The Research On The Function Of Endogenous Melatonin In Arabidopsis Infected By Pathogens

Melatonin is an effective bioactive molecule in plants.The three synthetase,ASMT,COMT and SNAT,have been implicated in the the last two steps of synthesis of melatonin in plants.It has been shown to be able to participate in a variety of biotic and abiotic stresses,but relatively few studies of endogenous melatonin resistance to pathogen.The artificial mi RNA technology was uesd to silencing of melatonin synthase genes ASMT,COMT and SNAT.We selected that asmt-1,asmt-2,snat-1 and snat-2 transgenic lines for resistance experiments by detecting the expression of endogenous genes and the content of melatonin in transgenic plants.This research focused on wild-type Arabidopsis,gene silencing lines(asmt-1,asmt-2,snat-1,and snat-2)and overexpressed Arabidopsis lines(ASMT-OE-1,ASMT-OE-2,SNAT-OE-1 and SNAT-OE-2)which made by our laboratory as materials.The effects of endogenous melatonin on plant resistance to pathogen are discussed in the following two parts.The main conclusions are as follows:1.Effects of endogenous melatonin on plants infected by Botrytis cinerea.The research has shown that ASMT-overexpression lines and SNAT-overexpression lines lead to up-regulate the expression of resistance genes PR1,PR5 and the transcription factor gene WRKY33,up-regulate jasmonic acid(JA)defense pathway marker gene PDF1.2,and down-regulate the expression of the transcription factor gene MYC2 in the JA signaling pathway,enhance the activity of antioxidant enzymes(SOD and POD),increase the content of JA,alleviate plant disease symptoms,and reduce lesion sizes of leaves by increasing the content of endogenous melatonin.These results indicate that melatonin improves the resistance of plants to Botrytis cinerea.At the same time,gene silencing lines showed the opposite trend,which showed susceptible to Botrytis cinerea.2.Effects of endogenous melatonin on systemic acquired resistance(SAR).Plants were treated with different Pseudomonas syringae(Psm avr Rpm1 and Psm ES4326).The research has found that ASMT-overexpression lines and SNAT-overexpression lines that induce to increase the content of melatonin,up-regrate the expression of related resistance genes(PR1,ALD1 and FMO1),increase the content of salicylic acid(SA),reduce the number of bacterial number,and alleviate the symptoms of leaf disease,which indicate that melatonin contributes to SAR.Gene silencing lines suppresses the generation of SAR.In conclusion,our findings evaluated the transgenic plants with the melatonin biosynthetic gene to determine the role of plant melatonin after the treatment of Botrytis cinerea and Pseudomonas syringae.Melatonin could be used as an effective regulator of plant stress resistance in genetic level.At the same time,our results indicate that the related signal transduction pathways and the interaction between melatonin and other plant hormones.Our results provide a theoretical basis for plant stress resistance research.