Hysteresis in PHYTOCHROME-INTERACTING FACTOR 4 and EARLY-FLOWERING 3 dynamics dominates warm daytime memory in Arabidopsis.

Despite the identification of temperature sensors and downstream components involved in promoting stem growth by warm temperatures, when and how previous temperatures affect current plant growth remain unclear. Here we show that hypocotyl growth in Arabidopsis thaliana during the night responds not only to the current temperature but also to preceding daytime temperatures, revealing a short-term memory of previous conditions. Daytime temperature affected the levels of PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) and LONG HYPOCOTYL 5 (HY5) in the nucleus during the next night. These factors jointly accounted for the observed growth kinetics, whereas nighttime memory of prior daytime temperature was impaired in pif4 and hy5 mutants. PIF4 promoter activity largely accounted for the temperature-dependent changes in PIF4 protein levels. Notably, the decrease in PIF4 promoter activity triggered by cooling required a stronger temperature shift than the increase caused by warming, representing a typical hysteretic effect; this hysteretic pattern required EARLY-FLOWERING 3 (ELF3). Warm temperatures promoted the formation of nuclear condensates of ELF3 in hypocotyl cells during the afternoon but not in the morning. These nuclear speckles showed poor sensitivity to subsequent cooling. We conclude that ELF3 achieves hysteresis and drives the PIF4 promoter into the same behavior, enabling a short-term memory of daytime temperature conditions.

Phytochrome B and PCH1 protein dynamics store night temperature information.

Plants experience temperature fluctuations during the course of the daily cycle, and although stem growth responds rapidly to these changes we largely ignore whether there is a short-term memory of previous conditions. Here we show that nighttime temperatures affect the growth of the hypocotyl of Arabidopsis thaliana seedlings not only during the night but also during the subsequent photoperiod. Active phytochrome B (phyB) represses nighttime growth and warm temperatures reduce active phyB via thermal reversion. The function of PHOTOPERIODIC CONTROL OF HYPOCOTYL1 (PCH1) is to stabilise active phyB in nuclear bodies but, surprisingly, warmth reduces PCH1 gene expression and PCH1 stability. When phyB was active at the beginning of the night, warm night temperatures enhanced the levels of nuclear phyB and reduced hypocotyl growth rate during the following day. However, when end-of-day far-red light minimised phyB activity, warm night temperatures reduced the levels of nuclear phyB and enhanced the hypocotyl growth rate during the following day. This complex growth pattern was absent in the phyB mutant. We propose that temperature-induced changes in the levels of PCH1 and in the size of the physiologically relevant nuclear pool of phyB amplify the impact of phyB-mediated temperature sensing.

Non-structural carbohydrates and sugar export in grapevine leaves exposed to different light regimes.

Light is a main environmental factor that determines leaf microclimate within the vine, as well as its photosynthesis and carbohydrate metabolism. This study aimed to examine the relationships between photosynthesis, carbohydrate metabolism, and the expression of related genes in leaves of grapevine grown under different radiation regimes. During the 2014/2015 growing season, an experiment was conducted on a Malbec vineyard (Vitis vinifera L.) in which four radiation exposure treatments were established on the leaves: (1) East, (2) West, (3) Sun, and (4) Shade (i.e., reduction in light intensity). Diurnal dynamics of photosynthesis and non-structural carbohydrates were measured and leaf export rates were calculated. Transcript profiles of leaf sugar transporters (VvHT1, VvHT3, VvSUC27), a sucrose phosphate synthase enzyme (VvSPS), and invertases (VvGIN1, VvCWI) were also examined. We showed that East and Sun leaves had higher daily photosynthetic and export rates than West leaves, which was mainly explained by the environmental conditions (air and leaf temperature, VPDleaf-air ) and leaf water status. Shade leaves accumulated less starch and soluble sugars than exposed leaves, which correlated with a higher expression of hexose transporters and invertases. The hypotheses that these sugars in Shade leaves would play a role as signaling molecules and/or have increased sink strength and phloem unloading are discussed. These results allow us to understand the physiological and molecular behavior of leaves exposed to different radiation regimes, which can be used to design appropriate vineyard management practices.

Factores asociados a mortalidad neonatal en los Hospitales de Santa Bárbara en Intibucá / Factors associated to newborn mortality in the Hospital of Santa Barbara and Intibucá

La mortalidad neonatal es un problema de salud mundial y un indicador de la atención materno infantil. Objetivo: Identificar los factores de riesgo asociados a mortalidad neonatal en pacientes atendidos en los Hos-pitales de Santa Bárbara e Intibucá, de marzo 2017 a febrero 2018. Pacientes y Métodos: Se realizó un estudio cuantitativo, descriptivo, de corte transversal. El Mues-treo fue no probabilístico, con una muestra de 32 pacientes. La recolección de datos fue mediante cuestionario validado por el alfa de Cronbach con fiabilidad de 0.709. Los datos fueron procesados en SPSS versión 22.0. Las variables estudiadas fueron los factores de riesgo socio demográficos, natales, rela-cionados al parto y los asociados al riesgo postnatal de las madres. Resultados: 53% de las madres tenían una edad entre 12 a 19 años; 44% eran analfabetas, 84% de proce-dencia rural y 56% no tuvieron controles prenatales. Asimismo, el 93% presentó vagi-nosis. El porcentaje de neonatos fallecidos en Santa Bárbara fue del 62.5% y en Intibu-cá 37.5%. Conclusión: Los factores de riesgo identificados en mortalidad neonatal fueron el analfabetismo, embarazos en ado-lescentes y ser procedente del área rural.Más de la mitad no tuvieron controles prena-tales y casi todas tuvieron vaginosis. Las causas de muerte neonatal fueron: sepsis, prematurez, asfixia, síndrome de aspiración meconial y malformaciones congénitas...(AU)

ABA and GA3 increase carbon allocation in different organs of grapevine plants by inducing accumulation of non-structural carbohydrates in leaves, enhancement of phloem area and expression of sugar transporters.

Grape quality for winemaking depends on sugar accumulation and metabolism in berries. Abscisic acid (ABA) and gibberellins (GAs) have been reported to control sugar allocation in economically important crops, although the mechanisms involved are still unknown. The present study tested if ABA and gibberellin A3 (GA3) enhance carbon allocation in fruits of grapevines by modifying phloem loading, phloem area and expression of sugar transporters in leaves and berries. Pot-grown Vitis vinifera cv. Malbec plants were sprayed with ABA and GA3 solutions. The amount of soluble sugars in leaves and berries related to photosynthesis were examined at three points of berry growth: pre-veraison, full veraison and post-veraison. Starch levels and amylase activity in leaves, gene expression of sugar transporters in leaves and berries and phloem anatomy were examined at full veraison. Accumulation of glucose and fructose in berries was hastened in ABA-treated plants at the stage of full veraison, which was correlated with enhancement of Vitis vinifera HEXOSE TRANSPORTER 2 (VvHT2) and Vitis vinifera HEXOSE TRANSPORTER 6 (VvHT6) gene expression, increases of phloem area and sucrose content in leaves. On the other hand, GA3 increased the quantity of photoassimilates delivered to the stem thus increasing xylem growth. In conclusion, stimulation of sugar transport by ABA and GA3 to berries and stems, respectively, was due to build-up of non-structural carbohydrates in leaves, modifications in phloem tissue and modulation in gene expression of sugar transporters.