was mainly detected in sediments from around the bottom-simulating reflector (126 mbsf). Phylogenetic analysis of mcrA separated it into four phylotype clusters: two clusters of methanogens, Methanosarcinales and Methanobacteriales, and two clusters of anaerobic methanotrophic archaea, ANME-I and ANME-II groups, supporting the activity measurement results. These results reveal that in situ methanogenesis in deep sediments probably contributes to gas hydrate formation and are inconsistent with the geochemical model that microbial methane currently being generated in shallow sediments migrates downward and contributes to the hydrate formation. At Site U1327, gas hydrates occurred in turbidite sediments, which were absent at Site U1329, suggesting that a geological setting suitable for a gas hydrate reservoir is more important for the accumulation of gas hydrate than microbiological properties.

Regulation of Arabidopsis defense responses against Spodoptera littoralis by CPK-mediated calcium signaling

BACKGROUND

Plant Ca2+ signals are involved in a wide array of intracellular signaling pathways after pest invasion. Ca2+-binding sensory proteins such as Ca2+-dependent protein kinases (CPKs) have been predicted to mediate the signaling following Ca2+ influx after insect herbivory. However, until now this prediction was not testable.

RESULTS

To investigate the roles CPKs play in a herbivore response-signaling pathway, we screened the characteristics of Arabidopsis CPK mutants damaged by a feeding generalist herbivore, Spodoptera littoralis. Following insect attack, the cpk3 and cpk13 mutants showed lower transcript levels of plant defensin gene PDF1.2 compared to wild-type plants. The CPK cascade was not directly linked to the herbivory-induced signaling pathways that were mediated by defense-related phytohormones such as jasmonic acid and ethylene. CPK3 was also suggested to be involved in a negative feedback regulation of the cytosolic Ca2+ levels after herbivory and wounding damage. In vitro kinase assays of CPK3 protein with a suite of substrates demonstrated that the protein phosphorylates transcription factors (including ERF1, HsfB2a and CZF1/ZFAR1) in the presence of Ca2+. CPK13 strongly phosphorylated only HsfB2a, irrespective of the presence of Ca2+. Furthermore, in vivo agroinfiltration assays showed that CPK3-or CPK13-derived phosphorylation of a heat shock factor (HsfB2a) promotes PDF1.2 transcriptional activation in the defense response.

CONCLUSIONS

These results reveal the involvement of two Arabidopsis CPKs (CPK3 and CPK13) in the herbivory-induced signaling network via HsfB2a-mediated regulation of the defense-related transcriptional machinery. This cascade is not involved in the phytohormone-related signaling pathways, but rather directly impacts transcription factors for defense responses.

S-glycoprotein-like protein regulates defense responses in Nicotiana plants against Ralstonia solanacearum

RsRGA4 (for Ralstonia solanacearum-responsive gene A4) encodes a polypeptide similar to S-locus glycoprotein (SGP) from Brassica rapa and SGP-like proteins from Ipomoea trifida and Medicago truncatula. Therefore, we designated RsRGA4 as NtSGLP (for Nicotiana tabacum SGP-like protein) and NbSGLP (its Nicotiana benthamiana ortholog). NbSGLP is expressed in root, leaf, petal, gynoecium, and stamen. Expression of NbSGLP was strongly induced by inoculation with an avirulent strain of R. solanacearum (Rs8107) and slightly enhanced by inoculation with virulent R. solanacearum (RsOE1-1). Expression of NbSGLP was induced by inoculation with an hrpY-deficient mutant of RsOE1-1 and Rs8107. Expression was also induced by aminocyclopropane carboxylic acid and salicylic acid. Virus-induced gene silencing of NbSGLP enhanced the growth of Rs8107. Growth of RsOE1-1 and appearance of wilt symptoms were also accelerated in silenced plants. Expression of PR-1a and EREBP was reduced, and markers for basal defense, such as callose deposition and reduced vascular flow, were compromised in NbSGLP-silenced plants. Moreover, growth of Pseudomonas cichorii, Pseudomonas syringae pv tabaci, and P. syringae pv mellea was also enhanced in the silenced plants. On the other hand, silencing of NbSGLP did not interfere with the appearance of the hypersensitive response. NbSGLP was secreted in a signal peptide-dependent manner. Agrobacterium tumefaciens-mediated expression of NbSGLP induced PR-1a and EREBP expression, callose deposition, and reduced vascular flow. NbSGLP-induced callose deposition and reduced vascular flow were not observed in salicylic acid-deficient N. benthamiana NahG plants. Taken together, SGLP might have a role in the induction of basal defense in Nicotiana plants.

