Study On The Relationship Between Lycopene Biosynthesis,soften And NAC Transcription Factor In Tomato

NAC(NAM,ATAF1/2and CUC2),regarded as plant-specific transcription factors with multi-biological functions,was reported involving in regulation of plants growth,maturing and senescence.In this research,virus-induced gene silencing(VIGS)method was employed to explore the possible regulation function of SNACs in tomato lycopene biosynthesis and soften related genes by silencing SNAC4-9 in Micro-Tom tomato fruits.The main results were briefed as follows:1.VIGS research analysis.The plants were suffered through injection of GV3101 Agrobacterium tumefaciens bearing pTRV1,pTRV2 and pTRV2-SNAC4-9.After agrobacterium infection,all the SNACs-silenced fruits exhibited a series of maturation delayed phenotypes.In specifics,the effects on SNAC4 and SNAC9 silencing fruits were significant.2.The physiology and biochemical analysis indicated that SNACs silencing resulted in plently changes such as dramatic delay of the onset of ripening,low respiration rate,reduced pigment accumulation and declined climacteric ethylene production,thus leading to yellow or orange matured fruits.In addition,silencing of SNAC4 and SNAC9 resulted in different softening patterns.3.The test results of transcription level of the carotene metabolism showed that SNACs silencing influenced the accumulation of lycopene in tomato fruits.In specifics,the silenced SNACs genes expression inhibited the transcription of lycopene biosynthesis genes PSY1,PSY2,PDS,ZDS,ZISO,CRTISO,but promoted the expression of ?-LCY and ?-LCY genes,leading to a more decomposition of lycopene into carotenoids.This process also caused the absent presentation of normal reddening maturation phenotypes.The transcription of ethylene synthesis genes ACS2,ACS4,ACO1 and ethylene receptor gene ETR4 and NR were also declined,inhibiting the fruit ripening.4.The detected results of softening metabolic showed that,silencing of SNAC4 inhibited expression of softening related genes such as EXP,LOX,PG and PL and suppressed the related enzyme activities significantly.Silenced SNAC9 promoted the softening of tomato fruit,but softening of the SNAC5/6/7-silenced fruits were not significantly changed.5.Exogenous hormones were used to treat the SNACs silenced fruits during the breaker stage.Ethephon treatment led to the accumulation of lycopene in tomato fruit.Treatment of ABA accelerated the softening process of SNAC4 silenced fruits,while NDGA treatment retarded the SNAC9 silenced softening.It's showed that SNACs were associated with ABA in regulating tomato softening metabolism.