The Role Of Arabidopsis Thaliana RPW8.1 In The Immune Response Induced By Pathogen-associated Molecular Patterns And The Role Of MiR444b In Rice Blast Resistance

RPW8 is a broad-spectrμM resistance gene to powdery mildew,which was cloned from the wild type Arabidopsis thaliana Ms-0. RPW8 includes two closely linked genes:RPW8.1 and RPW8.2.Both transgenic lines of RPW8.1 and RPW8.2 show broad-spectrum resistance to powdery mildew.In these transgenic lines, RPW8.2 is located on external plasma membrane of haustoria during powdery mildew invading host plant, namely RPW8.2 Wraps haustorias. It is likely that RPW8.2 suppresses the m u Ltiplication of powdery mildew by preventing the exchange of material between haustoria and plant cells. RPW8.1 is located around chloroplast mesophyll cells.In addition, the transgenic lines of RPW8.1 also enhance resistance to downy mildew and oomycetes.however, it is unclear that how RPW8.1 enhances plant disease resistance.At first, through inoculated the wild type arabidopsis thaliana Col-gl and transgenosis lines R1Y4 (pRPW8.1:RPW8.1-YFP) and R2Y4 (pRPW8.2:RPW8.2-YFP) with different kinds of Pseudomonas syringae bacterial strain (P.seudomonas):vir μ Lent strain DC3000, non-toxic strain DC3000(hrcC-)and avir μ Lent strain DC3000(avr Rpm1), DC3000(avrRpt2). We found that RPW8.1 enhances plant resistance to DC3000 and DC3000(hrcC-), while RPW8.2 has no effect on plant resistance through the bacterial growth results. Furthermore, there is no significant difference on the multiplication of DC3000(avrRpml) and DC3000(avrRpt2) between R1Y4, R2Y4 and wild type plants,which indicates that neither RPW8.1 nor RPW8.2 regulate plant ETI.Secondly,We found that PAMPs induced ETI-like responses, such as accumulation of H2O2, HR-like cell death and pathogenesis-related gene transcription, by applying exogenous PAMP molecules (flg22 and chitin), R1Y4 displayed a series of enhanced PAMPs-induced responses, such as MAPK cascade activity,reactive oxygen species burst, callose deposition and transcription ofdefense-related genes.By means of designing and constructing adenylate cyclase reporter system and dual-luciferase reporter system, we found that RPW8.1 could enhance plant’s resistance via reducing virulent effectors secretion and impairing the virulence of effectors.At last, we hybrid R1Y4 with the mutants of PTI Signaling Pathway (fls2,cerkl and bik1) and double mutants fls2/R1Y4,cerkl/R1Y4 and bikl/R1Y4 were selected to test the resistance against pathogens. The results show that RPW8.1-mediated resistance needs the participation of PTI Signaling Pathway.Rice-blast is one of the three major rice diseases that caused by Magnaporthe oryzae, threat globle food safety. The diversity of M. oryzae strains is significantly great in different regions. Therefore, studying the rice resistance to rice blast and searching broad spectrum resistance resources are the scientific needs of controling rice blast nowadays. MiRNAs is a class of highly conservatived small fragments of non-coding RNAs, which are widely exists in animals and plants, miRNAs identify and combine with its corresponding target genes, and suppress the expression quantity of target genes to reg μ Late the growth and development of plant. We constructed miR444b-overexpressed transgenic lines in TP309. The results of qRT-PCR showed that miR444b was over-accumulated in the transgenic lines. We inoculated the detached leaf of transgenic lines with mixed conidial suspension of the rice blast fungus strains, tested the disease symptoms. The results show that the lesions on the transgenic lines are more significant than TP309. Combined with high-throughput sequencing results had analyzed, we predict preliminary that miR444b down-regulate rice resistance to M. oryzae.