| Rice blast caused by Magnaporthe oryza is one of the three major diseases of rice, which is the most destructive for rice. Nowadays, the main strategy to control this disease is selecting and breeding resistant rice cultivars, along with chemical prevention. Due to the reason that the physiological races of these pathogens, which are extremely variable, have a great diversity all around the world, fine resistant rice cultivars will soon lose their resistance. Thus, the further study of the growth and pathogenesis of pathogens and the function of all kinds of materials and structures in the process of infection process will have very important significance. In recent years, the announcement of the whole genome sequence of rice blast fungus and the improvement of the genetic transformation system have provided great convenience for further study of a variety of pathogenic genes and its important physiological functions. Besides, they provide new targets for the new fungicides against the rice blast and reliable theoretical basis for control strategies for rice blast.Myosin is a kind of linear molecule motors, which can use the chemical energy produced by the hydrolysis of ATP to move along the orbit made of actin filament. One traditional myosin named myosin Ⅱ supplies power for muscle contraction in muscle cells. Further study found that myosin Ⅱ widely distributed in the non-muscle cells as cytoskeleton provides the required energy for physiological processes, such as the movement of organelles, flowing action of the cytoplasm, transporting of materials, cytokinesis, mitosis, and polarized cell growth. What’s more, it is involved in the important physiological processes of cell endocytosis, secretion, fertilization, movement, absorption, etc. Myosin Ⅱ plays the role of regulator in the different levels of various biological activities of non-muscle cells, ranging from molecular signals transmission between simple cells to high-level regulation of various tropism migrations, cell morphological changes and so on.In Saccharomyces cerevisiae, myosin V encoded by Myo2p, a kind of molecular motors, shaped like letter "Y", is a elongated asymmetry molecular. It units with two branches at the top of the "Y" and moves along the orbit to transport substances. Myosin V is involved in secretion of vesicles and vacuole, and polarization transportation of late Golgi apparatus components, peroxidase and mitotic spindle, so Myo2p plays an important role in yeast vesicular transport. Myosin II was encoded by FgMY02 in Fusarium graminearum. As results of the deletion of FgMY02 gene, the cytokinesis of the fungus was severely damaged; the ability to produce conidium dramatically decreased and altered conidia shape appeared in the mutants. Besides, the pathogenicity and produced toxin significantly decreased and chitin distribution was affected.In order to define the biological function of Myo2 in M. oryzae, we identify a gene named MoMYO2, who shows homology with S.cerevisiae MY02, according to the homologous comparison of genome sequence between the sequence of yeast Myo2p and M.oryzae. Sequence analysis showed that this gene, whose coding sequence was 4770 bp and encoding was 1590 amino acids, contained 5 introns. There was a specific MYSc structure domain of myosin in 68-782 amino acids sequence, six IQ motifs in 783-924 amino acids sequence and a DIL domain and a low complexity area on the carboxyl terminus. According to the principle of homologous recombination, protoplast transformation method was used to obtain the knockout mutant AMomyo2. Analysis of Biological characters showed that the vegetative growth of knockout mutant AMomyo2 was obviously restrained; The sensitivity to the a variety of cell wall stress and hydrogen peroxide stress decreased, but the sensitivity to osmotic stress enhanced; the ability of △Momyo2 to produce conidium lost and the pathogenicity reduced because extension of infected hypha formated by appressorium in the host cells was restrained. More importantly, we validated the MoMYO2 has interaction with genes MoSEC4 and MoSEC15 related with vesicular transport by yeast hybrid experiments. Thus, we can predict that MoMyo2 participated in the vesicular transport process of rice blast fungus. |
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