Expression analysis of the AtPHO1 gene family in Arabidopsis thaliana and the involvement of AtPHO1 in the regulation of stomatal movements

Résumé Le transfert du phosphate des racines vers les feuilles s'effectue par la voie du xylème. Il a été précédemment démontré que la protéine AtPHO1 était indispensable au transfert du phosphate dans les vaisseaux du xylème des racines chez la plante modèle Arabidopsis thaliana. Le séquençage et l'annotation du génome d'Arabidopsis ont permis d'identifier dix séquences présentant un niveau de similarité significatif avec le gène AtPHO1 et constituant une nouvelle famille de gène appelé la famille de AtPHO1. Basée sur une étude moléculaire et génétique, cette thèse apporte des éléments de réponse pour déterminer le rôle des membres de ia famille de AtPHO1 chez Arabidopsis, inconnue à ce jour. Dans un premier temps, une analyse bioinformatique des séquences protéiques des membres de la famille de AtPHO1 a révélé la présence dans leur région N-terminale d'un domaine nommé SPX. Ce dernier est conservé parmi de nombreuses protéines impliquées dans l'homéostasie du phosphate chez la levure, renforçant ainsi l'hypothèse que les membres de la famille de AtPHO1 auraient comme AtPHO1 un rôle dans l'équilibre du phosphate dans la plante. En parallèle, la localisation tissulaire de l'expression des gènes AtPHO dans Arabidopsis a été identifiée par l'analyse de plantes transgéniques exprimant le gène rapporteur uidA sous le contrôle des promoteurs respectifs des gènes AtPHO. Un profil d'expression de chaque gène AtPHO au cours du développement de la plante a été obtenu. Une expression prédominante au niveau des tissus vasculaires des racines, des feuilles, des tiges et des fleurs a été observée, suggérant que les gènes AtPHO pourraient avoir des fonctions redondantes au niveau du transfert de phosphate dans le cylindre vasculaire de ces différents organes. Toutefois, plusieurs régions promotrices des gènes AtPHO contrôlent également un profil d'expression GUS non-vasculaire, indiquant un rôle putatif des gènes AtPHO dans l'acquisition ou le recyclage de phosphate dans la plante. Dans un deuxième temps, l'analyse de l'expression des gènes AtPHO durant une carence en phosphate a établi que seule l'expression des gènes AtPHO1, AtPHO1; H1 et AtPHO1; H10 est régulée par cette carence. Une étude approfondie de leur expression en réponse à des traitements affectant l'homéostasie du phosphate dans la plante a ensuite démontré leur régulation par différentes voies de signalisation. Ensuite, une analyse détaillée de la régulation de l'expression du gène AtPHO1; H1O dans des feuilles d'Arabidopsis blessées ou déshydratées a révélé que ce gène constitue le premìer gène marqueur d'une nouvelle voie de signalisation induite par l'OPDA, pas par le JA et dépendante de la protéine COI1. Ces résultats démontrent pour la première fois que l'OPDA et le JA peuvent activer différents gènes via des voies de signalisation dépendantes de COI1. Enfin, cette thèse révèle l'identification d'un nouveau rôle de la protéine AtPHO1 dans la régulation de l'action de l'ABA au cours des processus de fermeture stomatique et de germination des graines chez Arabidopsis. Bien que les fonctions exactes des protéines AtPHO restent à être déterminées, ce travail de thèse suggère leur implication dans la propagation de différents signaux dans la plante via la modulation du potentiel membranaire et/ou l'affectation de la composition en ions des cellules comme le font de nombreux transporteurs ou régulateur du transport d'ions. Summary Phosphate is transferred from the roots to the shoot via the xylem. The requirement for AtPHO1 protein to transfer phosphate to the xylem vessels of the root has been previously demonstrated in Arabidopsis thaliana. The sequencing and the annotation of the Arabidopsis genome had allowed the identification of ten sequences that show a significant level of similarity with the AtPHO1 gene. These 10 genes, of unknown functions, constitute a new gene family called the AtPHO1 gene family. Based on a molecular and genetics study, this thesis reveals some information needed to understand the role of the AtPHO1 family members in the plant Arabidopsis. First, a bioinformatics study revealed that the AtPHO sequences contained, in the N-terminal hydrophilic region, a motif called SPX and conserved among multiple proteins involved in phosphate homeostasis in yeast. This finding reinforces the hypothesis that all AtPHO1 family members have, as AtPHO1, a role in phosphate homeostasis. In parallel, we identified the pattern of expression of AtPHO genes in Arabidopsis via analysis of transgenic plants expressing the uidA reporter gene under the control of respective AtPHO promoter regions. The results exhibit a predominant expression of AtPHO genes in vascular tissues of all organs of the plant, implying that these AtPHO genes could have redundant functions in the transfer of phosphate to the vascular cylinder of various organs. The GUS expression pattern for several AtPHO promoter regions was also detected in non-vascular tissue indicating a broad role of AtPHO genes in the acquisition or in the recycling of phosphate in the plant. In a second step, the analysis of the expression of AtPHO genes during phosphate starvation established that only the expression of the AtPHO1, AtPHO1; H1 and AtPHO1; H10 genes were regulated by Pi starvation. Interestingly, different signalling pathways appeared to regulate these three genes during various treatments affecting Pi homeostasis in the plant. The third chapter presents a detailed analysis of the signalling pathways regulating the expression of the AtPHO1; H10 gene in Arabidopsis leaves during wound and dehydrated stresses. Surprisingly, the expression of AtPHO1; H10 was found to be regulated by OPDA (the precursor of JA) but not by JA itself and via the COI1 protein (the central regulator of the JA signalling pathway). These results demonstrated for the first time that OPDA and JA could activate distinct genes via COI1-dependent pathways. Finally, this thesis presents the identification of a novel role of the AtPHO1 protein in the regulation of ABA action in Arabidopsis guard cells and during seed germination. Although the exact role and function of AtPHO1 still need to be determined, these last findings suggest that AtPHO1 and by extension other AtPHO proteins could mediate the propagation of various signals in the plant by modulating the membrane potential and/or by affecting cellular ion composition, as it is the case for many ion transporters or regulators of ion transport.

