FKF1 F‐box protein promotes flowering in part by negatively regulating DELLA protein stability under long‐day photoperiod in
            Arabidopsis

The phytohormone gibberellin and the DELLA proteins act together to control key aspects of plant development. Gibberellin induces degradation of DELLA proteins by recruitment of an F-box protein using a molecular switch: a gibberellin-bound nuclear receptor interacts with the N-terminal domain of DELLA proteins, and this event primes the DELLA C-terminal domain for interaction with the F-box protein. However, the mechanism of signalling between the N- and C-terminal domains of DELLA proteins is unresolved. In the present study, we used in vivo and in vitro approaches to characterize di- and tri-partite interactions of the DELLA protein RGL1 (REPRESSOR OF GA1-3-LIKE 1) of Arabidopsis thaliana with the gibberellin receptor GID1A (GIBBERELLIC ACID-INSENSITIVE DWARF-1A) and the F-box protein SLY1 (SLEEPY1). Deuterium-exchange MS unequivocally showed that the entire N-terminal domain of RGL1 is disordered prior to interaction with the GID1A; furthermore, association/dissociation kinetics, determined by surface plasmon resonance, predicts a two-state conformational change of the RGL1 N-terminal domain upon interaction with GID1A. Additionally, competition assays with monoclonal antibodies revealed that contacts mediated by the short helix Asp-Glu-Leu-Leu of the hallmark DELLA motif are not essential for the GID1A–RGL1 N-terminal domain interaction. Finally, yeast two- and three-hybrid experiments determined that unabated communication between N- and C-terminal domains of RGL1 is required for recruitment of the F-box protein SLY1.

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Morphological, Physiological, and Molecular Responses of Sweetly Fragrant Luculia gratissima During the Floral Transition Stage Induced by Short-Day Photoperiod

Frontiers in Plant Science ◽

10.3389/fpls.2021.715683 ◽

2021 ◽

Vol 12 ◽

Author(s):

Xiongfang Liu ◽

Youming Wan ◽

Jing An ◽

Xiujiao Zhang ◽

Yurong Cao ◽

...

Keyword(s):

Developmental Stages ◽

Response Regulator ◽

Genetic Regulation ◽

Floral Transition ◽

Flowering Plant ◽

Flower Bud ◽

Woody Perennial ◽

Short Day ◽

Long Day ◽

F Box Protein

Photoperiod-regulated floral transition is vital to the flowering plant. Luculia gratissima “Xiangfei” is a flowering ornamental plant with high development potential economically and is a short-day woody perennial. However, the genetic regulation of short-day-induced floral transition in L. gratissima is unclear. To systematically research the responses of L. gratissima during this process, dynamic changes in morphology, physiology, and transcript levels were observed and identified in different developmental stages of long-day- and short-day-treated L. gratissima plants. We found that floral transition in L. gratissima occurred 10 d after short-day induction, but flower bud differentiation did not occur at any stage under long-day conditions. A total of 1,226 differentially expressed genes were identified, of which 146 genes were associated with flowering pathways of sugar, phytohormones, photoperiod, ambient temperature, and aging signals, as well as floral integrator and meristem identity genes. The trehalose-6-phosphate signal positively modulated floral transition by interacting with SQUAMOSA PROMOTER-BINDING-LIKE PROTEIN 4 (SPL4) in the aging pathway. Endogenous gibberellin, abscisic acid, cytokinin, and jasmonic acid promoted floral transition, whereas strigolactone inhibited it. In the photoperiod pathway, FD, CONSTANS-LIKE 12, and nuclear factors Y positively controlled floral transition, whereas PSEUDO-RESPONSE REGULATOR 7, FLAVIN-BINDING KELCH REPEAT F-BOX PROTEIN 1, and LUX negatively regulated it. SPL4 and pEARLI1 positively affected floral transition. Suppressor of Overexpression of Constans 1 and AGAMOUSLIKE24 integrated multiple flowering signals to modulate the expression of FRUITFULL/AGL8, AP1, LEAFY, SEPALLATAs, SHORT VEGETATIVE PHASE, and TERMINAL FLOWER 1, thereby regulating floral transition. Finally, we propose a regulatory network model for short-day-induced floral transition in L. gratissima. This study improves our understanding of flowering time regulation in L. gratissima and provides knowledge for its production and commercialization.

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The ubiquitin–proteasome system and skeletal muscle wasting

Essays in Biochemistry ◽

10.1042/bse0410173 ◽

2005 ◽

Vol 41 ◽

pp. 173-186 ◽

Cited By ~ 110

Author(s):

Didier Attaix ◽

Sophie Ventadour ◽

Audrey Codran ◽

Daniel Béchet ◽

Daniel Taillandier ◽

...

Keyword(s):

Skeletal Muscle ◽

Muscle Wasting ◽

Proteolytic Enzymes ◽

Cathepsin L ◽

Ubiquitin Proteasome System ◽

Complete Breakdown ◽

Skeletal Muscle Proteins ◽

Ubiquitin Proteasome ◽

Tripeptidyl Peptidase Ii ◽

F Box Protein

The ubiquitin–proteasome system (UPS) is believed to degrade the major contractile skeletal muscle proteins and plays a major role in muscle wasting. Different and multiple events in the ubiquitination, deubiquitination and proteolytic machineries are responsible for the activation of the system and subsequent muscle wasting. However, other proteolytic enzymes act upstream (possibly m-calpain, cathepsin L, and/or caspase 3) and downstream (tripeptidyl-peptidase II and aminopeptidases) of the UPS, for the complete breakdown of the myofibrillar proteins into free amino acids. Recent studies have identified a few critical proteins that seem necessary for muscle wasting {i.e. the MAFbx (muscle atrophy F-box protein, also called atrogin-1) and MuRF-1 [muscle-specific RING (really interesting new gene) finger 1] ubiquitin–protein ligases}. The characterization of their signalling pathways is leading to new pharmacological approaches that can be useful to block or partially prevent muscle wasting in human patients.

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