Plants coordinate their growth and development with the environment through integration of circadian clock and photosensory pathways. In Arabidopsis thaliana, rhythmic hypocotyl elongation in short days (SD) is enhanced at dawn by the basic-helix-loop-helix (bHLH) transcription factors PHYTOCHROME-INTERACTING FACTORS (PIFs) directly inducing expression of growth-related genes [1-6]. PIFs accumulate progressively during the night and are targeted for degradation by active phytochromes in the light, when growth is reduced. Although PIF proteins are also detected during the day hours [7-10], their growth-promoting activity is inhibited through unknown mechanisms. Recently, the core clock components and transcriptional repressors PSEUDO-RESPONSE REGULATORS PRR9/7/5 [11, 12], negative regulators of hypocotyl elongation [13, 14], were described to associate to G boxes [15], the DNA motifs recognized by the PIFs [16, 17], suggesting that PRR and PIF function might converge antagonistically to regulate growth. Here we report that PRR9/7/5 and PIFs physically interact and bind to the same promoter region of pre-dawn-phased, growth-related genes, and we identify the transcription factor CDF5 [18, 19] as target of this interplay. In SD, CDF5 expression is sequentially repressed from morning to dusk by PRRs and induced pre-dawn by PIFs. Consequently, CDF5 accumulates specifically at dawn, when it induces cell elongation. Our findings provide a framework for recent TIMING OF CAB EXPRESSION 1 (TOC1/PRR1) data [5, 20] and reveal that the long described circadian morning-to-midnight waves of the PRR transcriptional repressors (PRR9, PRR7, PRR5, and TOC1) [21] jointly gate PIF activity to dawn to prevent overgrowth through sequential regulation of common PIF-PRR target genes such as CDF5.

Circadian rhythms of gene expression are generated by the combinatorial action of transcriptional and translational feedback loops as well as chromatin remodelling events. Recently, long noncoding RNAs (lncRNAs) that are natural antisense transcripts (NATs) to transcripts encoding central oscillator components were proposed as modulators of core clock function in mammals (Per) and fungi (frq/qrf). Although oscillating lncRNAs exist in plants, their functional characterization is at an initial stage. By screening an Arabidopsis thaliana lncRNA custom-made array we identified CDF5 LONG NONCODING RNA (FLORE), a circadian-regulated lncRNA that is a NAT of CDF5. Quantitative real-time RT-PCR confirmed the circadian regulation of FLORE, whereas GUS-staining and flowering time evaluation were used to determine its biological function. FLORE and CDF5 antiphasic expression reflects mutual inhibition in a similar way to frq/qrf. Moreover, whereas the CDF5 protein delays flowering by directly repressing FT transcription, FLORE promotes it by repressing several CDFs (CDF1, CDF3, CDF5) and increasing FT transcript levels, indicating both cis and trans function. We propose that the CDF5/FLORE NAT pair constitutes an additional circadian regulatory module with conserved (mutual inhibition) and unique (function in trans) features, able to fine-tune its own circadian oscillation, and consequently, adjust the onset of flowering to favourable environmental conditions.

Hypocotyl elongation relies on directional cell expansion, a process under light and circadian clock control. Under short photoperiods (SD), hypocotyl elongation in Arabidopsis thaliana follows a rhythmic pattern, a process in which circadian morning-to-midnight waves of the transcriptional repressors PSEUDO-RESPONSE REGULATORS (PRRs) jointly gate PHYTOCHROME-INTERACTING FACTOR (PIF) activity to dawn. Previously, we described CYCLING DOF FACTOR 5 (CDF5) as a target of this antagonistic PRR/PIF dynamic interplay. Under SD, PIFs induce CDF5 accumulation specifically at dawn, when it promotes the expression of positive cell elongation regulators such as YUCCA8 to induce growth. In contrast to SD, hypocotyl elongation under long days (LD) is largely reduced. Here, we examine whether CDF5 is an actor in this photoperiod specific regulation. We report that transcription of CDF5 is robustly induced in SD compared to LD, in accordance with PIFs accumulating to higher levels in SD, and in contrast to other members of the CDF family, whose expression is mainly clock regulated and have similar waveforms in SD and LD. Notably, when CDF5 was constitutively expressed under LD, CDF5 protein accumulated to levels comparable to SD but was inactive in promoting cell elongation. Similar results were observed for CDF1. Our findings indicate that both CDFs can promote cell elongation specifically in shorter photoperiods, however their activity in LD is inhibited at the post-translational level. These data not only expand our understanding of the biological role of CDF transcription 2 factors, but also identify a previously unrecognized regulatory layer in the photoperiodic response of hypocotyl elongation.

