Twofold effect of blue light on a circadian rhythm in Acetabularia

Abstract

The circadian chloroplast migration in Acetabularia mediterranea was monitored by continuously measuring the transmission of the cells near the apex. Under continuous red light the amplitude of the rhythm decreased rapidly within a few days. However, circadian changes of chloroplast density were still detectable even after 28 days of red light, indicating the persistence of the rhythm. When blue light was added after red light preirradiation of several days phase shifts were observed which were expressed as advances as well as delays. The period of the rhythm proved to be strongly dependent on the intensity of the continuous blue light which was given in addition to red light. Different red light intensities did not change the period. The occurrence of both effects indicates that the sensory transduction of blue light photoreception in Acetabularia works in two different ways: quanta counting processes and processes of light intensity measurement.     

Dye affinity chromatography for fast and simple purification of fucoidan from marine brown algae

Fucoidan is a sulfated polysaccharide with promising pharmacological applications. Due to its medicinal properties, there is a demand for a separation technique that yields a high purification grade. Here, we present a novel purification tool for recovering fucoidan from the marine brown macroalgae Fucus vesiculosus. The developed method is based on amino‐derivatized Sepabeads^® EC‐EA. The beads were modified with toluidine blue (TB), a thiazine derivative, to exploit the strong donor acceptor interactions between the cationic dye and the anionic polysaccharide. The adsorption kinetics and the binding capacity of the resin were analyzed. A Sips model was used to approximate the adsorption isotherm, resulting in a maximum capacity of 127.7 mg fucoidan per g adsorbent. Investigation of the effect of adsorption step's pH on purity and chemical structure was performed by TB and Fourier transform infra‐red spectroscopy assays. Results showed that adsorption at pH 1 and 6 had negligible effects on fucoidan's chemical structure. However, purity was actually improved by 1.55‐ and 1.69‐fold at pH 1 and 6, respectively, with an average yield of 5 g/100 g dried algae powder. In contrast, only a 1.46‐fold increment was observed in fucoidan purified by the traditional method at pH 2, with a yield of 7.5 g/100 g dried algae powder. Furthermore, fucoidan purified by this method at pH 6 complies with, or even exceeds the quality of the commercially available (≥95% pure) fucoidan (Sigma‐Aldrich^®) with respect to molecular weight and sulfur content. Therefore, dye affinity chromatography provides more advantages than the classically used techniques for fucoidan purification.     

Design and characterization of electrochemical dopamine–aptamer as convenient and integrated sensing platform

Here, an ultrasensitive label-free electrochemical aptasensor was developed for dopamine (DA) detection. Construction of the aptasensor was carried out by electrodeposition of gold–platinum nanoparticles (Au–PtNPs) on glassy carbon (GC) electrode modified with acid-oxidized carbon nanotubes (CNTs–COOH). A designed complementary amine-capped capture probe (ssDNA1) was immobilized at the surface of PtNPs/CNTs–COOH/GC electrode through the covalent amide bonds formed by the carboxyl groups on the nanotubes and the amino groups on the oligonucleotides. DA-specific aptamer was attached onto the electrode surface through hybridization with the ssDNA1. Methylene blue (MB) was used as an electrochemical indicator that was intercalated into the aptamer through the specific interaction with its guanine bases. In the presence of DA, the interaction between aptamer and DA displaced the MB from the electrode surface, rendering a lowered electrochemical signal attributed to a decreased amount of adsorbed MB. This phenomenon can be applied for DA detection. The peak current of probe (MB) linearly decreased over a DA concentration range of 1–30 nM with a detection limit of 0.22 nM.     

