Capsaicin Accumulation And Expression Analysis Of Biosynthesis-related Genes During Pepper Fruit Development

Pepper plays an indispensable role in life, production and scientific research,which is mainly related with the capsaicinoids. Capsaicin has been widely used, butthe capsaicin synthesis and expression regulation of gene is not clear. In ourresearch,there were three different types pepper fruits,2012-2(belongs to Capsicumfrutescens L.type), Chaotian pepper (belongs to Capsicum annuum L. type) andHuangdenglong pepper (belongs to Capsicum chinense Jacq. type) in different stagesand different time after JA treatment for capsaicin biosynthetic pathway geneexpression analysis and capsaicin content analysis.Different stages of gene expression analysis showed:2012-2:(I) branched chainof vanilla amine, PAL and4CL gene expression decreased at first and then increased,PAL gene in mature stage was the lowest,expression levels elevated after mature stage;4CL at the colour-changed stage was the lowest, increased after colour-changedstage.Bear fruit stage to mature-green stage,C4H, HCT, COMT and pAMT expressionlevel was elevated to the highest, C4H, HCT and pAMT has been reduced aftermature-green stage, COMT slightly increased after mature stage;(II) branched chainof fatty acids,bear fruit stage to colour-changed stage,BCAT expression increased tothe highest, colour-changed stage to mature stage decreased,the expression of BCATincreased after mature stage;bear fruit stage to colour-changed stage, the expression ofFatA increased at first and then decreased, colour-changed stage to over-mature stageincreased and decreased also;(III) Pun1gene in bear fruit stage to mature green stageincreased expression, mature green stage to colour-changed stage reduced to a verylow level, maintained at a low level after the colour-changed stage.Bear fruit stage tomature-green stage, expression of POD decreased slightly, mature-green stage tocolour-changed stage increased,while colour-changed stage to over-mature stage wasreduced to a very low level.Chaotian pepper:(I) branched chain of vanillyl amine, bear fruit stage to colour-changed stage, PAL, C4H,4CL, HCT and COMT gene expression increased atfirst and then decreased, mature-green stage was the highest, colour-changed stage tomature period,PAL and COMT genes unchanged, the exression increased after maturestage. C4H and HCT changed little after colour-changed stage. After colour-changedstage the expression of4CL gene continue rised to last;Bear fruit stage tocolour-changed stage pAMT expression increased to the highest, colour-changed stageto mature stage reduced to the lowest expression, mature stage to over-mature stageexpression increased;(II) branched chain of fatty acids,bear fruit stage tocolour-changed stage BCAT expression increased to the highest, colour-changed stageto mature stage decreased, increased after mature stage;bear fruit stage tomature-green stage expression of FatA increased to the hightest; and mature-greenstage to colour-changed stage decreased, mature stage to over-mature stage increasedand decreased again;(Ⅲ)Bear fruit stage to mature-green stage, the expression ofPun1gene increased, mature-green stage to colour-changed stage maintain a highlevel, colour-changed stage to mature stage expression of gene decreased, andexpression increased after mature stage.Bear fruit stage to mature-green stage PODdecreased expression, mature-green stage to the colour-changed stage increased,colour-changed stage to over-mature stage express low.Huangdenglong pepper:(I) branched chain of vanillyl amine,Bear fruit stage tothe colour-changed stage,PAL, C4H,4CL, HCT and COMT gene expression increasedfirst and then decreased, mature-green stage was the highest, colour-changed stage tomature stage,PAL, C4H,4CL and COMT unchanged; HCT gene expression continueto rise after colour-changed stage;Bear fruit stage to colour-changed stage, pAMTexpression increased to the highest, and after colour-changed stage continued toreduce;(II) branched chain of fatty acids,Bear fruit stage to mature stage, BCAT wasfirst increased and then decreased, the highest expression was in mature green stage,mature stage to over-mature stage unchanged; bear fruit stage to mature green stage,FatA increased to the highest, and after mature green stage declined;(III)Bear fruitstage to colour-changed stage the expression of Pun1gene was increased,andcolour-changed stage to mature stage decreased, after mature stage was slightly reduced.Bear fruit stage to mature green stage, POD gene decreased expression,mature-green stage to mature stage rised, and after mature stage decreased expression.Analysis of five stages of capsaicin content in pepper fruits showed, in2012-2pepper fruits, capsaicin content has been increased constantly,bear fruit stage tomature stage in Chaotian pepper and Huangdenglong pepper, capsaicin contentincreased straightly, while decreased after the mature stage.Treatment of pepper fruits in mature-green stage with JA, after4h,12h,24h and48h, using Real-time RT-PCR analysis showed capsaicin biosynthetic gene inChaotian pepper was sensitive to JA, most of the genes increased the expression.partof the biosynthesis-related gene in2012-2changed slightly after JA treatment in theearly, increased soon after, the other changed wavily.while majority of gene inHuangdenglong pepper decreased after treatment.In Chaotian pepper capsaicin content increased with JA treated compared withcontrol group, and10d after treatment, content of capsaicin declined both in treatmentgroup and control group, but the treatment group was significantly higher than thecontrol group of about1/6; In2012-2and Huangdenglong pepper,the capsaicincontent in treatment group and control group reached to maximum on the sixth day,and decreased after the six day,capsaicin in treatment group were higher than controlgroup,Treatment group of2012-2to15d was higher than control group about1/3,while Huangdenglong pepper at15d treatment group slightly higher than control.A pair of primers were designed,through PCR amplification,three types pepperacyltransferase gene Pun1(GenBank:AY819029) upstream sequence of1900bp wereobtained, the promoter prediction analysis of2012-2and Chaotian pepper containingTATA-box, CAAT-box, P-box, ABRE, TCA, MBSI, WUN-motify, HSE elements,TATC-box, Box-W1, MBS and TC-rich repeats. Huangdenglong pepper containsC-repeat/DREbut lack Box-W1.