Abstract
Flavonoids play multiple roles in plant coloration and stress resistance and are closely associated with human health. Flavonoids and non-flavonoids (such as phenolic acids) are produced via the phenylpropanoid-derived pathway. Anthocyanidin synthase (ANS) catalyzes the synthesis of anthocyanins from leucoanthocyanidin in the flavonoids branched pathway. In this study, SmANS from Salvia miltiorrhiza was cloned and mainly localized in the endoplasmic reticulum (ER), plastids, Golgi, plasma membrane, and nucleus of tobacco epidermal cells, and was most highly expressed in purple petals in S. miltiorrhiza, whereas it showed almost no expression in white petals, green calyxes, and pistils in S. miltiorrhiza Bge f. alba. Overexpressed SmANS enhanced anthocyanin accumulation but reduced salvianolic acid B (SAB) and rosmarinic acid (RA) biosynthesis in S. miltiorrhiza and S. miltiorrhiza Bge f. alba plantlets, meanwhile, it restored the purple-red phenotype in S. miltiorrhiza Bge f. alba. These changes were due to reallocation of the metabolic flow, which was influenced by the SmANS gene. These findings indicate that SmANS not only plays a key role in anthocyanin accumulation in S. miltiorrhiza, but also acts as a “switch” for the coloration of S. miltiorrhiza Bge f. alba. This study provides baseline information for further research on flavonoids metabolism and improvement of anthocyanin or phenolic acid production by genetic engineering.
Highlights
Salvia miltiorrhiza Bunge (Danshen), which has purple flowers, is a traditional medicinal model plant with great medicinal and economic value, as well as an efficient genetic transformation system [1]
The main effective compounds in Danshen medicinal materials are lipophilic tanshinones and hydrophilic phenolic acids, such as salvianolic acid B (SAB) and rosmarinic acid (RA) [3], abundant flavonoids components are distributed in their aerial parts [4]
Since SmANS expression levels were limited in the white flowers and green calyxes of S. miltiorrhiza Bge f. alba, we propose that SmANS is a switch on anthocyanin biosynthesis in S. miltiorrhiza and S. miltiorrhiza Bge f. alba plantlets
Summary
Salvia miltiorrhiza Bunge (Danshen), which has purple flowers, is a traditional medicinal model plant with great medicinal and economic value, as well as an efficient genetic transformation system [1]. Flavonoids are the major pigments responsible for the coloration of plant flowers, leaves, stems, fruits, and other organs [5] They have been classified into different subgroups, including anthocyanin, proanthocyanidins, flavones, flavonols, flavanones, aurones, and isoflavones. ANS, which is one of the key enzyme genes downstream of the flavonoids-branched pathway, and catalyzes the transformation of leucoanthocyanidin to colored anthocyanidin before the final glycosylation steps, has been well studied in many plants, but not in S. miltiorrhiza [22,23,24,25]. In view of the extremely important roles of ANS in plants, it is necessary to survey the functional mechanism of this gene, and its role in the regulation of other non-flavonoids branched metabolic pathways in S. miltiorrhiza. ThehteesreogreesnuelotsussugSg. emstiltthioartrhSimzaANBSgeis fn.otalobna,lyraeskpeeycteinvzeylym, emgeeannewthhailtecoint trroelsstothreedputrhpelepcuorloprlea-trioedn opfhtehneotayeprieaol fpSa.rtmiinltSio.rmrhiilztaioBrrgheizfa.,ablbuat pallasontalecttss. aTshaessewrietcsuhltths asturgegsetsritctthsaatnStmhoAcNyaSniisnnaoctcuomnluylaatkioeny aennzdypmuerpgleenecotlhoartactioonntrionlsSt.hme ipltuiorrprlheizcaolBograetifo. nalobaf twhehiateerpiaeltpalasrtainndSg. rmeielntiocrarhlyizxae,sb, utht ualssopraocvtsidaisnga vswaliutcahbletheavtidreesntcreicftosratnhtehmocoylaencuinlaarcrceugmuluatlaotriyonmeacnhdanpiusrmploef ctholeoaranttihooncyinanSin. mbiilotsioyrnrhthizeaticBgpeatfh.walabya, awshwiteellpaestathlse carnodsstgarlekebnetcwaleyexnesfl,atvhounsoipdrsoavniddinpghevnaolluicabalceidemviedteanbcoelisfmor inthSe. mmioltlieocrurhlaizra.regulatory mechanism of the anthocyanin biosynthetic pathway, as well as the crosstalk between flavonoids 2a.ndRepshuelntsolic acid metabolism in S. miltiorrhiza
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