Disequilibration of Pik-H4 expression did not affect rice
blast resistance
The Pik gene pairs trigger HR together facing Avr and form a
complex (ZdrzaĆek et al., 2020a). Considering the co-regulation of thePik-H4 gene pair via the BDP, we investigated whether the
disequilibration of Pik-H4 expression had any influence on rice
blast resistance. Remarkably, the overexpression of eitherPik1-H4 or Pik2-H4 in LTH
did not confer disease resistance (Figure 5A-C). Conversely, withinPik-H4 NILs, overexpression of eitherPik1-H4 or Pik2-H4sustained rice blast resistance. Interestingly, overexpression of eitherPik-H4 in LTH led to an enhancement in the expression of the
other Pik gene in LTH (Figure 5D). The relative expression levels
analysis showed overexpressing one of the Pik-H4 in Pik-H4NILs up-regulated the counterpart (Figure 5E). This intriguing
regulatory relationship was successfully replicated in tobacco, yielding
analogous outcomes (Figure 5F). These findings collectively suggest
that, facilitated by the PPik-H4 , the expression
levels of Pik-H4 are self- and co-regulated. To eliminate the
innate regulation of Pik-H4 in rice, agroinfiltrations of
different ratios of Pik-H4 with 35S promoter were
performed in tobacco (Figure 5G). At the protein level, combinations of
Pik1-H4 and Pik2-H4 in 1:1, 1:2, or 2:1
ratios failed to induce HR in the absence of AvrPik-E. However, upon the
introduction of AvrPik-E, these combinations exhibited activity in ion
leakage assays, with similar conductivity levels recorded at 3 dpi.
These results suggested that altering the disequilibration ofPik-H4 in protein levels did not compromise rice blast
resistance.