Two B-Box Proteins Regulate Photomorphogenesis by Oppositely Modulating HY5 through their Diverse C-Terminal Domains

Job, Nikhil; Yadukrishnan, Premachandran; Bursch, Katharina; Datta, Sourav; Johansson, Henrik

doi:10.1104/pp.17.00856

Cited by 110 publications

(110 citation statements)

References 56 publications

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“…3,4,5,6,7,8 In our recent study, by taking the examples of BBX21 and BBX24, we have shown that the opposite functions of these proteins are determined by their diverse Cterminal regions. 9 Our findings also indicated that multilayered regulation of HY5 by closely related BBX proteins is the key in mediating their antagonistic actions. This work is aimed at analysing the mechanistic basis of the opposite roles played by BBX21 and BBX24 and discussing some insights that can potentially propel questions for the future.…”

supporting

confidence: 53%

Opposite roles of group IV BBX proteins: Exploring missing links between structural and functional diversity

Yadukrishnan

Job

Johansson

et al. 2018

Plant Signaling & Behavior

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BBX proteins are a family of zinc finger transcription factors that are versatile regulators of plant development. The 32 BBX proteins in Arabidopsis are subdivided into five structural groups based on their domain structure. Members of group IV play important and diverse roles in light-regulated development. The N-terminal B-box domains mediate DNA binding and transcriptional regulation. The C-terminal region determines the functional diversity of the structurally similar group IV members as reported in our recent study investigating the basis of functional diversification between BBX21 and BBX24. We also found that multi-layered regulation of HY5 by the BBX proteins leads to a diverse repertoire of developmental effects. Here we provide a comprehensive structure-function analysis of the group IV BBX proteins.

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supporting

confidence: 53%

Opposite roles of group IV BBX proteins: Exploring missing links between structural and functional diversity

Yadukrishnan

Job

Johansson

et al. 2018

Plant Signaling & Behavior

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“…The B‐box domains play crucial roles in the interactions with other proteins. In Arabidopsis , AtBBX21 (Xu et al ., ), AtBBX22 (Datta et al ., ), AtBBX24 (Job et al ., ) and AtBBX25 (Gangappa et al ., ) physically interact with HY5, and three BBX proteins interact with HOMOLOG OF HY5 through B‐box domains (Gangappa et al ., ). A point mutation in the B‐box domain impedes the interaction with HY5 (Datta et al ., ).…”

Section: Discussionmentioning

confidence: 99%

“…As part of photomorphogenesis, light‐induced anthocyanin accumulation involves several BBX proteins. AtBBX21 (Xu et al ., ), AtBBX22 (Chang et al ., ) and AtBBX23 (Zhang et al ., ) are positive regulators of anthocyanin biosynthesis, while AtBBX24 (Job et al ., ), AtBBX25 (Gangappa et al ., ) and AtBBX32 (Holtan et al ., ) suppress anthocyanin accumulation. In most cases, BBXs directly transcriptionally regulate the anthocyanin biosynthesis‐related genes or indirectly regulate these genes through interactions with other proteins, such as HY5 (Gangappa and Botto, ).…”

Section: Introductionmentioning

confidence: 99%

BBX16, a B‐box protein, positively regulates light‐induced anthocyanin accumulation by activating MYB10 in red pear

