The HY5-PIF regulatory module coordinates light and temperature control of photosynthetic gene transcription

The ability to interpret daily and seasonal alterations in light and temperature signals is essential for plant survival. This is particularly important during seedling establishment when the phytochrome photoreceptors activate photosynthetic pigment production for photoautotrophic growth. Phytochromes accomplish this partly through the suppression of phytochrome interacting factors (PIFs), negative regulators of chlorophyll and carotenoid biosynthesis. While the bZIP transcription factor long hypocotyl 5 (HY5), a potent PIF antagonist, promotes photosynthetic pigment accumulation in response to light. Here we demonstrate that by directly targeting a common promoter cis-element (G-box), HY5 and PIFs form a dynamic activation-suppression transcriptional module responsive to light and temperature cues. This antagonistic regulatory module provides a simple, direct mechanism through which environmental change can redirect transcriptional control of genes required for photosynthesis and photoprotection. In the regulation of photopigment biosynthesis genes, HY5 and PIFs do not operate alone, but with the circadian clock. However, sudden changes in light or temperature conditions can trigger changes in HY5 and PIFs abundance that adjust the expression of common target genes to optimise photosynthetic performance and growth

Gibberellin A1 Metabolism Contributes to the Control of Photoperiod-Mediated Tuberization in Potato

Some potato species require a short-day (SD) photoperiod for tuberization, a process that is negatively affected by gibberellins (GAs). Here we report the isolation of StGA3ox2, a gene encoding a GA 3-oxidase, whose expression is increased in the aerial parts and is repressed in the stolons after transfer of photoperiod-dependent potato plants to SD conditions. Over-expression of StGA3ox2 under control of constitutive or leaf-specific promoters results in taller plants which, in contrast to StGA20ox1 over-expressers previously reported, tuberize earlier under SD conditions than the controls. By contrast, StGA3ox2 tuber-specific over-expression results in non-elongated plants with slightly delayed tuber induction. Together, our experiments support that StGA3ox2 expression and gibberellin metabolism significantly contribute to the tuberization time in strictly photoperiod-dependent potato plants

Prevención y diagnóstico precoz de osteoporosis infantil: ¿estamos haciendo lo correcto?

Objetivos: Evaluar la prevención, el diagnóstico precoz y la formación recibida de la osteoporosis en la Pediatría de nuestro medio. Material y métodos: Encuesta dirigida a facultativos de Pediatría de Atención Primaria (AP) y Atención Especializada (AE) que valora su actividad en prevención, detección y formación recibida en osteoporosis, y que fue difundida a través de las sociedades científicas pertinentes. Resultados: Participaron 420 pediatras (324 de AP y 96 de AE). El 93,5% de los pediatras de AP y el 89,6% de los de AE valoraban la actividad física de los pacientes; el 85,19% y 35,4% de ellos, respectivamente, la ingesta de lácteos. El 45,68% de AP y el 70,2% de AE suplementaban con calcio y vitamina D ante aporte nutricional bajo, realizándoles seguimiento el 39,2% de AP y el 47,2% de AE. El 39,6% de pediatras de AE solicitaba densitometría ósea ante enfermedad o tratamiento de riesgo, y el 47,9% medía los niveles de 25-OH-vitamina D. El 25,93% de AP y el 45,3% de AE preguntaban por la existencia de fracturas, el 90,4% y 96,8% valoraban el mecanismo etiopatogénico. El 40% de AP y el 86,2% de AE solicitaban una densitometría ósea o derivaban al especialista ante fracturas por traumatismos de baja energía, con criterios específicos en el 13,7% y 5,86%, respectivamente. El 92% de AP y el 82,3% de AE no habían recibido formación reciente en osteoporosis infantil. Conclusión: La detección, los circuitos de derivación y la formación de los pediatras respecto a la salud ósea en nuestro país es mejorable. Optimizar estos aspectos es fundamental para favorecer el pico de masa ósea en nuestra población

Regulation of carotenoid biosynthesis by shade relies on specific subsets of antagonistic transcription factors and cofactors

Carotenoids are photosynthetic pigments essential for the protection against excess light. During deetiolation, their production is regulated by a dynamic repression-activation module formed by PHYTOCHROME-INTERACTING FACTOR1 (PIF1) and LONG HYPOCOTYL5 (HY5). These transcription factors directly and oppositely control the expression of the gene encoding PHYTOENE SYNTHASE (PSY), the first and main rate-determining enzyme of the carotenoid pathway. Antagonistic modules also regulate the responses of deetiolated plants to vegetation proximity and shade (i.e. to the perception of far-red light-enriched light filtered through or reflected from neighboring plants). These responses, aimed to adapt to eventual shading from plant competitors, include a reduced accumulation of carotenoids. Here, we show that PIF1 and related photolabile PIFs (but not photostable PIF7) promote the shade-triggered decrease in carotenoid accumulation. While HY5 does not appear to be required for this process, other known PIF antagonists were found to modulate the expression of the Arabidopsis (Arabidopsis thaliana) PSY gene and the biosynthesis of carotenoids early after exposure to shade. In particular, PHYTOCHROME-RAPIDLY REGULATED1, a transcriptional cofactor that prevents the binding of true transcription factors to their target promoters, was found to interact with PIF1 and hence directly induce PSY expression. By contrast, a change in the levels of the transcriptional cofactor LONG HYPOCOTYL IN FAR RED1, which also binds to PIF1 and other PIFs to regulate shade-related elongation responses, did not impact PSY expression or carotenoid accumulation. Our data suggest that the fine-regulation of carotenoid biosynthesis in response to shade relies on specific modules of antagonistic transcriptional factors and cofactors

A DELLA in Disguise: SPATULA Restrains the Growth of the Developing Arabidopsis Seedling[C][W]

This study examines the role of the PHYTOCHROME INTERACTING FACTOR3 homolog SPATULA (SPT) in the control of the developing seedling and shows that SPT is a potent regulator of cotyledon size, acting in parallel to DELLAs. As DELLAs negatively regulate SPT abundance, the light regulation of DELLAs drives the DELLA-SPT counterbalance, enforcing growth restraint across a range of ambient light conditions that are prevalent in nature

End of Day FR (EOD-FR) effect over 35S::HA-HY5 and 35S::TAP-PIF1 binding to G-box regions in the promoters of genes related to carotenoids and chlorophyll accumulation at 17°C.

<p>(<b>A</b>) Protein content quantification relative to the signal of UGPase for 35S::HA-HY5, 35S::PIF1-TAP at time 15 h (T15), in samples treated with (+FR) or without (-FR) an EOD saturating FR light pulse (3000 µmol). Triplicate Immunoblots were carried out using 2 week old seedlings. Seedlings were grown for one week in 12 h light/12 h dark white diurnal cycles at 22°C and then transferred to 17°C, 12 h light/12 h dark Red diurnal cycles. Protein was extracted at T15 and quantified against UGPase signal. (<b>B–D</b>) Chromatin Immunoprecipitation assay for <i>PSY</i> (<b>B</b>), <i>LHCA4</i> (<b>C</b>), <i>GUN5</i> (<b>D</b>) and <i>PORC</i> (<b>E</b>) G-box regions in 35S::HA-HY5 and 35S::PIF1-TAP plants treated with (+) or without(−) an EOD FR pulse at T15. +AB indicates samples treated with antibody, -AB stands for no antibody controls. Plants were grown as indicated in (<b>A</b>) and in material and methods. The HA- and MYC- controls and ChIP procedure were described in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004416#pgen-1004416-g004" target="_blank">Figure 4</a>. Error bars represent ± SE of biological triplicates.</p