Collagen, convulxin, and thrombin stimulate aggregation-independent tyrosine phosphorylation of CD31 in platelets. Evidence for the involvement of Src family kinases

Platelet endothelial cell adhesion molecule-1 (CD31) is a 130-kDa glycoprotein receptor present on the surface of platelets, neutrophils, monocytes, certain T-lymphocytes, and vascular endothelial cells. CD31 is involved in adhesion and signal transduction and is implicated in the regulation of a number of cellular processes. These include transendothelial migration of leukocytes, integrin regulation, and T-cell function, although its function in platelets remains unclear. In this study, we demonstrate the ability of the platelet agonists collagen, convulxin, and thrombin to induce tyrosine phosphorylation of CD31. Furthermore, we show that this event is independent of platelet aggregation and secretion and is accompanied by an increase in surface expression of CD31. A kinase capable of phosphorylating CD31 was detected in CD31 immunoprecipitates, and its activity was increased following activation of platelets. CD31 tyrosine phosphorylation was reduced or abolished by the Src family kinase inhibitor PP2, suggesting a role for these enzymes. In accordance with this, each of the Src family members expressed in platelets, namely Fyn, Lyn, Src, Yes, and Hck, was shown to co-immunoprecipitate with CD31. The involvement of Src family kinases in this process was confirmed through the study of mouse platelets deficient in Fyn.

Family food involvement and frequency of famiy dinner meals among Australian children aged 10-12 years. Cross-sectional and longitudinal associations with dietary patterns

Involvement in meal preparation and eating meals with the family are associated with better dietary patterns in adolescents, however little research has included older children or longitudinal study designs. This 3-year longitudinal study examines cross-sectional and longitudinal associations between family food involvement, family dinner meal frequency and dietary patterns during late childhood. Questionnaires were completed by parents of 188 children from Greater Melbourne, Australia at baseline in 2002 (mean age = 11.25 years) and at follow-up in 2006 (mean age = 14.16 years). Principal components analysis (PCA) was used to identify dietary patterns. Factor analysis (FA) was used to determine the principal factors from six indicators of family food involvement. Multiple linear regression models were used to predict the dietary patterns of children and adolescents at baseline and at follow-up, 3 years later, from baseline indicators of family food involvement and frequency of family dinner meals. PCA revealed two dietary patterns, labeled a healthful pattern and an energy-dense pattern. FA revealed one factor for family food involvement. Cross-sectionally among boys, family food involvement score (β = 0.55, 95% CI: 0.02, 1.07) and eating family dinner meals daily (β = 1.11, 95% CI: 0.27, 1.96) during late childhood were positively associated with the healthful pattern. Eating family dinner meals daily was inversely associated with the energy-dense pattern, cross-sectionally among boys (β = −0.56, 95% CI: −1.06, −0.06). No significant cross-sectional associations were found among girls and no significant longitudinal associations were found for either gender. Involvement in family food and eating dinner with the family during late childhood may have a positive influence on dietary patterns of boys. No evidence was found to suggest the effects on dietary patterns persist into adolescence.

