Functional Analysis Of Transcription Factor PSBZP1in Phytophthora Sojae

Phytophthora sojae is a kind of oomycete so different from fungi on phylogenetic relationships, biological characters and pathogenic mechanism that most fungicides are failed to cure the root rot disease. Besides, because of the genomic instability of P. sojae, the genes are easily to mutant, causing quickly resistance to fungicide. With the completion of genome sequencing of4kinds of Phytophthora, it is possible to research the molecular pathogenic process of P. sojae, helping develop a new method to prevent the root rot disease. In this thesis, bioinformatics analysis as well as PEG-mediated transform system provided an effect method to identify the downstream regulated genes of PsSAK1and their gene functions. It helps to know much about the molecular infection mechanism of P. sojaeTranscription factors (TFs) play a critical role in regulating gene expression and responding to specific signal pathway. To identify the key factor in pathegetic process of P. sojae, we predicted17bZIP TFs from the genome. The result of bioinformatics analysis shows that the sequences of bZIP TFs in P. sojae have low similarity and locates on different scaffolds in genome, except that PsI28339and PsI28400located on the scaffold4. It is predicted that there are5motifs in the bZIP TFs by online tool MEME. According to different transcript patterns, we separated the bZIP TFs into5classes, most of which express much higher in the zoospore, cyte, germination cyte and infection stages. According to the differentially expressed genes, we speculate that the bZIP TFs of P. sojae are related to not only growth and development of zoospores and cytes but also the infection of P. sojae. Bioinformatics analysis supplies the important clues of follow up learning of gene functions.PsSAKl, encoding a MAP kinase, is an important regulator of zoospore development and pathogenicity in P. sojae. To find the TF which is downstream regulated by PsSAKl, we choose3candidates that are down-regulated in the CY and IF1.5in the PsSAK1-silenced lines. PsBZPl is a bZIP TF with a full length of1622bp, containing5 introns, encoding a protein at413animo acids. PsBZP1is up-regulated in zoospore, cyte, germination cyte and infection stages. To elucidate the function, the expressions of3candidates were silenced by transience silencing of P. sojae. Compaired with the wild type, the silenced strains, which relevant expression level is30%and40%, showed quicker encystment and higher germination ratio about27.5%and78%respectively. The zoospores of PsBZP1-silenced mutants swam in circle instead of swimming straight ahead, and the abnormal ratio is39.3%. Moreover, the cytes of them germinated abnormal germ tubes, much shorter and curvier on the top of the tubes, at the ratio of72.3%.PsBZP1-silenced mutants were unable to infect neither the soybean leaves nor the etiolated seedlings. Our results indicate that PsBZP1is an important TF, which possibly is in the downstream of PsSAK1, regulating zoospore development and pathogenicity in P. sojae.