Calcium dynamics and modulation in carrot somatic embryogenesis.

Free calcium (Ca2+) is a pivotal player in different in vivo and in vitro morphogenic processes. In the induction of somatic embryogenesis, its role has been demonstrated in different species. In carrot, however, this role has been more controversial. In this work, we developed carrot lines expressing cameleon Ca2+ sensors. With them, Ca2+ levels and distribution in the different embryogenic structures formed during the induction and development of somatic embryos were analyzed by FRET. We also used different chemicals to modulate intracellular Ca2+ levels (CaCl2, ionophore A23187, EGTA), to inhibit calmodulin (W-7) and to inhibit callose synthesis (2-deoxy-D-glucose) at different times, principally during the first stages of embryo induction. Our results showed that high Ca2+ levels and the development of a callose layer are markers of cells induced to embryogenesis, which are the precursors of somatic embryos. Disorganized calli and embryogenic masses have different Ca2+ patterns associated to their embryogenic competence, with higher levels in embryogenic cells than in callus cells. The efficiency of somatic embryogenesis in carrot can be effectively modulated by allowing, within a range, more Ca2+ to enter the cell to act as a second messenger to trigger embryogenesis induction. Once induced, Ca2+-calmodulin signaling seems related with the transcriptional remodeling needed for embryo progression, and alterations of Ca2+ or calmodulin levels negatively affect the efficiency of the process.

Kaempferol-3-rhamnoside overaccumulation in flavonoid 3'-hydroxylase tt7 mutants compromises seed coat outer integument differentiation and seed longevity.

Seeds slowly accumulate damage during storage, which ultimately results in germination failure. The seed coat protects the embryo from the external environment, and its composition is critical for seed longevity. Flavonols accumulate in the outer integument. The link between flavonol composition and outer integument development has not been explored. Genetic, molecular and ultrastructural assays on loss-of-function mutants of the flavonoid biosynthesis pathway were used to study the effect of altered flavonoid composition on seed coat development and seed longevity. Controlled deterioration assays indicate that loss of function of the flavonoid 3' hydroxylase gene TT7 dramatically affects seed longevity and seed coat development. Outer integument differentiation is compromised from 9 d after pollination in tt7 developing seeds, resulting in a defective suberin layer and incomplete degradation of seed coat starch. These distinctive phenotypes are not shared by other mutants showing abnormal flavonoid composition. Genetic analysis indicates that overaccumulation of kaempferol-3-rhamnoside is mainly responsible for the observed phenotypes. Expression profiling suggests that multiple cellular processes are altered in the tt7 mutant. Overaccumulation of kaempferol-3-rhamnoside in the seed coat compromises normal seed coat development. This observation positions TRANSPARENT TESTA 7 and the UGT78D1 glycosyltransferase, catalysing flavonol 3-O-rhamnosylation, as essential players in the modulation of seed longevity.

Comparative analysis of wild-type accessions reveals novel determinants of Arabidopsis seed longevity.

Understanding the genetic factors involved in seed longevity is of paramount importance in agricultural and ecological contexts. The polygenic nature of this trait suggests that many of them remain undiscovered. Here, we exploited the contrasting seed longevity found amongst Arabidopsis thaliana accessions to further understand this phenomenon. Concentrations of glutathione were higher in longer-lived than shorter-lived accessions, supporting that redox poise plays a prominent role in seed longevity. However, high seed permeability, normally associated with shorter longevity, is also present in long-lived accessions. Dry seed transcriptome analysis indicated that the contribution to longevity of stored messenger RNA (mRNAs) is complex, including mainly accession-specific mechanisms. The detrimental effect on longevity caused by other factors may be counterbalanced by higher levels of specific mRNAs stored in dry seeds, for instance those of heat-shock proteins. Indeed, loss-of-function mutant analysis demonstrated that heat-shock factors HSF1A and 1B contributed to longevity. Furthermore, mutants of the stress-granule zinc-finger protein TZF9 or the spliceosome subunits MOS4 or MAC3A/MAC3B, extended seed longevity, positioning RNA as a novel player in the regulation of seed viability. mRNAs of proteins with putative relevance to longevity were also abundant in shorter-lived accessions, reinforcing the idea that resistance to ageing is determined by multiple factors.

[Sexual behavior, unsafe practices and contraception in students attending Alicante University (Spain)]. / Comportamiento sexual, prácticas de riesgo y anticoncepción en jóvenes universitarios de Alicante.

