Involvement of nitric oxide in acquired thermotolerance of rice seedlings

The role of nitric oxide (NO) in thermotolerance acquired by heat acclimation (38A degrees C) was investigated. Results showed that 38A degrees C acclimation, on the one hand, obviously reduced hydrogen peroxide (H2O2) and MDA contents and ion leakage degree in rice leaves; however, on the other hand, it increased the survival of rice (Oryza sativa L.) seedlings under 50A degrees C heat stress. Application of nitric oxide donor, sodium nitroprusside (SNP), prior to 38A degrees C acclimation dramatically increased the acquired thermotolerance. To elucidate the role of endogenous NO in acquired thermotolerance, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO, a specific NO scavenger) was used (scavengers are used to control the level of both exogenous and endogenous NO). Results showed that PTIO pretreatment resulted in the elimination of acquired thermotolerance induced by 38A degrees C acclimation in rice seedlings. Nitric oxide (NO) release measurement indicated that there was indeed an abrupt elevation in the NO content in 40 min after 38A degrees C acclimation, proving the involvement of NO in acquired thermotolerance inducement in rice seedling.