OsbZIP62/OsFD7, a functional ortholog of FLOWERING LOCUS D, regulates floral transition and panicle development in rice

Abstract

We have characterized a rice bZIP protein coding gene OsbZIP62/OsFD7 that expresses preferentially in SAM and during early panicle developmental stages in comparison to other OsFDs characterised to date. Surprisingly, unlike OsFD1, OsFD7 interacts directly and more efficiently with OsFTLs; the interaction is strongest with OsFTL1 followed by Hd3a and RFT1, as confirmed by FLIM-FRET analysis. Also, OsFD7 is phosphorylated at its C-terminal end by OsCDPK41 and OsCDPK49 in vitro and this phosphorylated moiety is recognized by OsGF14 proteins. OsFD7 RNAi transgenics were late flowering; the transcript levels of some floral meristem identity genes (e.g. OsMADS14, OsMADS15 and OsMADS18) were also down-regulated. RNAi lines also exhibited dense panicle morphology with increase in the number of primary and secondary branches resulting in longer panicles and more seeds probably due to downregulation of SEPALLATA (SEP) family genes. In comparison to other FD-like proteins characterized thus far from rice, it appears that OsFD7 may have undergone diversification during evolution resulting in the acquisition of newer functions and thus playing dual role in floral transition and panicle development in rice.

Integration of GWAS, linkage analysis and transcriptome analysis to reveal the genetic basis of flowering time-related traits in maize

“…For example, Zm00001d023424 encodes the bZIP transcription factor, and Zm00001d047250 encodes the PLATZ transcription factor. In rice, OsbZIP62 , which is a functional orthologue of FLOWERING LOCUS D, regulates the floral transition and panicle development ( Kaur et al., 2021 ). In grapevine, VviPLATZ1 is a major factor that controls female flower morphology determination ( Iocco-Corena et al., 2021 ).…”

Environmental control of rice flowering time

“…The structure of the FAC was first shown to contain the OsFD1 transcription factor, but it was later demonstrated that several bZIPs can replace OsFD1 ( Tsuji et al., 2013 ; Brambilla et al., 2017 ; Jang et al., 2017 ; Cerise et al., 2021 ; Kaur et al., 2021 ). bZIPs act as dimers, and the complex orients their DNA-binding domain towards the DNA.…”

“…Thus, OsCIPK3 specifically affects the assembly of an RFT1/14-3-3/OsFD1 complex under LDs, suggesting that another unknown kinase operates under SDs. The calcium-dependent protein kinases OsCDPK41 and OsCDPK49 interact with and phosphorylate OsFD7, which forms FACs with Hd3a and RFT1 as well as with FT-L1 ( Kaur et al., 2021 ). The phenotypic consequences of their mutation have not yet been determined, but they could be good candidates contributing to bZIP phosphorylation under SDs.…”

Visualization of in vivo protein–protein interactions in plants

“…Additionally, FLIM is largely independent of protein concentration. Therefore, FRET-FLIM measurements are widely considered as more reliable than the detection of FRET by APB and spectral imaging, and have been successfully applied in planta ( Stahl et al , 2013 ; Bücherl et al , 2014 ; Somssich et al , 2015 ; Long et al , 2017 ; Weidtkamp-Peters and Stahl, 2017 ; Betegón-Putze et al , 2021 ; Kaur et al , 2021 ).…”