Camalexin is not recuired for the function of RPP1 and RPP13 resistance genes in Arabidopsis thaliana inoculated with Peronospora parasitica

Peronospora parasitica bir zorunlu biyotrof patojen olup Arabidopsis thaliana’da mildiyöye sebep olur. A. thaliana ’nın bir ekotipi olan Col-0’dan izole edilen Col- pad3 mutant bitkisinin, daha önce Pseudomonas syringae’nin ırklarıyla inokulasyonundan sonra kamaleksin üretmediği bulunmufltur. Bu mutant bitki P. parasitica ve AgNO3 ile inokulasyondan sonra da tespit edilebilir miktarda kamaleksin üretmemektedir. Hastalıklara dayanıklılık genleri olan RPP1ve RPP13genleri ekotip Nd-1’de üçüncü kromozomun alt kolunda yer almaktadır ve bu genleri tanıyan P. parasitica’nın avirulent ırkları ile inokulasyonu takiben, fidelerde nekrotik lekeler oluflmakta ve patojenin sporulasyonuna rastlanmamaktadır. Bu çalışmada bilinen tek fitoaleksin biyosentetik mutantı olan Col- pad3’ü kullanarak, PAD3 lokusunda meydana gelen mutasyonun, A. thaliana ekotip Nd-1’de bulunan RPP1ve RPP13dayanıklılık genleri üzerindeki etkisini araştırmak hedeflenmiştir. Elde edilen sonuçlara göre, kamaleksinin bu iki dayanıklılık geninin işlevleri için gerekli olmadığı bulunmuştur. Pad3 mutasyonunun Nd-1’de bulunması sonucu bu genotiplerde belli izolatlara karşı duyarlılık gözlenmediğinden, yani hastalık oluflumu meydana gelmediğinden dolayı, kamaleksinin bu iki dayanıklılık geninin işlevleri için gerekli olmadığı bulunmuştur.

Kamaleksin Peronospora parasitica ile inokulasyonundan sonra Arabidopsis thaliana' nın RPP1 ve RPP13 dayanıklılık genlerinin işlevleri için gerekli değildir

Peronospora parasiticais an obligate biotrophic pathogen and causes downy mildew in Arabidopsis thaliana. The Col- pad3 mutant of A. thaliana accession Col-0 was previosly selected in a screen for phytoalexin deficiency following inoculation by the strains of Pseudomonas syringae. The mutant does not accumulate detectable levels of camalexin (the phytoalexin of A. thaliana) following inoculation with P. parasitica or abiotic inducer $AgNO_3$. RPP1and RPP13resistance genes lie at the bottom arm of chromosome three of accession Nd-1. Inoculation of Nd-1 plants with RPP1- and RPP13-avirulent isolates of P. parasiticaresult pitting necrosis on the cotyledons and flecking chlorosis of the seedlings with no pathogen sporulation. In this research, this only known possible phytoalexin biosynthetic mutant was employed to investigate whether the mutation in PAD3locus would have any effect on the recognition of certain isolates of P. parasitica by RPP1 and RPP13 disease resistance genes in A. thalianaaccession Nd-1. According to the results camalexin is not required for the function of these two disease resistance genes.

