The Fucitions Of CAMP In The Enhancement Of Maizes SHSPs-induced From Heat Stress

In In higher plants,cyclic adenosine monomphsopate（cAMP）which is synthetized by adenylate cyclase,as a key component in many signaling pathways,involves in various physiological reactions,including the response to biotic and abiotic stresses.In Arabidopsis thaliana,the cAMP content is increased significantly in the heat stress,which further induces the expression of heat shock gene（HSPs）,thus improving the thermal stress tolerance.However,the effect of cAMP on maize under heat stress is not clear.Therefore,by using maize plants and leaf protoplasts as experimental material,the role of cAMP in improving maize tolerance to heat stress was studied,the main results were as follows:1 In After 0.5 h,1h and 2 h for drought,heat,combined drought and heat stress treatment,the results showed that the content of cAMP under three stresses were significantly increased after 0.5 h with comparison with control,but the increase continued for 1h and 2 h.Therefore,we selected 1 h as the stress treatment time.After drought,heat,drought and combined both stresses,the content of cAMP in leaves and roots of maize was measured.The results showed that three stresses all significantly increased the content of cAMP in the leaves and roots of maize compared with control,but the combination of drought and heat stress had the most increase,followed by heat stress.2 After pretreatment with 100 μM 8-Br-cAMP and then subjected to heat stress,the effects of exogenous cAMP on the content of H₂O₂,MDA,antioxidant enzyme activity and s HSPs gene expression under high temperature stress were studied.The results showed that,compared with the control,heat stress significantly increased the content of H₂O₂,MDA,antioxidant enzyme activity and s HSPs gene expression in maize leaves and roots.However,the pretreatment with 8-Br-cAMP significantly reduced the increase of heat-induced H₂O₂ and MDA content in leaf and root of maize,but promoted the increase of anti-oxidative defensive enzyme activity and s HSPs gene expression.The results showed that the cAMP pretreatment can improve the anti-oxidative defensive enzyme activity of maize plant under heatstress to remove ROS,which caused the reduce of MDA content,thus improve maize tolerance to heat stress.3 We established transient gene expression and silencing system of maize mesophyll protoplasts to silence adenylate cyclase.The gene expression of adenylate cyclase was significantly inhibited in the protoplasts under heat stress after PEG-mediated 25 μg ds RNA.At the same time,the expression of sHSP26,s HSP16.9 and sHSP17.4 were significantly decreased under heat stress.These results suggest that endogenous cAMP was also involved in the expression of heat-induced s HSPs gene.4 Using 2-DE technology,we identified the proteomics changes of maize leaves under heat stress after pretreatment with exogenous cAMP.For the four treatments,there were 47 proteins with at least 1.5 times changes.Compared to heat stress,the abundance of 29 protein points increased more than 1.5 times,4protein points decreased more than 1.5 times,and 14 protein spots had not obvious changes.Compared without cAMP pretreatment,cAMP pretreatment increased the abundance of 12 protein spots（including s HSP26,s HSP16.9）,decreased the abundance of the 27 protein spots,and had no effect on the abundance of 8 protein spots under heat stress.The GO_pvalue results showed that the most significant biological process influenced by cAMP and heat stress treatment is photosynthesis process,and the cell component is the component in chloroplast.The KEGG analysis results showed that 47 proteins were mainly involved in the signal transduction pathway of metabolic pathway,carbon metabolism and photosynthesis.The further KEGG_pvalue analysis showed that the most significant signal transduction pathway is photosynthesis pathway.Our research results can not only provide a theoretical basis for understanding the role of cAMP and sHSPs in enhancing maize tolerance to heat stress,and is also expected to use s HSPs transgenic technology to produce new maize varieties with outstanding comprehensive resistance,which is helpful to promote the increase of maize production in China.