Molecular Biology of Sugar Transporters in Plants

Both lower and higher plants have been shown to possess efficient transport systems for the uptake of sugars across the plasmalemma. Genes encoding transport proteins for both mono- and disaccharides have been cloned recently. The main cloning strategies — differential screening, complementation cloning in Saccharomyces cerevisiae, and heterologous screening — are briefly summarized. The relationship of plant sugar transporters to a superfamily of more than 50 uni-, sym-, and antiporters cloned so far is discussed. Various possibilities for heterologous expression (in Schizosaccharomyces pombe, Saccharomyces cerevisiae, Xenopus oocytes) of plant sugar transporters are described and compared. Eight D-glucose transporters (from yeast to Arabidopsis to man) only possess 7% identical amino acids. First site-directed mutations of the Chlorella HUP1 transporter indicate that at least transmembrane helices 5, 7 and 11 line the D-glucose specific path through the membrane. The genomic structures of two plant transporters are outlined; the glycosylation of transport proteins as well as their tissue specificity is discussed.     

显花植物自体和异体花粉识别的分子机理研究(英文)

显花植物的受精涉及许多识别过程;其中第一个是雌性生殖组织心皮对花粉的识别。自交不亲和性（Ｓｅｌｆ－ｉｎｃｏｍｐａｔｉｂｉｌｉｔｙ,ＳＩ）是一种广泛分布于显花植物的种内生殖障碍。在多数自交不亲和的植物中,ＳＩ的遗传控制比较简单,受控于一个由复等位基因构成的单一位点,称为Ｓ位点。在以茄科、玄参科和蔷薇科为代表的配子体自交不亲和植物中,Ｓ位点编码一类核酸酶,即Ｓ核酸酶（Ｆｉｇ．１）,控制ＳＩ在花柱中的表达,但是与花粉自交不亲和性的表达无关。后者可能由与Ｓ核酸酶不同的基因控制,这种基因常被称为花粉Ｓ基因。它是目前了解显花植物花粉识别生化和分子机理的关键。近来;通过对影响花粉ＳＩ表达突变体的分子遗传分析提出了一个花粉Ｓ基因产物如何与Ｓ核酸酶相互作用完成自体和异体花粉识别过程的模型（Ｆｉｇ．２）。另外,描述了两个在金鱼草中克隆花粉Ｓ基因的方法,即Ｓ位点选择性的转座子标记和图位克隆。     

Diverse Ways to Control p27Kip1 Function: miRNAs Come into Play

microRNAs (miRNAs) are small RNA molecules controlling messenger RNA (mRNA) and protein abundance. Since their discovery, research has been aimed at identifying the functions and target genes of miRNAs. A number of computer algorithms have been developed capable of predicting putative targets for any given miRNA. However, they might predict many false-positive targets and on top of that some true targets could be missed. This reflects the incomplete knowledge we still have concerning the rules governing true and effective miRNA-mRNA interactions. To experimentally identify miRNA-target genes, we have recently developed a genetic approach and employed it on p27Kip1, a hapo-insufficient tumor suppressor and cell cycle inhibitor. Here we review the difficulties interpreting the data from available computer algorithms, and critically address the pros and cons of our genetic screening method. Additionally, we focus on the different ways in which p27 is managed, argue how miRNAs could be involved in the regulation of p27 in both normal and malignant conditions, and discuss possible use of this knowledge for cancer therapy.     

