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Defence Genes (defence + gene)

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Life Sciences	100%

Selected Abstracts

The potato StLTPa7 gene displays a complex Ca2+ -associated pattern of expression during the early stage of potato,Ralstonia solanacearum interaction

MOLECULAR PLANT PATHOLOGY, Issue 1 2009
GANG GAO
SUMMARY Although nonspecific lipid transfer proteins (nsLTPs) are widely expressed during plant defence responses to pathogens, their functions and regulation are not fully understood. In this article, we report the isolation of a cDNA for the new nsLTP, StLTPa7, from cultivated potato (Solanum tuberosum) infected with Ralstonia solanacearum. The cDNA was predicted to encode a type 1 nsLTP containing an N-terminal signal sequence and possessing the characteristic features of nsLTPs. A phylogenetic analysis showed that the encoded amino acid sequence of the nsLTP was similar to those of other previously reported plant nsLTPs, which contain a putative calmodulin-binding site consisting of approximately 12 highly conserved amino acid residues. The expression of the StLTPa7 gene was studied during the early stages of potato,R. solanacearum interaction using real-time quantitative polymerase chain reaction (qRT-PCR) and Northern analyses, and a complex calcium (Ca2+)-associated pattern of expression was observed with the following features: (i) transcripts of the StLTPa7 gene were systemically up-regulated by infection with R. solanacearum; (ii) the StLTPa7 gene was stimulated by salicylic acid, methyl jasmonate, abscisic acid and Ca2+; (iii) qRT-PCR showed that, during the early stage of R. solanacearum infection, nsLTP transcripts accumulated over a time course that paralleled that of Ca2+ accumulation, detected using environmental scanning electron microscopy and energy-dispersive X-ray (EDAX) spectrometry; and (iv) the Ca2+ channel blocker, ruthenium red, partially blocked R. solanacearum -induced StLTPa7 expression. This report represents the first use of EDAX analysis to establish a synchrony between Ca2+ accumulation and nsLTP expression in response to potato,R. solanacearum interactions. Collectively, these results suggest that StLTPa7 may be a pathogen- and Ca2+ -responsive plant defence gene. [source]

Analysing scots pine defence-related transcripts and fungal DNA levels in seedlings single- or dual-inoculated with endophytic and pathogenic Rhizoctonia species

FOREST PATHOLOGY, Issue 6 2009
H. Grönberg
Summary Fungal DNA and induction of host defence-related transcripts were monitored by real-time PCR in young Scots pine seedlings inoculated with pathogenic uninucleate (UNR) and endophytic binucleate (BNR) Rhizoctonia species. The UNR (teleomorph Ceratobasidium bicorne) causes root dieback in conifer seedlings following invasion of the vascular cylinder via root apex and destroying apical meristems whilst the BNR, representing anastomosis group AG-I of genus Ceratobasidium, is primarily restricted to the cortex in basal root regions. In the experiment 1 the fungi were simultaneously inoculated on roots, while in experiment 2, BNR was pre-inoculated 168 h before inoculation with UNR. Nucleic acids were extracted from infected roots at intervals up to 192 h post-infection (hpi), and the genomic DNA levels of the host and fungi and the transcript levels of a house-keeping gene (glyceraldehyde-3-phosphate dehydrogenase) and nine putative defence genes were quantified. In simultaneous inoculation UNR was more competitive than BNR whereas pre-inoculation of BNR suppressed but did not completely prevent root colonization by UNR. Stilbene synthase (STS) transcription was significantly up-regulated in single-inoculations with both fungi and in dual inoculation in both experiments. Maximum STS transcript levels were observed in roots single-inoculated with UNR; the peak level at 48 hpi in experiment 2 was significantly higher than in seedlings single-inoculated with BNR or co-inoculated with both fungi, the latter two treatments showing relatively similar STS transcript levels. Similarly, transcript levels of phenylalanine ammonia lyase at 48 hpi in experiment 2 were significantly higher in roots single-inoculated with UNR compared with BNR or in UNR+BNR co-inoculations. The other seven putative defence genes monitored did not show any clear-cut up-regulation following fungal inoculation. We conclude that BNR suppresses UNR in Scots pine roots via direct competition for infection sites, since the studied transcripts showed no evidence of BNR induced resistance against UNR. [source]

UV-B-induced DNA damage and expression of defence genes under UV-B stress: tissue-specific molecular marker analysis in leaves