Bai

Tao

Tang

et al. 2019

Plant Biotechnology Journal

201

151

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Summary The red coloration of pear (Pyrus pyrifolia) results from anthocyanin accumulation in the fruit peel. Light is required for anthocyanin biosynthesis in pear. A pear homolog of Arabidopsis thaliana BBX22, PpBBX16, was differentially expressed after fruits were removed from bags and may be involved in anthocyanin biosynthesis. Here, the expression and function of PpBBX16 were analysed. PpBBX16's expression was highly induced by white‐light irradiation, as was anthocyanin accumulation. PpBBX16's ectopic expression in Arabidopsis increased anthocyanin biosynthesis in the hypocotyls and tops of flower stalks. PpBBX16 was localized in the nucleus and showed trans‐activity in yeast cells. Although PpBBX16 could not directly bind to the promoter of PpMYB10 or PpCHS in yeast one‐hybrid assays, the complex of PpBBX16/PpHY5 strongly trans‐activated anthocyanin pathway genes in tobacco. PpBBX16's overexpression in pear calli enhanced the red coloration during light treatments. Additionally, PpBBX16's transient overexpression in pear peel increased anthocyanin accumulation, while virus‐induced gene silencing of PpBBX16 decreased anthocyanin accumulation. The expression patterns of pear BBX family members were analysed, and six additional BBX genes, which were differentially expressed during light‐induced anthocyanin biosynthesis, were identified. Thus, PpBBX16 is a positive regulator of light‐induced anthocyanin accumulation, but it could not directly induce the expression of the anthocyanin biosynthesis‐related genes by itself but needed PpHY5 to gain full function. Our work uncovered regulatory modes for PpBBX16 and suggested the potential functions of other pear BBX genes in the regulation of anthocyanin accumulation, thereby providing target genes for further studies on anthocyanin biosynthesis.

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“…In the C-terminal region, the VP pair is critical for the interaction of the BBX proteins with COP1, which regulates the dark-specific degradation of proteins [30]. Recent studies confirmed the role of the C-terminal region of BBX proteins in photomorphogenesis by swapping between the domains of AtBBX21 and AtBBX24, positive and negative regulators of this process, respectively [31]. Transgenic Arabidopsis plants producing AtBBX21 with the C-terminal region of AtBBX24 had reduced anthocyanin contents and longer hypocotyls at high intensities of light, while transgenic plants producing AtBBX24 with the C-terminal of AtBBX21 showed an enhanced accumulation of anthocyanin and shorter hypocotyls, resembling the phenotype of plants ectopically expressing AtBBX21 in Arabidopsis .…”

Section: Discussionmentioning

confidence: 99%

“…The C-terminal regions of BBX proteins have recently been reported to play important roles in photomorphogenesis [31]. Future research on the roles of the C-terminal region of the rice BBX proteins may provide a more clear insight into the regulatory mechanism of anthocyanin accumulation in rice seeds.…”

Section: Discussionmentioning

confidence: 99%

A Rice B-Box Protein, OsBBX14, Finely Regulates Anthocyanin Biosynthesis in Rice

Kim

Park

Lee

et al. 2018

IJMS

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Anthocyanins are responsible pigments for giving attractive colors of plant organs and nutraceutical benefits of grains. Anthocyanin biosynthesis is known to be regulated by transcription factors and other regulatory proteins. In rice (Oryza sativa), the R2R3 MYB transcription factor (TF) OsC1 and a bHLH TF, OsB2, were previously reported to control anthocyanin biosynthesis in vegetative tissues and seeds, respectively; however, the regulatory mechanisms of the anthocyanin biosynthesis by TFs remain largely unknown. In this study, we identified OsBBX14, a homolog of Arabidopsis thaliana B-box domain protein 22 (AtBBX22), and investigated its function. The transcript level of OsBBX14 was high in pigmented rice seeds and gradually increased as the seeds matured. The ectopic expression of OsBBX14 in Arabidopsis resulted in a dramatic increase in anthocyanin accumulation in its seedlings. Using a steroid receptor-based inducible activation system, OsBBX14 and OsHY5 were found to directly activate OsC1 or OsB2 in an independent or collaborative manner. Yeast two hybrid revealed that the second B-box domain of OsBBX14 physically interacts with the bZIP domain of OsHY5. These results suggest that the anthocyanin biosynthesis in rice is induced and finely tuned by OsBBX14 in collaboration with OsHY5.

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Two B-Box Proteins Regulate Photomorphogenesis by Oppositely Modulating HY5 through their Diverse C-Terminal Domains

Cited by 110 publications

References 56 publications

Opposite roles of group IV BBX proteins: Exploring missing links between structural and functional diversity

Opposite roles of group IV BBX proteins: Exploring missing links between structural and functional diversity

BBX16, a B‐box protein, positively regulates light‐induced anthocyanin accumulation by activating MYB10 in red pear

A Rice B-Box Protein, OsBBX14, Finely Regulates Anthocyanin Biosynthesis in Rice

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