Molecular interaction between PHO2 and GIGANTEA reveals a new crosstalk between flowering time and Pi homeostasis in rice
Ontology highlight
ABSTRACT: Using a yeast to hybrid screen, it was found that PHO2, a key regulator of phosphate homeostasis, could interact with GIGANTEA, a key regulator of flowering time. In addition, mutant analysis revealed that both the pho2 and gi mutants shared similar phenotypes, both at the phosphate and flowering time levels. We used microarrays to analyse the effects of each mutation (pho2 or gi) on global gene expression, and assessed the proportion of genes similalry regulated in both mutants, in both shoots and roots.
ORGANISM(S): Oryza sativa Oryza sativa Japonica Group
Project description:Using a yeast to hybrid screen, it was found that PHO2, a key regulator of phosphate homeostasis, could interact with GIGANTEA, a key regulator of flowering time. In addition, mutant analysis revealed that both the pho2 and gi mutants shared similar phenotypes, both at the phosphate and flowering time levels. We used microarrays to analyse the effects of each mutation (pho2 or gi) on global gene expression, and assessed the proportion of genes similalry regulated in both mutants, in both shoots and roots. Wild-type (Nipponbare), pho2 and gi knock-out rice plants were grown to 21-days before harvesting root and shoot separately.
Project description:Plants use their endogenous clock to regulate many physiological processes related to their survival and adaptability. GIGANTEA (GI), one of the clock proteins, contributes to the maintenance of circadian period length and amplitude and also regulates flowering time and hypocotyl growth in response to day length. In addition to GI, EARLY FLOWERING 4 (ELF4), another clock regulator, also contributes to these processes. However, little is known about the overall interactions between GI and ELF4 in Arabidopsis. In this study, we investigated the genetic interactions between GI and ELF4 in circadian output regulation. The results show that GI is dominant to ELF4 in flowering time determination, but ELF4 is dominant to GI in hypocotyl growth regulation. Moreover, GI and ELF4 have a synergistic effect on endogenous clock regulation. Further, gene expression profiling of gi-2, elf4, and gi-2 elf4 mutants confirmed that GI and ELF4 had differential dominant effects on circadian physiological outputs at dawn and dusk, respectively. This differential dominance of GI and ELF4 provides a potential means to achieve the diversity in the regulation of circadian physiological outputs including flowering time and hypocotyl growth.
Project description:Plants use their endogenous clock to regulate many physiological processes related to their survival and adaptability. GIGANTEA (GI), one of the clock proteins, contributes to the maintenance of circadian period length and amplitude and also regulates flowering time and hypocotyl growth in response to day length. In addition to GI, EARLY FLOWERING 4 (ELF4), another clock regulator, also contributes to these processes. However, little is known about the overall interactions between GI and ELF4 in Arabidopsis. In this study, we investigated the genetic interactions between GI and ELF4 in circadian output regulation. The results show that GI is dominant to ELF4 in flowering time determination, but ELF4 is dominant to GI in hypocotyl growth regulation. Moreover, GI and ELF4 have a synergistic effect on endogenous clock regulation. Further, gene expression profiling of gi-2, elf4, and gi-2 elf4 mutants confirmed that GI and ELF4 had differential dominant effects on circadian physiological outputs at dawn and dusk, respectively. This differential dominance of GI and ELF4 provides a potential means to achieve the diversity in the regulation of circadian physiological outputs including flowering time and hypocotyl growth. The genetic interactions between GI and ELF4 could be time-dependent functional dominance along a day, called temporal dominance hereafter. To test this hypothesis, we performed gene expression profiling of WT, gi-2, elf4 and gi elf4 plants at dawn (ZT1) and dusk (ZT16).
Project description:Plants monitor and integrate temperature, photoperiod and light quality signals to respond to continuous changes in their environment. The GIGANTEA (GI) protein is central in diverse signaling pathways, including photoperiodic, sugar and light signaling pathways, stress responses and circadian clock regulation. Previously, GI was shown to activate expression of the key floral regulators CONSTANS (CO) and FLOWERING LOCUS T (FT) by facilitating degradation of a family of CYCLING DOF FACTOR (CDF) transcriptional repressors. However, whether CDFs are implicated in other processes regulated by GI remains unclear. We investigated the contribution of the GI-CDF module to traits that depend on GI. Transcriptome profiling indicated that mutations in GI and the CDFs have antagonistic effects on expression of a wider set of genes than CO and FT, whilst other genes are regulated by GI independently of the CDFs. Detailed expression studies followed by phenotypic assays showed that the CDFs function downstream of GI to control responses to freezing temperatures and growth, but are not necessary for proper clock function. Thus GI-mediated regulation of CDFs contributes to several processes in addition to flowering, but is not implicated in all of the phenotypes influenced by GI.