Different climate response of three tree ring proxies of Pinus sylvestris from the Eastern Carpathians,Romania

The aim of this study was to compare the climatic responses of three tree rings proxies: tree ring width (TRW), maximum latewood density (MXD), and blue intensity (BI). For this study, 20 cores of Pinus sylvestris covering the period 1886–2015 were extracted from living non-damaged trees from the Eastern Carpathian Mountains (Romania). Each chronology was compared to monthly and daily climate data. All tree ring proxies had a stronger correlation with the daily climate data compared to monthly data. The highest correlation coefficient was obtained between the MXD chronology and daily maximum temperature over the period beginning with the end of July and ending in the middle of September (r = 0.64). The optimal intervals for the temperature signature were 01 Aug – 24 Sept for the MXD chronology, 05 Aug – 25 Aug for the BI chronology, and both 16 Nov of the previous year – 16 March of the current year and 15 Apr – 05 May for the TRW chronology. The results from our study indicate that MXD can be used as a proxy indicator for summer maximum temperature, while TRW can be used as a proxy indicator for just March maximum temperature. The weak and unstable relationship between BI and maximum temperature indicates that BI is not a good proxy indicator for climate reconstructions over the analysed region.     

Fluorescence in blue light (FLU) is involved in inactivation and localization of glutamyl‐tRNA reductase during light exposure

Fluorescent in blue light (FLU) is a negative regulator involved in dark repression of 5‐aminolevulinic acid (ALA) synthesis and interacts with glutamyl‐tRNA reductase (GluTR), the rate‐limiting enzyme of tetrapyrrole biosynthesis. In this study, we investigated FLU‘s regulatory function in light‐exposed FLU‐overexpressing (FLUOE) Arabidopsis lines and under fluctuating light intensities in wild‐type (WT) and flu seedlings. FLUOE lines suppress ALA synthesis in the light, resulting in reduced chlorophyll content, but more strongly in low and high light than in medium growth light. This situation indicates that FLU's impact on chlorophyll biosynthesis depends on light intensity. FLU overexpressors contain strongly increased amounts of mainly membrane‐associated GluTR. These findings correlate with FLU‐dependent localization of GluTR to plastidic membranes and concomitant inhibition, such that only the soluble GluTR fraction is active. The overaccumulation of membrane‐associated GluTR indicates that FLU binding enhances GluTR stability. Interestingly, under fluctuating light, the leaves of flu mutants contain less chlorophyll compared with WT and become necrotic. We propose that FLU is basically required for fine‐tuned ALA synthesis. FLU not only mediates dark repression of ALA synthesis, but functions also to control balanced ALA synthesis under variable light intensities to ensure the adequate supply of chlorophyll.     

吉林老白山鱼鳞云杉树轮蓝光强度和轮宽指数与气候响应关系随海拔变化的对比

树轮数据是晚全新世古气候研究中最重要的代用指标。树轮参数各具优缺点, 蓝光强度(BI)是一种获取成本低廉的最大晚材密度(MXD)的光学替代参数, 其蓝色光反射率或强度最小值(256-BI)与相应的MXD值高度相关, 被很多的学者认为是树轮气候学研究中一个具有重要潜能的新兴参数。该研究以吉林老白山3个海拔(900、1 200和1 500 m)的鱼鳞云杉(Picea jezoensis)为例, 分析鱼鳞云杉的BI及轮宽指数(RWI)与气候因子的响应差异, 以期为BI参数在树轮气候学的进一步应用提供参考。结果表明: 不同海拔鱼鳞云杉BI或RWI对气候的响应趋势基本一致。BI与温度主要呈正相关关系, 而RWI与温度主要呈负相关关系, 其中BI与当年夏季及生长季最高温度显著正相关, 而RWI (低、中海拔)与全年平均气温、当年生长季和全年最低温度显著负相关。BI与当年夏季标准化降水蒸散指数(SPEI)显著负相关, RWI与夏季SPEI负相关关系较弱或为正相关; BI和RWI几乎相反的生长-气候关系可能是早、晚材权衡关系的体现。研究区域鱼鳞云杉的BI参数可能与年轮宽度记录不同的气候信号, 在空间尺度上对于当年夏季降水、最高温度以及SPEI的响应好于传统宽度指标。BI与主要气候因子相关关系的时间稳定性好于RWI, 因此, BI在树轮气候学的研究中具有一定的应用潜能。