Mechanism Of Methionine Lyase/Synthetase In Regulating Tomato Fruit Ripening And Senescence

Tomato(Solanum lycopersicum),also known as tomato,is a plant belonging to Solanaceae.It has been widely cultivated in the world as edible fruits and vegetables.Tomato fruit is rich in nutrition and vitamin C.Tomato is a respiratory climacteric fruit.There have been many studies on delaying ripening,senescence and decay of Postharvest Tomato Fruit,but the internal regulation mechanism of ripening and senescence of tomato fruit is still unclear.Tomato fruits are regulated by many signals during ripening.Some studies have shown that the ripening and senescence of postharvest fruits are affected by ethylene.Methionine is an indirect precursor of ethylene synthesis.Methionine synthetase(METS)and methionine lyase(MGL)in plants synthesize and decompose methionine respectively,The regulation mechanism of these two enzymes in tomato fruit ripening and senescence is still unclear.50 MGL family members were found in 10 plant species such as tomato,Arabidopsis and sweet potato,and 19 METS gene members were found in 6 plant species such as tomato,Arabidopsis and cucumber.The phylogenetic tree showed that METS in tomato had high homology with METS in sweet potato,and MGL gene in tomato had high homology with some genes in soybean,Arabidopsis and sweet potato,Motif analysis of METS and MGL family showed that motif results were consistent with evolutionary tree results.Genes related to carotenoid synthesis(PSY1,PDS,ZDS),chlorophyll degradation(NYC1?PAO?PPH?SGR1),cell wall metabolism(CEL2?EXP?PG?TBG4?XTH5),ethylene biosynthesis pathway(ACO1?ACO3?ACS2?RIN?E4?E8?Nor)were significantly down regulated,However,MGL gene silencing and METS transient overexpression of tomato fruit showed the opposite phenotype.It was found that sl9240(solyc12g009240.1.1)significantly activated METS activity and Sl240(solyc12g006240.1.1)significantly inhibited Mets activity.Yeast one hybrid experiment was used to verify that the SBP family member(solyc10g018780.1)could bind to the first,third,fourth and fifth gtac sites in the upstream of MGL promoter.VIGS technology was used to find that the tomato fruit was precocious after SBP780 gene silencing.Subcellular localization experiment showed that METS protein was mainly located in the nucleus,The results of yeast two hybrid experiment showed that MGL interacted with the nucleoprotein importin ?3and itself,The interaction between MGL,MGL truncation,MGL mutation and importin ?3 is consistent with the results of yeast two hybrid.In conclusion,we studied the transient high expression and gene silencing of methionine synthetase(METS)and methionine lyase(MGL),and found that METS/MGL played a key role in tomato fruit ripening and development.Yeast two hybrid and luciferase complementary experiments confirmed the relationship between MGL and importin ?3.It provides a theoretical basis for postharvest storage of tomato fruit.