278 EFFECT OF FOLLICULAR WAVE SYNCHRONIZATION AND SUPERSTIMULATION ON THE NORMALITY OF BOVINE EMBRYOS PRODUCED IN VITRO

We previously reported that follicular wave synchronization by dominant follicle removal on Day 5 and the start of a superstimulatory treatment on Day 7 after ovum pick-up (OPU) was effective to increase oocyte quality (Imai et al. 2008 Reprod. Fertil. Dev. 20, 182). The present study was designed to examine the effect of superstimulatory treatment-induced follicular wave synchronization on quality of embryos obtained by OPU and in vitro production. Japanese Black cows were reared under the same feeding and environmental conditions and 2 OPU sessions were conducted in each cow. The first OPU session was performed in 7 cows at arbitrary days of estrous cycle using a 7.5-MHz linear transducer with needle connected to an ultrasound scanner. Then, follicles larger than 8 mm in diameter were aspirated and CIDR was inserted on Day 5 (the day of first OPU session = Day 0). The cows then received 30 mg of FSH twice a day from Days 7 to 10 in decreasing doses (4, 4, 3, 3, 2, 2, 1, 1 mg per shot) by i.m. injections. Cloprostenol (PGF; 0.75 mg) was administered in the morning of Day 9. The second OPU session was performed 48 h after PGF administration (Day 11) and only follicles larger than 5 mm in diameter were aspirated. The CIDR was removed from the cows just before OPU. Grade 1 and 2 cumulus oocyte complexes were in vitro matured, fertilized (IVF), and cultured as described by Imai et al. (2006 J. Reprod. Dev. 52, Suppl. S19-29). Some zygotes were fixed and stained to check their sperm penetration. Embryo development was monitored by time-lapse cinematography for 168 h after IVF. Cleavage pattern of embryos was classified morphologically into normal and abnormal (including those with multiple fragments, protrusions, 3 to 4 blastomeres, and uneven cell division) groups at their first cleavage. Normal penetration rate of second OPU session was significantly (P < 0.05) higher than that of the first OPU session. There were no differences in the mean percentage of total blastocyst and grade 1 blastocyst rates between the first (45.2 and 46.9%, respectively) and second (47.5 and 41.8%, respectively) OPU sessions. However, the rates of blastocysts developing from embryos that were beyond the 4-cell stage at 48 h after IVF was significantly (P < 0.05) higher after the second OPU session (81.2%) than after the first OPU session (67.4%). Furthermore, a significant difference (P < 0.05) was found in the rates of normal cleavage at the first cell division in embryos that developed to the blastocyst stage between the first and second OPU sessions (53.3% and 73.9%, respectively). These results indicate that superstimulatory treatment-induced follicular wave synchronization improved the normality of fertilization and development of cattle oocytes obtained by OPU. This work was supported by the Research and Development Program for New Bio-industry Initiatives.

Molecular analysis of aortic intimal hyperplasia caused by Porphyromonas gingivalis infection in mice with endothelial damage

BACKGROUND AND OBJECTIVE

Porphyromonas gingivalis infection is thought to be a significant etiological factor in the development of cardiovascular diseases. However, scant definitive evidence has been presented concerning the pathological molecular mechanisms of these disorders. In the present study, we performed a molecular analysis of the developmental mechanisms of aortic intimal hyperplasia induced by P. gingivalis.

MATERIAL AND METHODS

The effects of P. gingivalis-induced bacteremia on intimal hyperplasia were evaluated using a mouse model of aortic hyperplasia created by photochemical-induced endothelial cell injury. Alterations of gene expression profiles in injured blood vessels of the mice were extensively analyzed using DNA microarray assays to identify the key molecules involved in P. gingivalis-induced hyperplasia. In addition, human aneurismal specimens from patients with or without P. gingivalis infection were analyzed histochemically.

RESULTS

Intravenous administration of P. gingivalis dramatically induced intimal hyperplasia in the mouse model. Concomitantly, S100 calcium-binding protein A9 (S100A9) and embryonic isoform of myosin heavy chain (SMemb), a proliferative phenotypic marker of smooth muscle cells, were significantly overexpressed on the surfaces of smooth muscle cells present in the injured blood vessels. Similarly, increased expressions of S100A9 and SMemb proteins were observed in aneurismal specimens obtained from P. gingivalis-infected patients.

