Investigation of the role of a candidate effector of wheat stripe rust pathogen in plant immunity

Dagvadorj, Bayantes
The advanced plant molecular biology and plant biotechnology tools were employed in this thesis, in order to understand the role of a candidate effector, PstSCR1, of Puccinia striiformis f. sp. tritici (Pst) causing yellow rust disease in wheat. The homologues proteins of PstSCR1 were found to be only conserved in Pst, and in its closest relative, Puccinia graminis f. sp. tritici (Pgt). When PstSCR1 was expressed in Nicotiana benthamiana with its signal peptide (SP), it provoked the plant defense, whereas no such effect observed when it is expressed without SP, since SP facilitates crossing of proteins through cellular membranes, it is predicted that the effector is only functional (in triggering plant immune response) if secreted into plant apoplast. The subcellular localization of PstSCR1 was also investigated by microscopic analysis; the effector was indeed secreted to apoplast as the same as apoplastic marker C14 protein. It was also observed that the expression of the effector lowered the pathogenicity of Phythophtora infestans and Peronospora tabacina on N. benthamiana leaves, respectively. Moreover, when PstSCR1 was overexpressed, it triggered cell death. Brassinosteroid insensitive 1-Associated Kinase 1 (BAK1/SERK3) silenced N. benthamiana, cell death was remarkably abated, indicating BAK1 dependent function. Although SCR1-purified treatment on N. benthamiana showed a lack of cell death, it resulted in induction of defense genes NbCYP71D20 and NbACRE31, of which are induced in BAK1 dependent immune response. Based on our results, Pst-secreted protein, SCR1 can activate PAMP-triggered immunity on non-adapted hosts and contribute to non-host resistance.  
Citation Formats
B. Dagvadorj, “Investigation of the role of a candidate effector of wheat stripe rust pathogen in plant immunity,” Ph.D. - Doctoral Program, Middle East Technical University, 2016.