Project description:GIGANTEA (GI) is a plant-specific, circadian clock-regulated, nuclear protein with pleiotropic functions studied in many plant species. It is involved in flowering, circadian clock control, chloroplast biogenesis, carbohydrate metabolism, stress responses and synthesis of volatiles. In potato (Solanum tuberosum L.), however, only its role in tuber initiation is reported. Based on the findings in other plant species we hypothesized that the function of GI is not restricted to tuberization in potato. To test this hypothesis we repressed the expression of a GI gene, StGI.04 in the commercial potato cultivar ‘Désirée’ and investigated the effect of repression at morphological and transcriptome level. We found that, like GI in other plant species, StGI.04 influences the expression of the key genes of circadian clock, flowering, starch synthesis and stress responses. Furthermore, we detected a novel function of a GI gene in influencing the anthocyanin synthesis and skin colour of potato tubers.
Project description:Plants monitor and integrate temperature, photoperiod and light quality signals to respond to continuous changes in their environment. The GIGANTEA (GI) protein is central in diverse signaling pathways, including photoperiodic, sugar and light signaling pathways, stress responses and circadian clock regulation. Previously, GI was shown to activate expression of the key floral regulators CONSTANS (CO) and FLOWERING LOCUS T (FT) by facilitating degradation of a family of CYCLING DOF FACTOR (CDF) transcriptional repressors. However, whether CDFs are implicated in other processes regulated by GI remains unclear. We investigated the contribution of the GI-CDF module to traits that depend on GI. Transcriptome profiling indicated that mutations in GI and the CDFs have antagonistic effects on expression of a wider set of genes than CO and FT, whilst other genes are regulated by GI independently of the CDFs. Detailed expression studies followed by phenotypic assays showed that the CDFs function downstream of GI to control responses to freezing temperatures and growth, but are not necessary for proper clock function. Thus GI-mediated regulation of CDFs contributes to several processes in addition to flowering, but is not implicated in all of the phenotypes influenced by GI. Seedlings of Col-0, the cdf1-R cdf2-1 cdf3-1 cdf5-1 quadruple mutant, gi-100 and gi-100 cdf1-R cdf2-1 cdf3-1 cdf5-1 quintuple mutant were grown for 10 days under LD conditions (16h light/8h dark). The aerial part of the seedlings was collected at ZT12 and RNA was prepared from three biological replicas
Project description:Interaction proteomics time course over 24h every 4h, looking for novel interactors of the circadian clock and flowering time protein GIGANTEA. Plants expressing 35S:GIGANTEA:3xFlag6His were used, as well as WT plants for a background control.
Project description:In S. cerevisiae, the phosphate starvation (PHO) responsive transcription factors Pho4 and Pho2 are jointly required for induction of phosphate response genes and survival in phosphate starvation conditions. In the related human commensal and pathogen C. glabrata, Pho4 is required but Pho2 is dispensable for survival in phosphate-limited conditions and is only partially required for inducing the phosphate response genes. This reduced dependence on Pho2 evolved in C. glabrata and closely related species. Pho4 orthologs that are less dependent on Pho2 induce more genes when introduced into the S. cerevisiae background, and Pho4 in C. glabrata both binds to more sites and induces more genes with expanded functional roles compared to Pho4 in S. cerevisiae. We used RNA-seq to profile the transcriptome of wild type and mutants of Pho4 / Pho2 in C. glabrata, to identify genes induced by Pho4.
Project description:In S. cerevisiae, the phosphate starvation (PHO) responsive transcription factors Pho4 and Pho2 are jointly required for induction of phosphate response genes and survival in phosphate starvation conditions. In the related human commensal and pathogen C. glabrata, Pho4 is required but Pho2 is dispensable for survival in phosphate-limited conditions and is only partially required for inducing the phosphate response genes. This reduced dependence on Pho2 evolved in C. glabrata and closely related species. Pho4 orthologs that are less dependent on Pho2 induce more genes when introduced into the S. cerevisiae background, and Pho4 in C. glabrata both binds to more sites and induces more genes with expanded functional roles compared to Pho4 in S. cerevisiae. We used RNA-seq to profile the transcriptome of wild type and mutants of Pho4 / Pho2, or Pho4 ortholog swap in S. cerevisiae, to identify genes induced by Pho4 or its orthologs in S. cerevisiae background.
Project description:The Arabidopsis thaliana glycosyl transferases SPINDLY (SPY) and SECRET AGENT (SEC) modify nuclear and cytosolic proteins with O-linked fucose or O-linked Nacetylglucosamine (O-GlcNAc), respectively. O-fucose and O-GlcNAc modifications can occur at the same sites. SPY interacts physically and genetically with GIGANTEA (GI), suggesting that it could be modified by both enzymes. Previously, we found that, when co-expressed in Escherichia coli, SEC modifies GI; however, the modification site was not determined. By analyzing the overlapping sub-fragments of GI, we identified a region that was modified by SEC in E. coli. Modification was undetectable when threonine 829 (T829) was mutated to alanine, while the T834A and T837A mutations reduced the modification, suggesting that T829 was the primary or the only modification site. Mapping using mass spectrometry detected only the modification of T829. Previous studies have shown that the positions modified by SEC in E. coli are modified in planta, suggesting that T829 is O-GlcNAc modified in planta.