PLANT CELL & ENVIRONMENT, Issue 9 2001
G. Kalbin
Abstract The aim of this study was to investigate the regulatory effect of ultraviolet-B (UV-B) radiation on a number of key stress response genes found in the epidermis and mesophyll of Pisum sativum L., Argenteum mutant. This mutant was chosen for the ease with which the entire epidermis can be removed from the mesophyll tissue. An additional goal was to explore the potential modifying effect of pre-acclimation of plants to UV-B radiation prior to exposure by UV-B during treatment. Results showed that mRNA accumulation was similar during acute short-term UV-B exposure for chalcone synthase (Chs) and short-chain alcohol dehydrogenase (SadA) in both epidermis and mesophyll. In contrast, the mRNA levels differed considerably between tissues for phenylalanine ammonia lyase, chalcone isomerase and lipid transfer protein. After 24 h incubation in visible light after cessation of UV-B exposure, the regulation of mRNA levels also differed between Chs and SadA, the former showing no expression in the epidermis and the latter none in the mesophyll. Acclimation to low UV-B levels before acute exposures resulted in delayed induction of Chs and SadA. Measurements of UV-B-induced cyclobutane pyrimidine dimers (CPDs) showed a greater formation in epidermis than in mesophyll. In addition, acclimation at low UV-B levels resulted in significantly higher basal levels of CPDs than in non-acclimated plants in both mesophyll and epidermis and also in increased damage in concomitant acute exposures. The lack of correlation between the number of CPDs and levels of transcripts for defence genes, indicates that DNA damage does not control transcription of these genes. [source]

A tomato mutant that shows stunting, wilting, progressive necrosis and constitutive expression of defence genes contains a recombinant Hcr9 gene encoding an autoactive protein

THE PLANT JOURNAL, Issue 3 2006
Claire L. Barker
Summary The tomato Cf-9 gene confers resistance to races of the leaf mould fungus Cladosporium fulvum that carry the Avr9 avirulence gene. Cf-9 resides at a locus containing five paralogous genes and was isolated by transposon tagging using a modified maize Dissociation (Ds) element. The tagging experiment generated an allelic series of Ds -induced mutations of Cf-9, most of which were wild type in appearance. However, one mutant, designated M205, showed stunted growth, wilting, progressive leaf chlorosis and necrosis and constitutive expression of defence genes. The phenotype of M205 was caused by a semidominant, Avr9 -independent mutation that co-segregated with a Ds element insertion at the Cf-9 locus. Molecular genetic analysis indicated that the Cf-9 locus of M205 had undergone recombination, generating a chimeric gene, designated Hcr9-M205, that comprised an in-frame fusion between the 5, coding region of the Cf-9 paralogue, Hcr9-9A, and the 3, coding region of Cf-9. The presence of a possible excision footprint adjacent to the junction between Hcr9-9A and Cf-9, and a Ds insertion at the homologous position in the downstream paralogue Hcr9-9D, is consistent with recombination between Hcr9-9A and Cf-9 promoted by transposition of Ds from Cf-9 into Hcr9-9D. Agrobacterium tumefaciens -mediated transient expression of Hcr9-M205 in Nicotiana tabacum caused chlorosis and the accumulation of defence gene transcripts, indicating that the protein encoded by this novel Hcr9 gene is autoactive. [source]

Enhanced resistance to foliar fungal pathogens in carrot by application of elicitors

ANNALS OF APPLIED BIOLOGY, Issue 1 2009
J. Jayaraj
Abstract Treatment of greenhouse-grown carrot plants with salicylic acid (SA) (100 ,m), chitosan (0.02%) and the nutrient-chelate product Alexin (1%) followed 10 h later by inoculation with the necrotrophic fungal pathogens Alternaria radicina and Botrytis cinerea significantly reduced disease development 10 days after inoculation (d.a.i.) compared with control plants sprayed with water. The most effective treatment was chitosan, followed by Alexin and SA. Additional sprays of elicitors resulted in significantly lower disease development 25 d.a.i. Treated plants had elevated transcript levels of pathogenesis-related protein 1 (PR1), chitinase, lipid transfer protein (LTP), chalcone synthase, nonexpressor of PR1 and pathogenesis-related protein 5 (PR5) genes compared with control plants when assayed 10,70 h after treatment. The activity of peroxidase, polyphenoloxidase, phenylalanine ammonia-lyase, chitinase, ,-1,3-glucanase and lipoxygenase was significantly increased in elicitor-treated plants compared with control plants 12,72 h after treatment. Microscopic examination of treated leaves revealed reduced fungal growth and colonisation, 48 h after treatment, accompanied by fewer lesions at 120 h, compared with the control. Protein extracts from elicitor-treated plants reduced spore germination and germ tube elongation of the pathogens in vitro by 30,45%. Elicitor-treated plants accumulated higher amounts of total phenolics, 6-methoxymellin and H2O2 compared with the control. Both chitosan and Alexin induced responses similar to that of SA, suggesting that these elicitors may activate the salicylate pathway, leading to induction of defence genes, enzymes, phytoalexin and phenolics, which collectively reduced fungal colonisation. [source]