Figure 8. Overexpression of MIR9863a and MIR9863b attenuates Mla1-triggered disease resistance and cell-death signaling.

(A) Transient gene expression of MIR9863a, MIR9863c and MIR9863b in barley near-isogenic line containing Mla1 or Mla10. Empty vector or plasmids expressing indicated MIRNA precursors were delivered into leaf epidermal cells of indicated barley lines through particle bombardment, and spores of indicated avirulence Bgh isolates were inoculated 36 hrs post bombardment. Haustorial index shown are the percentage of cells that developed fungal haustoria in all transformed cells. (B) Transient gene expression assays in Golden promise (GP), a barley line susceptible to both Bgh K1 and Bgh A6. Indicated construct expressing MIR9863b was delivered alone or with Mla1-mYFP or Mla10-mYFP construct into GP leaf epidermal cells, and spores of Bgh K1 or Bgh A6 were inoculated at 4 hrs post bombardment. Error bars in (A) and (B) represent standard error (SE) from at least three replicates, and letters (a–c) above the bars represent groups with significant differences [p<0.05, Tukey's honest significant difference (HSD) test]. (C) to (D) Analysis of cell-death induction upon co-expressing Mla1 or Mla10 with MIR9863a and MIR9863c. The indicated constructs were expressed in N. benthamiana leaves by Agro-infiltration, and cell death was visualized by trypan blue staining at 48 hours-post-Agro-infiltration (hpai). Red circle indicates visible cell-death phenotype.