OBJECTIVE: To identify sexual behavior, contraception, and unsafe practices in students attending Alicante University, as well as to explore gender differences. METHOD: We performed a cross-sectional descriptive study in Alicante University. Participants consisted of 184 students studying for a Diploma in Human Nutrition and Dietetics or for a Degree in Economics in the 2004-2005 academic year. Data on information sources, knowledge and use of family planning centers, and sexual experience were gathered using a self-administered anonymous and confidential questionnaire. RESULTS: The mean age was 21.6 years and 140 participants were women. Information sources on sexuality and contraception were related to the students' social and educational environment. The age of beginning coital sexual relations was 17.8 years. The most frequent sexual practices were vaginal coitus and oral sex. Nearly 30% of the students (n = 51) used the postcoital pill. Men started sexual relations earlier and had a greater number of partners than women. The percentage of women who needed to be in love to maintain sexual relations was higher than that in men. A greater percentage of men had had sexual relations under the effect of drugs. CONCLUSIONS: There is a need to improve awareness of responsible sex in the university setting. The gender differences associated with risk behaviors and the use of contraceptive methods, which influence the prevention of sexually transmitted diseases and unwanted pregnancies, should be taken into account.

Comportamiento sexual, prácticas de riesgo y anticoncepción en jóvenes universitarios de Alicante / Sexual behavior, unsafe practices and contracepction in students attending Alicante University (Spain)

Objetivo. Identificar la conducta sexual, de anticoncepción y prácticas de riesgo en jóvenes universitarios de Alicante, así como explorar diferencias de sexo. Método. Estudio descriptivo y transversal realizado en la Universidad de Alicante. Los participantes fueron 184 alumnos que cursaban sus estudios de la diplomatura de Nutrición Humana y Dietética, y de la licenciatura de Económicas en el curso 2004-2005. Mediante cuestionario autoadministrado de carácter anónimo y confidencial, se obtuvo información relativa a las fuentes de información, conocimiento y uso de los centros de planificación familiar y experiencia sobre relaciones sexuales. Resultados. La edad media fue de 21,6 años, y 140 eran mujeres. Las fuentes de información acerca de sexualidad y anticoncepción estaban relacionadas con su entorno social y educativo. La edad de inicio de las relaciones sexuales coitales fue de 17,8 años. Las prácticas sexuales más frecuentes fueron el coito vaginal y el sexo oral. Cerca del 30% (51) utilizó la píldora poscoital. Los varones habían iniciado antes la relación sexual y habían tenido mayor número de parejas que las mujeres. El porcentaje de mujeres que habían necesitado estar enamoradas para mantener relaciones sexuales fue mayor que en los varones. Los varones habían mantenido relaciones sexuales bajo el efecto de drogas en mayor porcentaje que las mujeres. Conclusiones. Dentro del contexto universitario se deben continuar las actividades formativas hacia una sexualidad responsable, teniendo en cuenta las diferencias de sexo que pueden asociarse a conductas de riesgo e incidiendo en el uso de los métodos anticonceptivos y su relación con la prevención de las enfermedades de transmisión sexual y embarazos no deseados

Objective. To identify sexual behavior, contraception, and unsafe practices in students attending Alicante University, as well as to explore gender differences. Method. We performed a cross-sectional descriptive study in Alicante University. Participants consisted of 184 students studying for a Diploma in Human Nutrition and Dietetics or for a Degree in Economics in the 2004-2005 academic year. Data on information sources, knowledge and use of family planning centers, and sexual experience were gathered using a self-administered anonymous and confidential questionnaire. Results. The mean age was 21.6 years and 140 participants were women. Information sources on sexuality and contraception were related to the students' social and educational environment. The age of beginning coital sexual relations was 17.8 years. The most frequent sexual practices were vaginal coitus and oral sex. Nearly 30% of the students (n = 51) used the postcoital pill. Men started sexual relations earlier and had a greater number of partners than women. The percentage of women who needed to be in love to maintain sexual relations was higher than that in men. A greater percentage of men had had sexual relations under the effect of drugs. Conclusions. There is a need to improve awareness of responsible sex in the university setting. The gender differences associated with risk behaviors and the use of contraceptive methods, which influence the prevention of sexually transmitted diseases and unwanted pregnancies, should be taken into account