ABI5 regulates ABA-induced anthocyanin biosynthesis by modulating the MYB1-bHLH3 complex in apple

Abstract

Abscisic acid (ABA) induces anthocyanin biosynthesis in many plant species. However, the molecular mechanism of ABA-regulated anthocyanin biosynthesis remains unclear. As a crucial regulator of ABA signaling, ABSCISIC ACID-INSENSITIVE5 (ABI5) is involved in many aspects of plant growth and development. Nevertheless, whether ABI5 regulates anthocyanin biosynthesis has not been reported. In this study, we found that MdABI5, the homolog of Arabidopsis ABI5, positively regulated ABA-induced anthocyanin biosynthesis in apple. A series of biochemical tests showed that MdABI5 specifically interacts with MdbHLH3, a positive regulator of anthocyanin biosynthesis. MdABI5 enhanced the binding of MdbHLH3 to its target genes MdDFR and MdUF3GT. In addition, MdABI5 directly bound to the promoter of MdbHLH3 to activate its expression. Moreover, MdABI5 acted as an enhancer in the ABA-promoted interaction between MdMYB1 and MdbHLH3. Finally, antisense suppression of MdbHLH3 significantly reduced anthocyanin biosynthesis promoted by MdABI5, indicating that MdABI5-promoted anthocyanin biosynthesis was dependent on MdbHLH3. Taken together, our data suggest that MdABI5 plays a positive role in ABA-induced anthocyanin biosynthesis by modulating the MdbHLH3-MdMYB1 complex. Our work enriches the functional studies of ABI5 and further broadens the regulatory network of ABA-mediated anthocyanin biosynthesis, providing new insights for further study of the transcriptional regulatory mechanisms of anthocyanin biosynthesis.

Red and blue light treatments of ripening bilberry fruits reveal differences in signalling through abscisic acid‐regulated anthocyanin biosynthesis

“…Abscisic acid (ABA), which is synthesized by the key cleavage enzyme 9‐ cis ‐epoxycarotenoid dioxygenase (NCED) in apocarotenoid pathway, has been shown to be a major regulator of ripening in non‐climacteric fruits, such as strawberry, grapes and bilberry (Ferrara et al, 2015; Jia et al, 2011; Karppinen, Tegelberg, Häggman, & Jaakola, 2018) and in climacteric fruits, such as apple (An et al, 2021). The ABA signal transduction is known to be mediated by pyrabactin resistance/like (PYR/PYL) receptors and ABA‐responsive element‐binding factors (ABFs) through SQUAMOSA‐MADS box (TDR‐type) TFs leading to regulation of the MBW complex proteins (Chung et al, 2019).…”

Integrated analysis of the transcriptome, sRNAome, and degradome reveals the network regulating fruit skin coloration in sponge gourd (Luffa cylindrica)

“…The bHLH proteins form one of the largest transcription factor families in plants. The anthocyanin biosynthesis-related SGIIIf bHLH genes have been identified in horticultural crops, including those encoding bHLH3 and bHLH64 transcription factors in apple and pear 58 , 59 . The R2R3-MYB transcription factor genes SlAN2-like and BrPAP1a encode regulators of anthocyanin production in tomato and turnip 60 , 61 .…”

Pigmentation and Flavonoid Metabolite Diversity in Immature ‘Fuji’ Apple Fruits in Response to Lights and Methyl Jasmonate

“…Arakawa et al [26] reported that a rapid increase in anthocyanin synthesis occurred in detached apples after 24 h of light exposure. Further, higher light intensity was reported to induce higher anthocyanin biosynthesis in apples [28]. Although the results of postharvest qualities revealed no significant damages (Table 1) following treatment with a UV-B intensity of 2.1 W•m −2 •S −1 , determining an appropriate light intensity and the duration of irradiation to achieve certain levels of red pigmentation is still required.…”