CONCLUSION

We found that bacteremia induced by P. gingivalis leads to intimal hyperplasia associated with overexpressions of S100A9 and SMemb. Our results strongly suggest that oral-hematogenous spreading of P. gingivalis is a causative event in the development of aortic hyperplasia in periodontitis patients.

Molecular mechanisms of generation for nitric oxide and reactive oxygen species, and role of the radical burst in plant immunity

Rapid production of nitric oxide (NO) and reactive oxygen species (ROS) has been implicated in the regulation of innate immunity in plants. A potato calcium-dependent protein kinase (StCDPK5) activates an NADPH oxidase StRBOHA to D by direct phosphorylation of N-terminal regions, and heterologous expression of StCDPK5 and StRBOHs in Nicotiana benthamiana results in oxidative burst. The transgenic potato plants that carry a constitutively active StCDPK5 driven by a pathogen-inducible promoter of the potato showed high resistance to late blight pathogen Phytophthora infestans accompanied by HR-like cell death and H(2)O(2) accumulation in the attacked cells. In contrast, these plants showed high susceptibility to early blight necrotrophic pathogen Alternaria solani, suggesting that oxidative burst confers high resistance to biotrophic pathogen, but high susceptibility to necrotrophic pathogen. NO and ROS synergistically function in defense responses. Two MAPK cascades, MEK2-SIPK and cytokinesis-related MEK1-NTF6, are involved in the induction of NbRBOHB gene in N. benthamiana. On the other hand, NO burst is regulated by the MEK2-SIPK cascade. Conditional activation of SIPK in potato plants induces oxidative and NO bursts, and confers resistance to both biotrophic and necrotrophic pathogens, indicating the plants may have obtained during evolution the signaling pathway which regulates both NO and ROS production to adapt to wide-spectrum pathogens.

Vestigial and scalloped in the ladybird beetle: a conserved function in wing development and a novel function in pupal ecdysis

In Drosophila melanogaster, Vestigial (Vg) and Scalloped (Sd) form a transcription factor complex and play a crucial role in wing development. To extend our knowledge of insect wing formation, we isolated vg and sd homologues from two ladybird beetle species, Henosepilachna vigintioctopunctata and Harmonia axyridis. Although the ladybird beetle vg homologues had only low homology with D. melanogaster vg, ectopic expression of H. vigintioctopunctata vg induced wing-like tissues in antennae and legs of D. melanogaster. Subsequent larval RNA interference (RNAi) analysis in H. vigintioctopunctata demonstrated conserved functions of vg and sd in wing development, and an unexpected novel function of sd in pupal ecdysis. Furthermore, our results can be applied to the production of a flightless ladybird beetle for biological control purposes using larval RNAi.

The Colletotrichum orbiculare SSD1 mutant enhances Nicotiana benthamiana basal resistance by activating a mitogen-activated protein kinase pathway

Plant basal resistance is activated by virulent pathogens in susceptible host plants. A Colletotrichum orbiculare fungal mutant defective in the SSD1 gene, which regulates cell wall composition, is restricted by host basal resistance responses. Here, we identified the Nicotiana benthamiana signaling pathway involved in basal resistance by silencing the defense-related genes required for restricting the growth of the C. orbiculare mutant. Only silencing of MAP Kinase Kinase2 or of both Salicylic Acid Induced Protein Kinase (SIPK) and Wound Induced Protein Kinase (WIPK), two mitogen-activated protein (MAP) kinases, allowed the mutant to infect and produce necrotic lesions similar to those of the wild type on inoculated leaves. The fungal mutant penetrated host cells to produce infection hyphae at a higher frequency in SIPK WIPK-silenced plants than in nonsilenced plants, without inducing host cellular defense responses. Immunocomplex kinase assays revealed that SIPK and WIPK were more active in leaves inoculated with mutant fungus than with the wild type, suggesting that induced resistance correlates with MAP kinase activity. Infiltration of heat-inactivated mutant conidia induced both SIPK and WIPK more strongly than did those of the wild type, while conidial exudates of the wild type did not suppress MAP kinase induction by mutant conidia. Therefore, activation of a specific MAP kinase pathway by fungal cell surface components determines the effective level of basal plant resistance.