Functional interaction between nitric oxide and hydrogen peroxide during formation of wheat seedling induced heat resistance

The involvement of nitric oxide (NO) and hydrogen peroxide (H 2 O 2 ) in the formation of heat resistance induced by 1-min-long treatment with a temperature of 42°C in 3-day-old seedlings of winter soft wheat ( Triticum aestivum L., cv. Elegiya) was studied. The content of NO in the roots was increased within 2 h after seedling hardening heating. The content of H 2 O 2 was increased within 30 min after heating. This effect was neutralized when seedlings were treated with the nitric oxide scavenger PTIO (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) and the inhibitor of NO synthase L-NAME (N G -nitro-L-arginine methyl ester). Seedling treatment with the antioxidants ionol and dimethylthiourea (DMTU) reduced the hardening-induced nitric oxide accumulation in tissues. When seedlings were treated with the NO donor sodium nitroprusside (SNP), the amount of endogenous NO and H 2 O 2 in them increased; exogenous hydrogen peroxide affected similarly. Hardening heating and treatment with SNP and hydrogen peroxide increased seedling resistance to damaging heating, whereas NO antagonists (PTIO and L-NAME) and antioxidants (ionol and DMTU) prevented the development of seedling heat resistance after hardening heating. It is concluded that, during the induction of wheat seedling heat resistance by the hardening heating, functional interaction between NO and H 2 O 2 as signaling messengers occurs.