TRANSPARENT TESTA GLABRA 1 participates in flowering time regulation in Arabidopsis thaliana

Pleiotropic regulatory factors mediate concerted responses of the plant’s trait network to endogenous and exogenous cues. TRANSPARENT TESTA GLABRA 1 (TTG1) is a pleiotropic regulator that has been predominantly described in its role as a regulator of early accessible developmental traits. Although its closest homologs LIGHT-REGULATED WD1 (LWD1) and LWD2 are regulators of photoperiodic flowering, a role of TTG1 in flowering time regulation has not been reported. Here we reveal that TTG1 is a regulator of flowering time in Arabidopsis thaliana and changes transcription levels of different targets within the flowering time regulatory pathway. TTG1 mutants flower early and TTG1 overexpression lines flower late at long-day conditions. Consistently, TTG1 can suppress the transcript levels of the floral integrators FLOWERING LOCUS T and SUPPRESSOR OF OVEREXPRESSION OF CO1 and can act as an activator of circadian clock components. Moreover, TTG1 might form feedback loops at the protein level. The TTG1 protein interacts with PSEUDO RESPONSE REGULATOR (PRR)s and basic HELIX-LOOP-HELIX 92 (bHLH92) in yeast. In planta, the respective pairs exhibit interesting patterns of localization including a recruitment of TTG1 by PRR5 to subnuclear foci. This mechanism proposes additional layers of regulation by TTG1 and might aid to specify the function of bHLH92. Within another branch of the pathway, TTG1 can elevate FLOWERING LOCUS C (FLC) transcript levels. FLC mediates signals from the vernalization, ambient temperature and autonomous pathway and the circadian clock is pivotal for the plant to synchronize with diurnal cycles of environmental stimuli like light and temperature. Our results suggest an unexpected positioning of TTG1 upstream of FLC and upstream of the circadian clock. In this light, this points to an adaptive value of the role of TTG1 in respect to flowering time regulation.

Download Full-text

Initial embedding of TRANSPARENT TESTA GLABRA 1 in the Arabidopsis thaliana flowering time regulatory pathway

10.7287/peerj.preprints.27974 ◽

2019 ◽

Author(s):

Barbara A M Paffendorf ◽

Rawan Qassrawi ◽

Andrea M Meys ◽

Laura Trimborn ◽

Andrea Schrader

Keyword(s):

Arabidopsis Thaliana ◽

Circadian Clock ◽

Flowering Time ◽

Response Regulator ◽

Regulatory Pathway ◽

In Planta ◽

Transcript Levels ◽

Transparent Testa ◽

Flowering Locus

Pleiotropic regulatory factors mediate concerted responses of the plant’s trait network to endogenous and exogenous cues. TRANSPARENT TESTA GLABRA 1 (TTG1) is a pleiotropic regulator that has been predominantly described in its role as a regulator of early accessible developmental traits. Although its closest homologs LIGHT-REGULATED WD1 (LWD1) and LWD2 are regulators of photoperiodic flowering, a role of TTG1 in flowering time regulation has not been reported. Here we reveal that TTG1 is a regulator of flowering time in Arabidopsis thaliana and changes transcription levels of different targets within the flowering time regulatory pathway. TTG1 mutants flower early and TTG1 overexpression lines flower late at long-day conditions. Consistently, TTG1 can suppress the transcript levels of the floral integrators FLOWERING LOCUS T and SUPPRESSOR OF OVEREXPRESSION OF CO1 and can act as an activator of circadian clock components. Moreover, TTG1 might form feedback loops at the protein level. The TTG1 protein interacts with PSEUDO RESPONSE REGULATOR (PRR)s and basic HELIX-LOOP-HELIX 92 (bHLH92) in yeast. In planta, the respective pairs exhibit interesting patterns of localization including a recruitment of TTG1 by PRR5 to subnuclear foci. This mechanism proposes additional layers of regulation by TTG1 and might aid to specify the function of bHLH92. Within another branch of the pathway, TTG1 can elevate FLOWERING LOCUS C (FLC) transcript levels. FLC mediates signals from the vernalization, ambient temperature and autonomous pathway and the circadian clock is pivotal for the plant to synchronize with diurnal cycles of environmental stimuli like light and temperature. Our results suggest an unexpected positioning of TTG1 upstream of FLC and upstream of the circadian clock. In this light, this points to an adaptive value of the role of TTG1 in respect to flowering time regulation.

Download Full-text

The Role of FLOWERING LOCUS C Relatives in Cereals

Frontiers in Plant Science ◽

10.3389/fpls.2020.617340 ◽

2020 ◽

Vol 11 ◽

Author(s):

Alice Kennedy ◽

Koen Geuten

Keyword(s):

Arabidopsis Thaliana ◽

Flowering Time ◽

Developmental Process ◽

Cereal Crops ◽

Time Behavior ◽

Dominant Effect ◽

Flowering Locus C ◽

Flowering Locus ◽

Fine Tune

FLOWERING LOCUS C (FLC) is one of the best characterized genes in plant research and is integral to vernalization-dependent flowering time regulation. Yet, despite the abundance of information on this gene and its relatives in Arabidopsis thaliana, the role FLC genes play in other species, in particular cereal crops and temperate grasses, remains elusive. This has been due in part to the comparative reduced availability of bioinformatic and mutant resources in cereals but also on the dominant effect in cereals of the VERNALIZATION (VRN) genes on the developmental process most associated with FLC in Arabidopsis. The strong effect of the VRN genes has led researchers to believe that the entire process of vernalization must have evolved separately in Arabidopsis and cereals. Yet, since the confirmation of the existence of FLC-like genes in monocots, new light has been shed on the roles these genes play in both vernalization and other mechanisms to fine tune development in response to specific environmental conditions. Comparisons of FLC gene function and their genetic and epigenetic regulation can now be made between Arabidopsis and cereals and how they overlap and diversify is coming into focus. With the advancement of genome editing techniques, further study on these genes is becoming increasingly easier, enabling us to investigate just how essential FLC-like genes are to modulating flowering time behavior in cereals.