The Home Dreams and Waking Fantasies of Boys and Girls Between Ages 9 and 15: A Longitudinal Study

In this longitudinal developmental study, 12 boys and 12 girls provided home dreams and waking fantasies at 3 age levels: 9–11, 11–13, and 13–15. A total of 299 dreams and 286 fantasies were coded by 2 independent raters using Hall and Van de Castle (1966) content categories. In addition, word counts and bizarreness ratings were completed. There were very few changes in the dreams or waking fantasies of either boys or girls, but dream reports were longer at ages 13–15, the aggression/friendliness percent increased over the course of the study, joint-sex peer groups became more frequent, and girls showed a decline in animal percent. The tendency in a wide range of societies for men to dream mostly about other men and for women to dream equally of women and men was found in both the dreams and waking fantasies. Dreams and fantasies differed markedly, with dreams containing more outdoor and unfamiliar settings, and more bizarreness. In dreams the children tended to portray themselves as victims of aggression and recipients of friendliness, but in fantasies they took a more active role as aggressors and befrienders. It is suggested that the children in this study portrayed themselves in their dreams as they conceived of themselves in everyday life, while in their waking fantasies they imagined themselves as they would have liked to be.     

植物离子通道特征、功能、调节与分子生物学

本文对植物离子通道的特征、生理功能、影响通道启闭的因素和通道分子生物学研究的新进展作了较为系统的综述。     

Practice Variation in the Management of Girls and Boys with Delayed Puberty

Objective: Delayed puberty is a common condition, and typical management includes “watchful waiting” and/or sex-steroid therapy. We sought to characterize treatment practices and to assess provider comfort with the management of delayed puberty in girls and boys.Methods: A national survey of pediatric endocrine providers assessed definitions of delayed puberty, practices around sex-steroid therapy, reasons for treatment, and comfort in managing delayed puberty in girls and boys.Results: Of 184 respondents (12% participation rate), 64% and 71% used the traditional age cutoffs for defining delayed puberty of 13 years for girls and 14 years for boys, respectively. Nearly half (45%) of providers would treat boys relatively earlier than girls, compared to 18% who would treat girls relatively earlier (P<.0001). Providers were more likely to cite bone density as a reason to treat girls and alleviating patient and parental distress, accelerating growth, and “jump starting” puberty as reasons to treat boys. Greater experience in endocrine practice was associated with greater comfort managing delayed puberty in both boys and girls. Approximately 80% of providers agreed that clinical guidelines are needed for the management of delayed puberty.Conclusion: There is a high degree of variability in the clinical management of delayed puberty, and our results suggest that providers are more hesitant to treat girls compared to boys and have different reasons for treating each. It remains to be determined if these discrepancies in treatment are justified by biologic differences between girls and boys or represent nonevidence-based disparities in care.Abbreviation: U.S. = United States     

Evaluation of Metabolic Risk in Prepubertal Girls Versus Boys in Relation to Fitness and Physical Activity

BackgroundLow levels of cardiorespiratory fitness (CRF) and physical activity (PA) are associated with a risk of the development of metabolic syndrome. Contradictory findings are reported in the literature regarding the influence of sex and CRF and PA on metabolic changes.ObjectiveThe aim of this study was to analyze the effects of CRF and PA on lipid and carbohydrate metabolism biomarkers in boys and girls.MethodsA total of 82 prepubertal boys and 55 girls (7–12 years of age) were classified according to sex, low or high CRF, and performance or nonperformance of PA. Anthropometric and blood pressure (BP) measurements, plasma lipid profile values, glucose and insulin levels, and homeostasis model assessment for insulin resistance were analyzed.ResultsThe percentage of boys with high CRF and performance of PA was higher than that of girls (P < 0.05). When children of the same sex were compared, higher values for body mass index and waist circumference z-scores were found for boys with low CRF compared with boys with high CRF (P < 0.001) without differences between girls, and in all groups classified by PA. Systolic and diastolic BPs were higher in boys than in girls, in both CRF and PA groups (P < 0.05). In the low CRF and no PA groups, girls had higher plasma glucose, total cholesterol, and low-density lipoprotein cholesterol levels than boys, with higher high-density lipoprotein cholesterol and apolipoprotein A levels (P < 0.05).ConclusionsSex in relation to CRF and PA could affect the plasma lipid profile. These changes in girls are associated with low CRF and low levels of PA. Considering these results, we suggest the need to improve CRF and promote PA, especially in girls, to reduce metabolic risk.