Abstract
Strawberry fruits are rich in flavonoids like proanthocyanidins and anthocyanins. Their biosynthesis and accumulation are controlled by the MYB-bHLH-WD40 (MBW) transcriptional complex, which is mainly formed by basic helix-loop-helix (bHLH) and MYB transcription factors (TFs). In Arabidopsis thaliana both bHLH and MYB TFs are repressed by JASMONATE ZIM-DOMAIN (JAZ) proteins, the key repressors of the jasmonate-signaling pathway. The aim of this research was the characterization of the FaJAZ1/8.1/9/10 proteins and molecular targets of signaling components and anthocyanin biosynthesis-related TFs of Fragaria × ananassa by protein–protein interactions. For this, domain compositions were studied by multiple alignments and phylogenetic analyses, while interactions were analyzed by yeast two-hybrid (Y2H) assays. We detected high conservation of FaJAZ proteins and jasmonate-signaling components, as well as FabHLHs and FaMYB10 TFs. Moreover, we report the F. × ananassa YABBY1 (FaYAB1) TF, which is related to anthocyanin biosynthesis in Arabidopsis, showed high conservation of functional domains. We demonstrated that FaJAZ repressors interacted with F. × ananassa NOVEL INTERACTOR OF JAZ (FaNINJA), FaMYC2, and JASMONATE ASSOCIATED MYC2-LIKE (FaJAM) proteins. Besides, transcription factors of MBW-complex like FabHLH3, FabHLH33, and FaMYB10, together with FaYAB1, were molecular targets of FaJAZ repressors, exhibiting specificity or redundancy of interaction depending on particular FaJAZ protein. Overall, these results suggest that interactions of jasmonate-signaling components are fully conserved, and anthocyanin biosynthesis might be regulated by JAZ repressors in F. × ananassa.
Highlights
Fleshy fruits of cultivated strawberry (Fragaria × ananassa Duch.) are highly valued by its taste, flavor, red color, and their multiple nutritional properties [1]
These results suggest that interactions of jasmonate-signaling components are fully conserved, and anthocyanin biosynthesis might be regulated by JASMONATE ZIM-DOMAIN (JAZ) repressors in F. × ananassa
Many aspects of the metabolism and biochemical pathways of the anthocyanin biosynthesis are well known during the development of strawberry fruits, the knowledge about the role of some molecular pathways regulating its biosynthesis is still scarce
Summary
Fleshy fruits of cultivated strawberry (Fragaria × ananassa Duch.) are highly valued by its taste, flavor, red color, and their multiple nutritional properties [1]. The nutritional value is given by flavonoid compounds like anthocyanins, which are in large amounts in red fruits [2] and have different benefits for human health [1]. Ripe strawberry fruits are rich in anthocyanins, which are synthesized from leucoanthocyanidins by the sequential activity of anthocyanidin synthase (ANS) and uridine diphosphate (UDP) glucose:flavonoid 3-O-glucosyl transferase (UFGT) enzymes [6,18]. These enzymes are under transcriptional control of the MBW-complex constituted by R2R3-MYB, basic helix-loop-helix (bHLH), and WD40 repeats transcription factors (TFs) [9,18]. Two MBW complexes regulate differentially the expression of the genes encoding for the catalytic enzymes of PAs and anthocyanins biosynthesis [6,9,18]
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