Identification of a putative protease inhibitor involved in three different Puccinia-triticum aestivum interaction

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Date
2013
Authors
Scholtz, Jakobus Johannes
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University of the Free State
Abstract
English: The Bowman-Birk family of plant protease inhibitors are serine protease inhibitors that can simultaneously inhibit trypsin and/or chymotrypsin. Unique features include an unusually high thermal stability, tolerance towards low pH and resistance towards the action of proteases. Bowman-Birk protease inhibitors have been implicated in various biotic and abiotic stress conditions in plants. LRW222 was recently identified by means of SSH in Puccinia triticina-infected wheat and was found to be homologous to Wali5, a wound- and aluminium stress-induced Bowman-Birk type protease inhibitor. The aim of this study was to determine the expression levels and role of the LRW222 protein in Pucciniainfected wheat. This study identified and validated stable reference genes for qPCR gene expression analysis in rust-infected wheat. qPCR is the preferred method to quantify mRNA levels, but requires validated reference genes for data normalisation. As prescribed by the MIQE guidelines, the GeNorm-Plus algorithm was used to examine the expression stability of six candidate reference genes in resistant Avocet Yr1 wheat infected with P. triticina, P. striiformis and P. graminis f. sp. tritici respectively. These reference genes were used in the gene expression analysis of LRW222. Results indicated induced expression in both resistant and susceptible wheat, indicating its possible involvement in the early general defence response of wheat. Co-immunoprecipitation and mass spectrometry was used in an attempt to identify LRW222-interacting proteins to shed light on its specific role in plant defence. Protein identification was inconclusive, but results indicated that under natural conditions, LRW222 may exist as multimers in wheat.
Afrikaans: Die Bowman-Birk familie van plant protease inhibeerders is serien protease inhibeerders wat gelyktydig tripsien en/of chimotripsien kan inhibeer. Hul unieke kenmerke sluit 'n buitengewoon hoë termiese stabiliteit, toleransie teenoor lae pH en weerstand teenoor die aksie van proteases in. Bowman-Birk protease-inhibeerders is by verskeie biotiese en abiotiese strestoestande in plante betrokke. LRW222 is onlangs deur middel van SSH geïdentifiseer in Puccinia triticina-geïnfekteerde koring en homologie was met 'n wonden aluminium stres-geïnduseerde Bowman-Birk tipe protease inhibitor, naamlik Wali5, gevind. Die doel van hierdie studie was om die uitdrukking en rol van die LRW222 proteïen in Puccinia-geïnfekteerde koring vas te stel. Hierdie studie het stabiele verwysingsgene vir qPCR geenuitdrukking-analise in roesgeïnfekteerde koring geïdentifiseer en bevestig. qPCR is die voorkeur metode om mRNA transkripsie-vlakke te kwantifiseer, maar vereis die gebruik van stabiele verwysingsgene vir data normalisering. Soos voorgeskryf deur die MIQE riglyne, was die GeNorm-Plus algoritme gebruik om die uitdrukkings-stabiliteit van ses moontlike verwysingsgene in Avocet Yr1 koring geïnfekteer met P. triticina, P. striiformis en P. graminis f. sp. Tritici onderskeidelik, te ondersoek. Hierdie verwysingsgene was tydens die geenuitdrukkingsanalise van LRW222 gebruik. Die resultate het geïnduseerde uitdrukking in beide weerstandbiedende en vatbare koringlyne aangedui, wat op die moontlike betrokkenheid van LRW222 in die vroeë algemene verdedigingsrespons van koring dui. Koimmunopresipitering en massa-spektrometrie was gebruik in 'n poging om proteïene wat interaksie met LRW222 toon te identifiseer, om sodoende lig te werp op sy spesifieke rol in plantverdediging. Proteïen identifikasie was onoortuigend, maar die resultate het aangedui dat LRW222 moontlik as multi-grootte multimere onder natuurlike toestande in koring teenwoordig is.
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Reference genes, GeNorm, Triticum aestivum, Puccinia graminis f. sp. tritici, Puccinia triticina, Puccinia striiformis, Wheat -- breeding, Triticum aestivum, Dissertation (M.Sc. (Plant Sciences))--University of the Free State, 2013
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