Exploring family and community involvement to protect Thai youths from alcohol and illegal drug abuse

Youth substance abuse is widely recognized as a major public health issue in Thailand. This study explores family and community risk and protective factors relevant to alcohol and illegal drug misuse in 1,778 Thai teenagers. Strong family attachment and a family history of antisocial behaviors were strongly associated with nearly all forms of substance abuse, with adjusted odds ratios ranging from 5.05 to 8.45. Community disorganization was strongly associated with self-reported substance use, although involvement in prosocial activities acted as a protective factor. The findings suggest that interventions that promote family cohesion and encourage community involvement may have considerable benefits in reducing substance abuse in Thai adolescents.

Molecular cloning of a family of xenobiotic-inducible drosophilid cytochrome P450s: Evidence for involvement in host-plant allelochemical resistance

Cytochrome P450s constitute a superfamily of genes encoding mostly microsomal hemoproteins that play a dominant role in the metabolism of a wide variety of both endogenous and foreign compounds. In insects, xenobiotic metabolism (i.e., metabolism of insecticides and toxic natural plant compounds) is known to involve members of the CYP6 family of cytochrome P450s. Use of a 3′ RACE (rapid amplification of cDNA ends) strategy with a degenerate primer based on the conserved cytochrome P450 heme-binding decapeptide loop resulted in the amplification of four cDNA sequences representing another family of cytochrome P450 genes (CYP28) from two species of isoquinoline alkaloid-resistant Drosophila and the cosmopolitan species Drosophila hydei. The CYP28 family forms a monophyletic clade with strong regional homologies to the vertebrate CYP3 family and the insect CYP6 family (both of which are involved in xenobiotic metabolism) and to the insect CYP9 family (of unknown function). Induction of mRNA levels for three of the CYP28 cytochrome P450s by toxic host-plant allelochemicals (up to 11.5-fold) and phenobarbital (up to 49-fold) corroborates previous in vitro metabolism studies and suggests a potentially important role for the CYP28 family in determining patterns of insect–host-plant relationships through xenobiotic detoxification.

Increasing male involvement in family planning decision making: trial of a social-cognitive intervention in rural Vietnam

We tested a social-cognitive intervention to influence contraceptive practices among men living in rural communes in Vietnam. It was predicted that participants who received a stage-targeted program based on the Transtheoretical Model (TTM) would report positive movement in their stage of motivational readiness for their wife to use an intrauterine device (IUD) compared to those in a control condition. A quasi-experimental design was used, where the primary unit for allocation was villages. Villages were allocated randomly to a control condition or to two rounds of intervention with stage-targeted letters and interpersonal counseling. There were 651 eligible married men in the 12 villages chosen. A significant positive movement in men's stage of readiness for IUD use by their wife occurred in the intervention group, with a decrease in the proportions in the precontemplation stage from 28.6 to 20.2% and an increase in action/maintenance from 59.8 to 74.4% (P < 0.05). There were no significant changes in the control group. Compared to the control group, the intervention group showed higher pros, lower cons and higher self-efficacy for IUD use by their wife as a contraceptive method (P < 0.05). Interventions based on social-cognitive theory can increase men's involvement in IUD use in rural Vietnam and should assist in reducing future rates of unwanted pregnancy.

Generative acts: Family and community involvement of older Australians

The article adopts a developmental approach to successful human aging by exploring the concept of generativity in relation to a study of older Australians' lived experiences of involvement in the family and community. Qualitative data, collected through focus group interviews, were analyzed interpretively using recent developments in Erikson's theory of generativity as a framework. As a result, the present study contributes an in-depth understanding of the role of generative acts to the lives of older people. The data provide illustrative support for Erikson's contention of a generativity/stagnation crisis in later life. Involvement in the family and community is seen as a productive and generative activity, which promotes a positive experience of aging. Two further emergent themes are also explored. First, the experiences of study participants illustrate the reciprocal and cyclical nature of grand-generativity, and the importance of intergenerational relationships. Finally, the data contribute to our knowledge of cultural generativity, and in particular the passing on of cultural knowledge through narratives and modeling.