Plants post-embryonic organogenesis requires matching the available metabolic resources to the developmental programs. The root system is determined by the formation of lateral roots (LR), which in Arabidopsis thaliana entails the auxin-induced activation of founder cells located in the pericycle. While the allocation of sugars to roots influences root branching, how sugar availability is sensed for auxin-triggered formation of LRs remains unknown.Here, we combine metabolic profiling with cell-specific genetic interference to show that LR formation is an important sink for carbohydrate accompanied by a switch to glycolysis. We show that the target-of-rapamycin (TOR) kinase is locally activated in the pericycle and the founder cells and that both chemical and genetic inhibition of TOR kinase lead to a block of LR initiation. TOR marginally affects the auxin-induced transcriptional response of the pericycle but modulates the translation of ARF19, ARF7 and LBD16, three key targets of auxin signalling. These data place TOR as a gatekeeper for post-embryonic LR formation that integrates local auxin-dependent pathways with systemic metabolic signals, modulating the translation of auxin induced gene expression.

Primary bone lymphomas (PBL) account for approximately 3% of all malignant tumors and are commonly found in the femur or pelvis. Only 1.7% of the PBLs are found in the spine. We report the case of a 73-year-old male complaining of cervical pain with progressive loss of strength and frequent falls. The MRI showed invasion of the fourth cervical vertebra and an infiltrating prevertebral mass. A C4 corpectomy was performed. The pathology exam revealed a diffuse large B-cell lymphoma. Due to the previous condition of the patient only radiotherapy treatment was applied. PBL arising from the cervical spine is an exceptional event. The low incidence of this condition and its unspecific radiological features make the diagnosis challenging for the clinician. When neurological deficit appears, early surgery for decompression is indicated, followed by local radiotherapy and systemic chemotherapy. KEywoRds: Non Hodgkin lymphoma, Cervical vertebrae, Diffuse large B-cell lymphoma ÖZPrimer kemik lenfomaları (PKL) tüm malign tümörlerin yaklaşık %3'ünü oluşturur ve sıklıkla femur veya pelviste bulunur. PKL'lerin sadece %1,7'si omurgada bulunur. Servikal ağrı, giderek azalan güç ve sık düşmelerden yakınan 73 yaşında bir erkek olguyu sunuyoruz. MRG dördüncü servikal vertebra invazyonu ve bir infiltratif prevertebral kitle gösterdi. C4 korpektomi yapıldı. Patoloji incelemesi difüz büyük B hücreli lenfoma olarak rapor edildi. Hastanın önceki durumu nedeniyle sadece radyoterapi tedavisi uygulandı. Servikal omurgadan köken alan PKL çok nadirdir. Bu hastalığın insidansının düşüklüğü ve spesifik olmayan radyolojik özellikleri tanıyı klinisyen için zor hale getirir. Nörolojik defisit belirdiğinde, dekompresyon için erken cerrahi endikedir ve sonrasında lokal radyoterapi ve sistemik kemoterapi uygulanır.ANAHTAR sÖZCÜKLER: Non Hodgkin lenfoma, Servikal vertebra, Diffüz büyük B hücreli lenfoma