Figure 5.

Inducible Overexpression of SEP1 in M. oryzae Leads to Aberrant Nuclear Division.

SEP1 was placed under control of the isocitrate lyase gene promoter sequence to enable induction of gene expression by acetate. Two transformants were isolated, one containing multiple insertions of the ICL1(p):SEP1 construct, SEP1-1, and one containing a single insertion of the transgene, SEP1-9. Ac, sodium acetate; bars =10 μm; error bars are 1 se.

(A) Vegetative growth of SEP1-1 and SEP1-9 transformants. Plugs of mycelium (5-mm diameter) from the SEP1-1 and SEP1-9 strains and the isogenic H1:RFP strain were used to inoculate minimal medium (MM) with or without 50 mM sodium acetate. Hyphal growth was assessed 4 d later.

(B) Quantitative analysis of nuclear number in H1:RFP, SEP1-1, and SEP1-9. Conidial suspensions were prepared and incubated to allow appressorium development in the presence or absence of acetate. Nuclear number was recorded 10 h later.

(C) Representative images to show nuclear distribution during appressorium morphogenesis.

(D) Quantitative analysis of septum formation during appressorium morphogenesis. Conidial suspensions were stained with calcofluor white after 10 h and the number of septa recorded.

(E) Bar charts to show the frequency of appressorium development in the presence or absence of acetate. Appressorium development was recorded 24 h after inoculation.

(F) Representative images of appressorium formation.