The Expanded Human Kallikrein (KLK) gene family : genomic organisation, tissue specific expression and potential functions

The tissue kallikreins are serine proteases encoded by highly conserved multigene families. The rodent kallikrein (KLK) families are particularly large, consisting of 13 26 genes clustered in one chromosomal locus. It has been recently recognised that the human KLK gene family is of a similar size (15 genes) with the identification of another 12 related genes (KLK4-KLK15) within and adjacent to the original human KLK locus (KLK1-3) on chromosome 19q13.4. The structural organisation and size of these new genes is similar to that of other KLK genes except for additional exons encoding 5 or 3 untranslated regions. Moreover, many of these genes have multiple mRNA transcripts, a trait not observed with rodent genes. Unlike all other kallikreins, the KLK4-KLK15 encoded proteases are less related (25–44%) and do not contain a conventional kallikrein loop. Clusters of genes exhibit high prostatic (KLK2-4, KLK15) or pancreatic (KLK6-13) expression, suggesting evolutionary conservation of elements conferring tissue specificity. These genes are also expressed, to varying degrees, in a wider range of tissues suggesting a functional involvement of these newer human kallikrein proteases in a diverse range of physiological processes.

Torres Strait Islander parents’ involvement in their children’s mathematics learning : a discussion paper

This paper is a beginning point for discussing what the literature states about parents’ involvement in their children’s mathematics education. Where possible it will focus on Torres Strait Islander Peoples. Little is known about how Torres Strait Islander parents approach their children’s learning of mathematics and how important early mathematics is to mothers. What is known is that is they are keen for their children to receive an education that provides them with opportunities for their present and future lives. However, gaining access to education is challenging given that the language of instruction in schools is written to English conventions, decontextualised and disconnected from the students’ culture, community and home language. This paper discusses some of the issues raised in the literature about what parents are confronted with when making decisions about their children’s education.

Torres Strait Island parents' involvement in their children's mathematics learning : a discussion paper

This paper is a beginning point for discussing what the literature states about parents’ involvement in their children’s mathematics education. Where possible it will focus on Torres Strait Islander Peoples. Little is known about how Torres Strait Islander parents approach their children’s learning of mathematics and how important early mathematics is to mothers. What is known is that is they are keen for their children to receive an education that provides them with opportunities for their present and future lives. However, gaining access to education is challenging given that the language of instruction in schools is written to English conventions, decontextualised and disconnected from the students’ culture, community and home language. This paper discusses some of the issues raised in the literature about what parents are confronted with when making decisions about their children’s education.

Social inequalities and parent involvement in children’s education in the early years of school

Strengthening cooperation between schools and parents is critical to improving learning outcomes for children. The chapter focuses on parental engagement in their children’s education in the early years of school. It considers issues of social and cultural capital as important to whether, or not, parents are involved in their children’s schooling. Analyses of data from a national representative sample of children and their families who participate in Growing up in Australia: The Longitudinal Study of Australian Children are presented. Results indicated that higher family socio-economic position was associated with higher levels of parental involvement and higher expectations about children’s future level of education.

Young people’s aspirations for education, work, family and leisure

Young people are arguably facing more ‘complex and contested’ transitions to adulthood and an increasing array of ‘non-linear’ paths. Education and training have been extended, identity is increasingly shaped through leisure and consumerism and youth must navigate their life trajectories in highly individualised ways. The study utilises 819 short essays compiled by students aged 14–16 years from 19 schools in Australia. It examines how young people understand their own unique positions and the possibilities open to them through their aspirations and future orientations to employment and family life. These young people do not anticipate postponing work identities, but rather embrace post-school options such as gaining qualifications, work experience and achieving financial security. Boys expected a distant involvement in family life secondary to participation in paid work. In contrast, around half the girls simultaneously expected a future involving primary care-giving and an autonomous, independent career, suggesting attempts to remake gendered inequalities

Why do family firms congregate in certain industries?

We propose that family firm involvement and performance across industries is not random and is related to specific industry conditions. Using the population of listed companies on the Taiwan Stock Exchange over the period 1997-2007 we find that family firms are more involved in industries with more fixed assets, consistent with the long-term view of family owners, and in industry conditions that make it potentially easier for family owners to consume private benefits of control. Overall, we document a positive relationship between family firm involvement and performance, which indicates a net advantage for family firm shareholders in industries where family firms congregate. However, we also find that family firm performance is negatively affected when family firms use more debt and maintain a higher control wedge than their industry counterparts.