Phytochrome interacting factor MdPIF7 modulates anthocyanin biosynthesis and hypocotyl growth in apple

Abstract

Light affects many physiological and developmental processes of plants by regulating the expression and activity of light responsive proteins. Among them, phytochrome interacting factors (PIFs) play pivotal roles in the regulation of anthocyanin accumulation and hypocotyl growth. However, the molecular mechanism is not well understood, especially in woody plants, such as apple (Malus × domestica). In this study, we identified a light responsive PIF protein, MdPIF7, in apple and investigated the molecular mechanism of its regulation of anthocyanin biosynthesis and hypocotyl growth. We found that overexpression of MdPIF7 decreased anthocyanin accumulation in transgenic apple materials and promoted hypocotyl elongation in ectopically expressed Arabidopsis (Arabidopsis thaliana). Further investigation showed that MdPIF7 functioned by interacting with B-box 23 (MdBBX23), a positive regulator of anthocyanin biosynthesis in apple and hypocotyl growth inhibition in ectopically expressed Arabidopsis, and attenuating the transcriptional activation of MdBBX23 on LONG HYPOCOTYL 5 (MdHY5). In addition, MdPIF7 interacted with basic region leucine zipper 44 (MdbZIP44) and ethylene response factor 38 (MdERF38), two positive regulators of anthocyanin biosynthesis, and it negatively regulated MdbZIP44- and MdERF38-promoted anthocyanin accumulation by interfering with the interaction between MdbZIP44/MdERF38 and MdMYB1. Taken together, our results reveal that MdPIF7 regulates anthocyanin biosynthesis in apple and hypocotyl growth in ectopically expressed Arabidopsis through MdPIF7-MdBBX23-MdHY5 and MdPIF7-MdbZIP44/MdERF38-MdMYB1 modules. Our findings enrich the functional studies of PIF proteins and provide insights into the molecular mechanism of PIF-mediated anthocyanin biosynthesis and hypocotyl growth.

The regulatory module MdBZR1–MdCOL6 mediates brassinosteroid‐ and light‐regulated anthocyanin synthesis in apple

“…Significant progress has been made in the characterization of the molecular mechanisms by which external stimuli or endogenous hormones regulate fruit anthocyanin synthesis. For example, BBX TFs form multiple modules, including BBX–HY5 and BBX–PIFs, which regulate anthocyanin synthesis induced by light signals (Fang et al ., 2019; Song et al ., 2020; Liu et al ., 2022). Moreover, BZR1, which is a key component of the BR signaling pathway, is crucial for BR‐regulated fruit quality‐related processes, including ripening and softening (Shan et al ., 2020; He et al ., 2021; Ji et al ., 2021).…”

“…The amplified MdBZR1 and MdCOL6 fragments were inserted into the pFAST‐R03 vector to generate RNAi suppression vectors. The apple leaf coloration assays were performed as previously described (Liu et al ., 2022). The detached apple leaves were placed on subculture medium containing BL and exposed to HL conditions (photon flux density: 300 μmol m −2 s −1 ).…”

MdVQ10 promotes wound‐triggered leaf senescence in association with MdWRKY75 and undergoes antagonistic modulation of MdCML15 and MdJAZs in apple

“…The luciferase complementation imaging assay was performed in tobacco leaves as described previously (Liu et al., 2022). The full‐length coding sequences of MdVQ10 and MdWRKY75 were cloned into the pCAMBIA1300‐nLUC and pCAMBIA1300‐cLUC vectors, respectively.…”

PIF8‐WRKY42‐mediated salicylic acid synthesis modulates red light induced powdery mildew resistance in oriental melon

“…PIFs interact with MYC2 to integrate light and jasmonic acid signalling pathways, regulate the transcription of terpene synthase genes, and promote the rapid spread of arboviruses (P. Zhao et al, 2021), PIF4/5 negatively regulates plant defence response to B. cinerea by directly binding to the ERF1 promoter to inhibit its expression (Xiang et al, 2020). There are eight PIFs in Arabidopsis thaliana , among which the functions of PIF1‐7 have been studied, such as in seed germination (Kim et al, 2008), seedling growth (Hornitschek et al, 2012), hypocotyl elongation (Liu et al, 2022), anthocyanin biosynthesis (Shin et al, 2007), thermal morphogenesis (Lee et al, 2021), shading (Paulišić et al, 2021), fruit development (R. Zhang et al, 2019), chlorophyll synthesis (Job & Datta, 2020; Monte et al, 2004) and senescence (Sakuraba et al, 2014; Song et al, 2014), abiotic stress (Gao et al, 2018; He et al, 2016; F. Wang, Chen, et al, 2020; P F. Zheng et al, 2021) and biotic stress (P. Zhao et al, 2021; Y. Zhao et al, 2014). However, the functions of PIF8 have been rarely reported except for three recent reports (Oh et al, 2019; Saud et al, 2022; Y. Zhang et al, 2021).…”

“…Although several WRKYs have been identified as key regulators of disease resistance, transcriptional regulation upstream of WRKYs remains unclear. Additionally, two recent reports suggest that WRKY2 and WRKY10 are involved in plant photomorphogenesis through interaction with phyB (S. Wang et al, 2022); light signalling protein FHY3 directly binds to the WRKY28 promoter and inhibits its transcription, thereby negatively regulating leaf senescence (Tian et al, 2020). However, limited information is known whether WRKY is involved in the integration of light signal and SA signal to enhance powdery mildew resistance of oriental melon.…”