The Signaling Mechanism Of Nitric Oxide On Ripening And Senescence Of Postharvest Tomato Fruit

Ripening and senescence is the core problem of physiological research after harvest.This process not only led directly to consumption of energy and material,but also led to the decline of quality during storage,and was connected with with others post-harvest loss such as disease.There are many problems to be explained in the deep mechanism on its occurrence,development and the mode of regulation.It is of great significance that clarify these problems to explore and improve the technology of storage fruits and vegetables,reduce the loss after post-harvest,and improve the commercial added value of fresh fruits and vegetables.Nitric oxide(NO)is a small signaling molecule that has the potential to regulate the ripening and senescence of fruits.This paper study the effects of nitric oxide donor(sodium nitroprusside,SNP)and nitric oxide synthesis inhibitor(N-omega-nitro-L-arginine,L-NNA)on the ripening and senescence of Lichun tomato fruit.This study reported the effect of ripening and senescence process,glycometabolism,respiratory metabolism,energy balance,reactive oxygen metabolism and endogenous hormone,while reported that ethylene is involved in nitric oxide adjusting ripening and senescence of fruits tomato fruit.Main results for this study are as follows:1.SNP effect tomato fruits at mature green stage and break stage.High concentrations treatment of SNP(>0.5mm)have promoted significantly ripening and senescence of tomato fruit.Low concentrations treatment of SNP(<0.2mm)have inhibited significantly ripening and senescence on fruit at mature green stage,but have promoted significantly ripening and senescence on fruit at break stage.Both treatments had no effect on the fruit after the onset of respiratory climacteric.2.Using 0.1 mM SNP treatment and 0.1 mM L-NNA treatment on postharvest mature green II stage tomato as the research model,research the NO regulation of ripening and senescence of tomato fruit,and the experiments results show that:(1)Using 0.1 mM SNP treated Lichun tomato fruits,the average break stage of Lichun tomato fruits was delayed by 58 h,the activity of sucrose phosphate synthase(SPS)and sucrose synthetase(SS)ware maintained,the activity of acid invertase(AI)and neutral invertase(NI)were inhibitedafter after climacteric of fruits,product of sugar metabolites were accumulated and consumed more slowly.In Above treatment,the fruit respiration peak,and induced the anti-cyanide respiration of the fruits were stimulated of in 0-24 h after treatment,the respiration climacteric of the fruit during storage was delayed,softening and change color of fruit were inhibited,the production and accumulation of ROS were reduced,the ability of reactive oxygen scavenging was improved,the accumulation of malondialdehyde and the ion permeability were reduced in the later stage of storage.In same treatment,SlMAPK1/2/3 and SlIACS2 expression were stimulated in 0-24 h after treatment,the respiration.However,the peak of ethylene jump and SIACS2 peak were delayed,and the ethylene peak and SIACS2 peak expression were reduced.Using 0.1 mM SNP treated tomato fruits of transgenic antisense SIACS2,the consumption of soluble sugar were Inhibited,softening and color change of fruits was inhibited,the production and accumulation of ROS were reduced,the ability of reactive oxygen scavenging was improved,the accumulation of malondialdehyde and the ion permeability were reduced in the later stage of storage and respiration intensity of fruits was inhibited.There is not Respiratory climacteric in tomato fruits of transgenic antisense SlACS2.(2)Using 0.1 mM SNP treated Lichun tomato fruits,the average break stage of Lichun tomato fruits was delayed by 99 h,the activity of sucrose phosphate synthase(SPS)and sucrose synthetase(SS)ware maintained befor respiratory climacteric,but the activity of acid invertase(AI)and neutral invertase(NI)were increased after climacteric of fruits,product of sugar metabolites were accumulated more slowly but were consumed more faster.In Above treatment,the fruit respiration peak and induced the anti-cyanide respiration of the fruits were inhibited of in 0-24 h after treatment.The respiration climacteric of the fruit during storage was delayed,but were falling fast relative to the control group.In same treatment,SIMAPK1/2/3 and SlACS2 expression were inhibited in 0-24 h after treatment,the peak of ethylene jump and SlACS2 peak were delayed,however the ethylene peak and SlACS2 peak expression were significantly increase relative to the control group.In this tretmente,softening and color change of fruit were accelerated,the production and accumulation of ROS were increased,the ability of reactive oxygen scavenging was reduced,the accumulation of malondialdehyde and the ion permeability were increase after respiratory climacteric.Using 0.1 mM L-NNA treated tomato fruits of transgenic antisense SlACS2,The aboce effects did not exist.(3)Using 0.1 mM SNP combined with 10μM MAPK inhibitor U0126,the effect on ethylene signal and SlACS2 expression.by SNP induced was lifted.The above results show that NO was able to regulate the ripening and senescence of tomato fruit,and nitric oxide synthase(NOS)pathway plays an important role in this process,inhibition fruits ripening of 0.1mM SNP depend on SlACS2 and inhibition fruits senescence of tomato did not depend on SIACS2.The 0.1mM L-NNA inhibited the ripening of fruits but accelerates senescence of fruits,and the effect depends on.SlACS2.SlACS2 is the key point of NO regulation on ripening and senescence of tomato fruits,and MAPK involved in regulation of NO on ethylene sign.