Diversity in the carotenoid profiles and the expression of genes related to carotenoid accumulation among citrus genotypes

Carotenoids are not only important to the plants themselves but also are beneficial to human health. Since citrus fruit is a good source of carotenoids for the human diet, it is important to study carotenoid profiles and the accumulation mechanism in citrus fruit. Thus, in the present paper, we describe the diversity in the carotenoid profiles of fruit among citrus genotypes. In regard to carotenoids, such as β-cryptoxanthin, violaxanthin, lycopene, and β-citraurin, the relationship between the carotenoid profile and the expression of carotenoid-biosynthetic genes is discussed. Finally, recent results of quantitative trait locus (QTL) analyses of carotenoid contents and expression levels of carotenoid-biosynthetic genes in citrus fruit are shown.     

Carotenoid production by the marine microalgae Nannochloropsis oculata in different low‐cost culture media

Nannochloropsis oculata (Eustigmatophyceae) is a marine microalga of great biotechnological interest, mainly due to its large production of lipids containing polyunsaturated fatty acids. In addition, this species presents a wide range of commercial interest pigments, such as zeaxanthin, beta‐carotene, and other xanthophylls, with potential for several industrial applications. However, most of the research concerning pigment production by N. oculata has been conducted by employing high‐cost laboratorial growth media, which makes large‐scale pigment production using these microalgae impractical. Considering the high interest and commercial value in microalgae pigments, this study investigates the feasibility of producing pigments by N. oculata using five different low‐cost growth media (fertilizers and aquaculture effluents). Nutrient (ammonia, nitrite and phosphate) concentrations, cell abundance, biomass, and the concentration/composition of pigments were measured. The pigment profile of N. oculata showed chlorophyll‐a as the dominant pigment, along with violaxanthin, vaucheraxanthin, and lower concentrations of antheraxanthin, zeaxanthin and beta‐carotene. Although the highest biomass (516.4 ± 76.71 mg/L) and pigment content (0.98 mg/g) were achieved in the laboratory media (f/2), the low‐cost media (containing ammonium sulfate, calcium superphosphate and urea) revealed a great potential for the production of pigments, specially chlorophyll‐a, violaxanthin and zeaxanthin, due to the high pigment content per unit of biomass.     

VDE基因在植物抗逆响应中的功能

叶黄素循环存在于高等植物和绿色藻类,是保护植物光合机构免受过剩光能破坏的重要机制。作为叶黄素循环关键酶,紫黄质脱环氧化酶(VDE)可催化双脱氧紫黄质(V)脱环氧化成单环氧玉米黄质(A)进而生成玉米黄质(Z),保护光合器官免受过剩光能破坏。VDE活性受多种因素调节,在非生物胁迫下,植物多种叶绿素荧光等指标均受影响,近期利用过表达、突变体与野生型植株对比研究进一步揭示VDE基因在植物生长中的重要作用。文章综述近年来有关VDE在植物抗逆生理中的功能研究进展。     

植物紫黄素脱环氧化酶结构特征的生物信息学分析

利用国际互联网上的生物学数据库(GenBank,Swiss-Prot和Prosite)所提供的信息资源和工具(PHDsec 和SignalP)及软件技术(DNAstar),从生物信息学角度对植物紫黄素脱环氧化酶(VDE)进行序列的比较分析和结构预测,得出了其转运肽特征、相关保守位点和特殊结构域以及序列的二级结构特征,并对其进行了相应功能的探讨.     

低温强光下水稻类囊体膜脂不饱和度和叶黄素循环组分的变化

为了阐明籼稻、粳稻对低温强光敏感性的差异,着重研究了低温强光下水稻类囊体膜脂不饱和度与紫黄质脱环氧化酶（VDE）活性的变化。随着低温强光处理时间的延长,类囊体膜脂不饱和脂肪酸含量降低、饱和脂肪酸含量增加,因而膜脂不饱和指数(IUFA)下降。同时,叶黄素循环的关键酶——VDE活性降低,叶黄素循环组分中紫黄质（V）含量增加,而单环氧玉米黄质（A）和玉米黄质（Z）的含量减少,表现为(A+Z)/(A+Z+V)比值下降。Arrhenius分析证明,VDE对低温和膜脂不饱和度都敏感。相关分析表明,类囊体IUFA分别与VDE活性、(A+Z)/(A+Z+V)和D1蛋白量呈显著的正相关。与粳稻9516相比,籼稻汕优63类囊体膜的IUFA较低,低温下类囊体膜脂流动性和稳定性较差, VDE活性和(A+Z)/(A+Z+V)比值较低。     

Antiproliferative activity of violaxanthin isolated from bioguided fractionation of Dunaliella tertiolecta extracts

Dunaliella tertiolecta (DT) was chemically investigated to isolate molecules inhibiting cancer cell proliferation and inducing apoptosis in vitro. The potency to inhibit cell growth was used for the bio-guided fractionation and isolation of active compounds using chromatographic techniques. The DT dichloromethane extract exhibited a strong anti-proliferative activity on MCF-7 and LNCaP cells, and was further fractionated and sub-fractionated by RP-HPLC. High resolution mass spectrometry and spectrophotometric analysis unequivocally identified violaxanthin as the most antiproliferative molecule present in DT DCM extract. Violaxanthin purified from DT induced MCF-7 dose-dependent growth inhibition in continuous and discontinuous treatments, at concentrations as low as 0.1 μg·mL⁻¹ (0.17 μM). Phosphatidylserine exposure, typical of early apoptosis, was observed after 48 h treatment at 8 μg·mL⁻¹ (13.3 μM) but no DNA fragmentation, characteristic of late apoptosis steps, could be detected even after 72 h treatment at 40 μg·mL⁻¹ (66.7 μM). Taken together, our results demonstrate the strong antiproliferative activity of violaxanthin on one human mammary cancer cell line, and suggest that studying the pharmacology of violaxanthin and pharmacomodulated derivatives on cancer cells may allow potent antiproliferative drugs to be obtained.