Download Full-text

Faculty Opinions recommendation of Role of FRIGIDA and FLOWERING LOCUS C in determining variation in flowering time of Arabidopsis.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1026594.325278 ◽

2005 ◽

Author(s):

Michael Lenhard

Keyword(s):

Flowering Time ◽

Flowering Locus C ◽

Flowering Locus

Download Full-text

BBX32 Interacts with AGL24 Involved in Flowering Time Control in Chinese Cabbage (Brassica rapa L. ssp. pekinensis)

Notulae Botanicae Horti Agrobotanici Cluj-Napoca ◽

10.15835/nbha47111205 ◽

2018 ◽

Vol 47 (1) ◽

pp. 34-45

Author(s):

Guan-Peng MA ◽

Da-Qin ZHAO ◽

Tian-Wen WANG ◽

Lin-Bi ZHOU ◽

Gui-Lian LI

Keyword(s):

Arabidopsis Thaliana ◽

Circadian Clock ◽

Flowering Time ◽

Brassica Rapa ◽

Chinese Cabbage ◽

Protein Interactions ◽

Protein Protein Interactions ◽

Time Control ◽

Flowering Time Control ◽

Molecular Regulatory Mechanisms

B-box (BBX) zinc finger proteins play critical roles in both vegetative and reproductive development in plants. Many BBX proteins have been identified in Arabidopsis thaliana as floral transition regulatory factors, such as CO, BBX7 (COL9), BBX19, and BBX32. BBX32 is involved in flowering time control through repression of COL3 in Arabidopsis thaliana, but it is still elusive that whether and how BBX32 directly interacts with flowering signal integrators of AGAMOUS-LIKE 24 (AGL24) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) in Chinese cabbage (Brassica rapa L. ssp. pekinensis) or other plants. In this study, B-box-32(BBX32), a transcription factor in this family with one B-box motif was cloned from B. rapa, acted as a circadian clock protein, showing expression changes during the circadian period. Additional experiments using GST pull-down and yeast two-hybrid assays indicated that BrBBX32 interacts with BrAGL24 and does not interact with BrSOC1, while BrAGL24 does interact with BrSOC1. To investigate the domains involved in these protein-protein interactions, we tested three regions of BrBBX32. Only the N-terminus interacted with BrAGL24, indicating that the B-box domain may be the key region for protein interaction. Based on these data, we propose that BrBBX32 may act in the circadian clock pathway and relate to the mechanism of flowering time regulation by binding to BrAGL24 through the B-box domain. This study will provide valuable information for unraveling the molecular regulatory mechanisms of BrBBX32 in flowering time of B. rapa.

Download Full-text

Dehydroabietinal promotes flowering time and plant defense in Arabidopsis via the autonomous pathway genes FLOWERING LOCUS D, FVE, and RELATIVE OF EARLY FLOWERING 6

Journal of Experimental Botany ◽

10.1093/jxb/eraa232 ◽

2020 ◽

Vol 71 (16) ◽

pp. 4903-4913 ◽

Cited By ~ 1

Author(s):

Zulkarnain Chowdhury ◽

Devasantosh Mohanty ◽

Mrunmay K Giri ◽

Barney J Venables ◽

Ratnesh Chaturvedi ◽

...

Keyword(s):

Flowering Time ◽

Systemic Acquired Resistance ◽

Defense Mechanism ◽

Acquired Resistance ◽

Early Flowering ◽

Negative Regulator ◽

Flowering Locus T ◽

Autonomous Pathway ◽

Abietane Diterpenoids ◽

Flowering Locus

Abstract Abietane diterpenoids are tricyclic diterpenes whose biological functions in angiosperms are largely unknown. Here, we show that dehydroabietinal (DA) fosters transition from the vegetative phase to reproductive development in Arabidopsis thaliana by promoting flowering time. DA’s promotion of flowering time was mediated through up-regulation of the autonomous pathway genes FLOWERING LOCUS D (FLD), RELATIVE OF EARLY FLOWERING 6 (REF6), and FVE, which repress expression of FLOWERING LOCUS C (FLC), a negative regulator of the key floral integrator FLOWERING LOCUS T (FT). Our results further indicate that FLD, REF6, and FVE are also required for systemic acquired resistance (SAR), an inducible defense mechanism that is also activated by DA. However, unlike flowering time, FT was not required for DA-induced SAR. Conversely, salicylic acid, which is essential for the manifestation of SAR, was not required for the DA-promoted flowering time. Thus, although the autonomous pathway genes FLD, REF6, and FVE are involved in SAR and flowering time, these biological processes are not interdependent. We suggest that SAR and flowering time signaling pathways bifurcate at a step downstream of FLD, REF6, and FVE, with an FLC-dependent arm controlling flowering time, and an FLC-independent pathway controlling SAR.

Download Full-text