H₂O₂ Acts Upstream Of NO In Heat Shock Signaling Pathway In Arabidopsis Seedling

Hydrogen peroxide (H2O2) and nitric oxide (NO) have already been identified as signal molecules to participate in heat shock (HS) response in plants. To study how they induce thermotolerance, we investigated the effects heat of on Atrbohb, Atrbohd, Atrbohb/d and noa1 (rif1) mutants seedlings. Firstly, we found that 45℃HS led the accumulation H2O2 in the roots. Under HS, the NO levels and survival ratios of Atrbohb, Atrbohd and Atrbohb/d were all lower than that of WT. Pretreatment of NO donors, SNP and SNAP, both improved the survival ratios of Atrbohb, Atrbohd and Atrbohb/d, whereas pretreatment of H2O2 only improved the survival ratio of WT seedlings but had not effects on noa1(rif1) ones after HS. Real-time PCR analyses demonstrated the transcription of HSP18.2, HSP2 and HSP25.3 were impaired in Atrbohb/d after HS. Western blot analysis was performed to examine HSP21 expression. The result showed that its accumulations were lower in Atrbohb, Atrbohd and Atrbohb/d seedlings than in WT ones, however, pretreatment of SNP and SNAP partially restored the accumulation in Atrbohb/d seedlings. Therefore, we preliminarily concluded that H2O2 might act upstream of NO in thermotolerance in Arabidopsis seedlings.