The Function Analysis Of Pmkk1, Cpka And MagA In The Mutualistic Interaction Between The Endophyte (Harpophora Oryzae) And Rice

Mitogen-activated protein kinase (MAPK) cascades and cAMP-protein kinase A (PKA) pathways are essential for vegetative growth, development and reproduction of many pathogens fungi. Core elements involved in those pathways are indispensable for virulence in fungal pathogens of mammals and plants. So far, the mechanism of these two significant classes of signaling pathways had been widly studied in fungal pathogens, but there are barely reserached in endophytic fungi. As beneficial fungi, endophytes have potencial effects on the biocontrol for improving resistances of the host against biotic and abiotic stresses. Therefore, it is really worth investigating the mechanism of MAPK and cAMP signal pathway in the fungal endophyte-plant inteaction.As a dark septate endophyte, Harpophora oryzae was islaoted from wild rice roots, and it shows highly biocontrol potential against rice blast disease caused by Magnaporthe oryzae. According to the protein sequence analysis, Pmkl, Cpka and MagA involved in MAPK and cAMP signal pathways showed significantly identities with the homologs genes in the pathogens fungi, respectively. In this study, we identified Pmkl, Cpka and MagA, and further characterized the function of them by the gene knock-out strategy.Pmkl mutant of H. oryzae reduced vegetative growth and melanin accumulation significantly. Meanwhile, topical inoculation showed that△Pmk1can not grow invasively in the wounded barley leaves and rice roots. Unlike△Pmk1, targeted deletion of Cpka or MagA did not effect appressoria formation. Meanwhile,△Cpka and AMagA still have the ability to infect and colonize the wounded barley leaves and rice leaves. Deletion of Cpka blocked conidiation and reduced vegetative growth, while there are no effect on both conidiation and vegetative growth in△MagA. Besides, the deletion of these genes didn’t affect the cell wall integrity, meaning that they didn’t participate in the construction of cell wall.In summary, our data demonstrated that Pmkl plays an essention role in vegetative growth, melanin accumulation and appressoria formation, highlighting the significance of MAPK function for endophyte-plant inteaction. Moreover, as the cAMP-dependent protein kinase catalytic subunit, Cpka regulated H. oryzae vegetative growth and conidiation. MagA, a G protein a subunit, is not involved in controlling vegetative growth, fungal conidiation, and the symbiotic balance between H. oryzae and Rice.