Novel nuclear protein, NsiA, and its interacting transcription factor Ste12 and MAP kinase Mak2 mediate balanced symbiotic infection of endophytic fungus Epichloë festucae in perennial ryegrass.
S. KAMIYA (1), Y. Ozaki (1), A. Okamura (1), S. Kameoka (1), Y. Kayano (1), S. Sanjay (2), B. Scott (3), J. Maruyama (4), A. Tanaka (1), D. Takemoto (1) (1) Nagoya University, Japan; (2) Massey University, New Zealand; (3) Nagoya University, New Zealand; (4) The University of Tokyo, Japan

The endophytic fungus Epichloë festucae systemically colonize the intercellular spaces of cool-season grasses to establish a mutualistic symbiotic association. The growth of endophyte within host appears to be tightly regulated and synchronized with the growth of host plant, in contrast with destructive overgrowth of most plant pathogens in their host plants. A screen to identify symbiotic genes isolated a mutant FR405 that altered the interaction from mutualistic to antagonistic. Perennial ryegrass infected with FR405 mutant become severely stunted. FR405 has a plasmid insertion in the coding region of uncharacterized Alanine/Glycine/Serine/Proline-rich protein. GFP fusion of this protein was localized to nuclei, thus designated NsiA for nuclear protein for symbiotic infection. By yeast two-hybrid assay, it was shown that NsiA interact with Ste12, a C2H2-Zn2 finger transcription factor, and a MAP kinase Mak2/Fus3. In contrast with severe growth inhibition of host plants infected with nsiA mutant, infection rate of ste12 mutant was significantly decreased, and infection of mak2 mutant have never been detected. RNAseq analysis revealed that the expression of several genes required for symbiotic infection, ProA, Ham8 and Pro41, was down-regulated in the nsiA mutant, but expression of these genes was not significantly altered in mak2 mutant. These results indicated that NsiA, and its interactors, Ste12 and Mak2 have distinct roles in control of symbiotic growth of E. festucae.

Abstract Number: P2-52
Session Type: Poster