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Aarts N, Metz M, Holub E, Staskawicz BJ,Daniels MJ and Parker J. Different requirements for EDS1 and NDR1 by disease resistance genes define at least two R gene-mediated signalling pathways in Arabidopsis. Proc of the Nat Ac of Sci USA. 96: 10307-10311, 1998.
Bittner-Eddy P, Can C, Gunn N, Pinel M, Tör M, Crute I, Holub E and Beynon J. Genetic and physical mapping of the RPP13 locus in Arabidopsis responsible for specific recognition of several Peronospora parasitica (downy mildew) isolates. Mol Plant-Microbe Int. 12: 792-802, 1999.
Bittner-Eddy PD, Crute IR, Holub EB and Beynon JL. RPP13 is a simple locus in Arabidopsis thaliana for alleles that specify downy mildew resistance to different avirulence determinants in Peronospora parasitica. The Plant Journal 21: 189-214, 2000.
Botella MA, Parker JE, Frost LN, Bittner-Eddy PD, Beynon JL, Daniels MJ, Holub EB and Jones JDG. Three genes of Arabidopsis RPP1 complex resistance locus recognise distinct Peronospora parasitica avirulence determinants. The Plant Cell. 10: 1847- 1860, 1998.
Browne LM, Conn KL, Ayer WA and Tewari JP. The camalexins: new phytoalexins produced in the leaves of Camelina sativa (Cruciferae). Tetrehedron. 47: 3909- 3914, 1991.
Dixon RA, Lamb CJ, Sewalt VJH and Paiva NL. Metabolic engineering: Prospects for crop improvement through the genetic manipulation of phenylpraponoid biosynthesis and defence responses- a review. Gene. 179: 61-71, 1996.
Glazebrook J. and Ausubel FM. Isolation of phytoalexin-deficient mutants of Arabidopsis thaliana and characterisation of their interactions with bacterial pathogens. P roc of the Nat Ac of Sci USA. 91: 8955- 8959, 1994.
Glazebrook J, Zook M, Mert F, Kagan I, Rogers EE, Crute IR, Holub EB, Hammerschmidt R and Ausubel FM. Phytoalexin-deficient mutants of Arabidopsis reveal that PAD4 encodes a regulatory factor and that four PAD genes contribute to downy mildew resistance. Genetics. 146: 381-392, 1997.
Holub EB, Beynon JL and Crute IR. Phenotypic and genotypic characterisation of interactions between isolates of Peronospora parasitica and accessions of Arabidopsis thaliana. Mol Plant Mic Int. 7: 223-239, 1994.
Holub EH. Organisation of resistance genes in Arabidopsis. In: The Gene-For-Gene Relationship in Plant-Parasite Interactions. Crute IR, Holub EB and BurdonJJ (Eds). CAB International. 5-26, 1997.
Holub EB and Beynon JL. Symbiology of mouse-ear cress (Arabidopsis thaliana) and Oomycetes. Adv in Bot Res. 24: 227-272, 1997.
Kúc J. Phytoalexins, stress metabolism, and disease resistance in plants. Annu Rev of Phytopathol. 33: 275- 297, 1995.
Mansfield JW. Role of phytoalexins in disease resistance. In: Phytoalexins. Mansfield JW and Bailey J (Eds). Blackie, Glasgow. 1982.
Mansfield JW. Antimicrobial compounds and resistance: the role of phytoalexins and antianticipins. In: Mechanisms of Resistance to Plant Diseases. Slusarenko AJ, Fraser RSS and VanLoon LC (Eds). Kluwer, Amsterdam. 1999.
Mert-Türk F, Bennett MH, Glazebrook J, Mansfield J and Holub E. Biotic and abiotic elicitation of camalexin in Arabidopsis thaliana. 7th International Congress of Plant Pathology. Edinburgh, Scotland, UK.1998.
Mert-Türk F. Quantification of enhanced downy mildew susceptibility and camalexin accumulation in the mutants of Arabidopsis thaliana. PhD thesis. University of London, Imperial College of Science, Technology and Medicine, UK. 2001.
Nam HG, Giraudat J, Den Boer B, Moonan F, Loos WDB, Hauge BM and Goodman HM. Restriction fragment polymorphism lincage map of Arabidopsis thaliana. Plant Cell. 1: 699-705, 1989.
Oppenheimer DG, Herman PL, Sivakumarin S, Esch J and Marks MD. A myb gene required for leaf trichome differentiation in Arabidopsis is expressed in stipules. Cell. 67: 483-493, 1991.
Thomma BPHJ, Nelissen I, Eggermont K and Broekaert F. Deficiency in phytoalexin production causes enhanced susceptibility of Arabidopsis thaliana to the fungus Alternaria brassicola. The Plant Journal. 19: 163-171, 1999.
Tör M, Holub EB, Brose E, Musker R, Gunn N, Can C, Crute IR and Beynon JL. Map position of three loci in Arabidopsis thaliana associated with isolate-specific recognition of Peronospora parasitica (downy mildew). Mol Plant Mic Int. 7: 214-222, 1994.
Tsuji J, Jackson EP, Gage DA, Hammerschmidt R and Somerville SC. Phytoalexin accumulation in Arabidopsis thaliana during the hypersensitive reaction to Pseudomonas syringae pv. syringae. Plant Physiol. 98: 1304-1309, 1992.