Circadian clock components in Arabidopsis III. LHY/CCA1/GI in regulating the floral integrator genes LFY/SOC1/FT to control flowering time and shoot architecture

Abstract Compared with root development regulated by external nutrients, less is known about how internal nutrients are monitored to control plasticity of shoot development. In this study, we characterize an Arabidopsis thaliana transceptor, NRT1.13 (NPF4.4), of the NRT1/PTR/NPF family. Different from most NRT1 transporters, NRT1.13 does not have the conserved proline residue between transmembrane domains 10 and 11; an essential residue for nitrate transport activity in CHL1/NRT1.1/NPF6.3. As expected, when expressed in oocytes, NRT1.13 showed no nitrate transport activity. However, when Ser 487 at the corresponding position was converted back to proline, NRT1.13 S487P regained nitrate uptake activity, suggesting that wild-type NRT1.13 cannot transport nitrate but can bind it. Subcellular localization and β-glucuronidase reporter analyses indicated that NRT1.13 is a plasma membrane protein expressed at the parenchyma cells next to xylem in the petioles and the stem nodes. When plants were grown with a normal concentration of nitrate, nrt1.13 showed no severe growth phenotype. However, when grown under low-nitrate conditions, nrt1.13 showed delayed flowering, increased node number, retarded branch outgrowth, and reduced lateral nitrate allocation to nodes. Our results suggest that NRT1.13 is required for low-nitrate acclimation and that internal nitrate is monitored near the xylem by NRT1.13 to regulate shoot architecture and flowering time.

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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.

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VASCULAR PLANT ONE-ZINC FINGER1andVOZ2repress theFLOWERING LOCUS Cclade members to control flowering time in Arabidopsis

Bioscience Biotechnology and Biochemistry ◽

10.1080/09168451.2014.932670 ◽

2014 ◽

Vol 78 (11) ◽

pp. 1850-1855 ◽

Cited By ~ 9

Author(s):

Yukiko Yasui ◽

Takayuki Kohchi

Keyword(s):

Flowering Time ◽

Vascular Plant ◽

Control Flowering Time

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ZEITLUPE and FKF1: novel connections between flowering time and circadian clock control

Trends in Plant Science ◽

10.1016/s1360-1385(00)01747-7 ◽

2000 ◽

Vol 5 (10) ◽

pp. 409-411 ◽

Cited By ~ 17

Author(s):

Tsuyoshi Mizoguchi ◽

George Coupland

Keyword(s):

Circadian Clock ◽

Flowering Time

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The F-Box Protein ZEITLUPE Confers Dosage-Dependent Control on the Circadian Clock, Photomorphogenesis, and Flowering Time

The Plant Cell ◽

10.1105/tpc.016808 ◽

2004 ◽

Vol 16 (3) ◽

pp. 769-782 ◽

Cited By ~ 136

Author(s):

David E. Somers ◽

Woe-Yeon Kim ◽

Ruishuang Geng

Keyword(s):

Circadian Clock ◽

Flowering Time ◽

F Box Protein

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

10.7287/peerj.preprints.27974v1 ◽

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.

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