ABCC transporters mediate the vacuolar accumulation of crocins in saffron stigmas

Abstract

Compartmentation is a key strategy enacted by plants for the storage of specialized metabolites. The saffron spice owes its red color to crocins, a complex mixture of apocarotenoid glycosides that accumulate in intracellular vacuoles and reach up to 10% of the spice dry weight. We developed a general approach, based on coexpression analysis, heterologous expression in yeast (Saccharomyces cerevisiae), and in vitro transportomic assays using yeast microsomes and total plant metabolite extracts, for the identification of putative vacuolar metabolite transporters, and we used it to identify Crocus sativus transporters mediating vacuolar crocin accumulation in stigmas. Three transporters, belonging to both the multidrug and toxic compound extrusion and ATP binding cassette C (ABCC) families, were coexpressed with crocins and/or with the gene encoding the first dedicated enzyme in the crocin biosynthetic pathway, CsCCD2. Two of these, belonging to the ABCC family, were able to mediate transport of several crocins when expressed in yeast microsomes. CsABCC4a was selectively expressed in C. sativus stigmas, was predominantly tonoplast localized, transported crocins in vitro in a stereospecific and cooperative way, and was able to enhance crocin accumulation when expressed in Nicotiana benthamiana leaves.

Chitosan Application in Vineyards (Vitis vinifera L. cv. Tinto Cão) Induces Accumulation of Anthocyanins and Other Phenolics in Berries, Mediated by Modifications in the Transcription of Secondary Metabolism Genes

“…The tonoplast transporters (ABCC1 and MATE1), and GST were observed increasingly upregulated in grape berries upon kaolin foliar application towards improved anthocyanin accumulation in berry skins [27]. Recently, the roles of ABCC and MATE transporters in vacuolar accumulation of specific metabolite crocins in saffron stigmas were characterized [28]. Glutathione S-transferase (GST) tends to express only in berries and facilitates the conjugation of anthocyanins with reduced glutathione and transports them to the vacuoles [29].…”

Diurnal metabolic regulation of isoflavones and soyasaponins in soybean roots

“…A glucosinolate transporter 1 (GTR1) in Arabidopsis was identified as jasmonoyl-isoleucine and gibberellin transporter based on its co-expression with jasmonate biosynthetic genes (Saito et al, 2015). Furthermore, Catharanthus roseus CrNPF2.9 was identified by co-expression analysis of the biosynthetic genes of monoterpene indole alkaloids (Payne et al, 2017), and saffron ( Crocus sativus ) CsABCC4a was revealed as a transporter for crocins by narrowing down the candidate transporter genes that were highly expressed in pistils (Demurtas et al, 2019). These reports prompted us to genetically and biochemically investigate candidate transporter genes for isoflavone and soyasaponin transport further.…”

Carotenoid biofortification in crop plants: citius, altius, fortius

“…Strigolactone translocation in petunia and vacuolar sequestration of crocins in saffron are mediated by ABC transporters [113,114].…”