Carotenoids Components And Biosynthesis Genes Analysis In Tagetes Erecta

Tagetes erecta has high nutritional and economic value due to the synthesis and accumulation of huge amounts of carotenoids in its flowers,but the underling molecular mechanism and genetic resources remain unclear.In this present work,the contents of four carotenoids(lutein,zeaxanthin,lycopene and β-carotene)and a flavonoid(rutin)at four developmental stage flowers of different color marigold cultivars,‘Quanwang’(yellow flower),‘Taishang’(yellow-orange flower)and ‘Juwang’(orange flower),were determined by high performance liquid chromatography.The results indicated that lutein was the most abundant component among the carotenoids but exhibited significantly different abundance in marigold with varied colors,and showed the highest content in orange flower Tagetes erecta.For rutin,the contents indicated similar trends in three color marigolds at four developmental stages,and the distribution in different flowers was relatively uniform.Meanwhile,the effect of heating drying on lutein content was evaluated.The results showed that mature marigold flowers were more sensitive to heat treatment to cause more lutein loss.Furtherly,the expression levels of twelve genes(TePSY1,TePSY2,TePSY3,TePDS,TeZDS,TeLCYE,TeLCYB,TeCHY,TeCCD1 a,TeCCD1 b,TeCCD4,TeNCED2)in the carotenoids biosynthesis pathway of three color marigolds at four developmental stages were quantified using q RT-PCR.The resulting expression of upstream genes such as TePSY,TePDS and TeLCYE in the highest carotenoids containing orange marigold were remarkably higher than those in lower pigments yellow-orange and yellow varieties.Furthermore,the levels of TeCCD family genes involved in downstream degradation of carotenoids remained low throughout the development of high pigments orange flowers.The transcriptional variance in the carotenoids metabolic pathway genes contributed to the difference in the synthesis and accumulation of pigment,and thus the diverse coloration of marigold flowers.The expression analysis suggested that TePDS(Tagetes erecta phytoene desaturase)is an important upstream gene in carotenoids biosynthesis pathway.To verify its function,molecular cloning,vector construction and tomato genetic transformation of TePDS were carried out,and the transgenic lines specifically expressed TePDS in fruits were obtained.Phenotypic analysis showed that the introduction of TePDS accelerated fruit color change compared with wild type tomato,and the contents of lycopene,lutein,β-carotene and zeaxanthin significantly increased in the transformed fruits.However,there were no obvious adverse effects on the growth and development of tomato plants,flowering time,fruit weight and size,and the development of fruit and seed.The performance of marigold TePDS confirmed its function and potential application in genetic improvement of fruit pigments nutrient quality in crops.Taken together,this study analyzed the pigments composition and corresponding expression differences of carotenoids biosynthesis genes during marigold flower coloration to provide research basis for further investigation on the molecular mechanism and new gene resource for crop fruit traits improvement.