Rare instances of haploid inducer DNA in potato dihaploids and ploidy-dependent genome instability.

In cultivated tetraploid potato (Solanum tuberosum), reduction to diploidy (dihaploidy) allows for hybridization to diploids and introgression breeding and may facilitate the production of inbreds. Pollination with haploid inducers (HIs) yields maternal dihaploids, as well as triploid and tetraploid hybrids. Dihaploids may result from parthenogenesis, entailing the development of embryos from unfertilized eggs, or genome elimination, entailing missegregation and the loss of paternal chromosomes. A sign of genome elimination is the occasional persistence of HI DNA in some dihaploids. We characterized the genomes of 919 putative dihaploids and 134 hybrids produced by pollinating tetraploid clones with three HIs: IVP35, IVP101, and PL-4. Whole-chromosome or segmental aneuploidy was observed in 76 dihaploids, with karyotypes ranging from 2n = 2x - 1 = 23 to 2n = 2x + 3 = 27. Of the additional chromosomes in 74 aneuploids, 66 were from the non-inducer parent and 8 from the inducer parent. Overall, we detected full or partial chromosomes from the HI parent in 0.87% of the dihaploids, irrespective of parental genotypes. Chromosomal breaks commonly affected the paternal genome in the dihaploid and tetraploid progeny, but not in the triploid progeny, correlating instability to sperm ploidy and to haploid induction. The residual HI DNA discovered in the progeny is consistent with genome elimination as the mechanism of haploid induction.

Los antioxidantes en la encrucijada: mitos y realidades / Os antioxidantes na encruzilhada: mitos e realidades / Antioxidants at the crossroads; myths and realities

El equilibrio entre generación y eliminación de especies reactivas de oxígeno y nitrógeno es necesario para mantener las funciones fisiológicas del organismo. Para ello se dispone de un sistema de defensa cuya función es la de eliminar las especies reactivas de oxígeno y nitrógeno, manteniendo así la homeostasis redox. Este sistema incluye componentes enzimáticos y no enzimáticos. El aumento significativo de las especies reactivas producidas por el desequilibrio entre formación y eliminación genera estrés oxidativo, lo que puede dar lugar a pérdida de integridad celular y función enzimática, e inestabilidad genómica. Este daño oxidativo estaría involucrado en el envejecimiento y en enfermedades degenerativas. Para evitar estrés oxidativo y el daño producido, se propone la ingestión de compuestos antioxidantes, bien sean fitofármacos o suplementos alimenticios. Estos compuestos pueden actuar suprimiendo la formación o atrapando las especies reactivas, o bien aumentando o protegiendo el sistema de defensa antioxidante. La popularidad de las sustancias antioxidantes ha llevado al uso indebido y al abuso de las mismas, apoyándose en estudios in vitro y extrapolando erróneamente los resultados a una posible eficacia in vivo . La presente revisión destaca los mitos y realidades en el mundo de los antioxidantes, desvelando algunos aspectos desconocidos y la parte negativa del uso y abuso. Como ejemplos mal utilizados en este aspecto destacan las vitaminas A, C y E, fitoestrógenos, melatonina y resveratrol. Como conclusión final se establece que los antioxidantes son necesarios para la vida, pero su empleo como complemento o suplemento será de especial interés solo cuando exista una carencia o alteración fisiopatológica que así lo recomiende (AU)

The balance between the generation and deletion of reactive oxygen and nitrogen species is necessary for maintaining the physiological functions in the organism. For this purpose, the organism has an antioxidant defense system, which eliminates these reactive species, maintaining the redox homeostasis. This system includes enzymatic and non-enzymatic components. The significant increase in reactive species produced by the imbalance between generation and elimination generates oxidative stress. This situation may produce loss of cellular integrity and enzymatic function, as well as genomic instability. The oxidative damage would be involved in aging and degenerative diseases. To prevent the oxidative effects and damage, the intake of antioxidants such as herbal medicinal products or dietary supplement is proposed. These compounds may act by suppressing the formation or scavenging the reactive species, as well as increasing or protecting the physiological antioxidant defense system. The popularity of antioxidants has led to the misuse and abuse of them, based on n vitro studies. The results obtained have been erroneously extrapolated to a possible efficacy in vivo . This review highlights the myths and realities about the antioxidants, unveiling some unknown and negative aspects of their use and abuse. Examples of misuse in this aspect include vitamins A, C and E, phytoestrogens, resveratrol and melatonin. In summary, the antioxidants are necessary for life, but its use as a complement or supplement will be of special interest when there is a lack of them, or when in a pathophysiological alteration will be recommended (AU)

O equilíbrio entre a formação e a eliminação de espécies reactivas de oxigénio e azoto é necessário para manter as funções fisiológicas no organismo. Para isso o organismo possui um sistema de defesa antioxidante, que elimina estas espécies reactivas, mantendo assim a homeostase redox. Este sistema inclui componentes enzimáticos e não enzimáticos. O aumento significativo de espécies reactivas produzidas pelo desequilíbrio entre a produção e a eliminação gera o stress oxidativo. Esta situação pode produzir a perda de integridade celular e função enzimática, bem como a instabilidade genómica. Este dano oxidativo poderá estar envolvido no processo de envelhecimento e nas doenças degenerativas. Para prevenir os efeitos oxidantes e os danos produzidos, é proposta a ingestão de antioxidantes, seja como medicamentos à base de plantas ou como suplementos alimentares. Estes compostos podem actuar por suprimir a formação ou por reagirem com as espécies reactivas, bem como aumentando ou protegendo o sistema de defesa antioxidante fisiológico. Com base em estudos in vitro e extrapolando erradamente os resultados para uma possível eficácia in vivo tem-se fomentado a utilização indevida e abuso do consumo de antioxidantes. Esta revisão destaca os mitos e realidades sobre os an-tioxidantes, revelando alguns aspectos desconhecidos e negativos de seu uso e abuso. Como exemplos de mau uso neste aspecto destacam-se as vitaminas A, C e E, fitoestrógenios, resveratrol e melatonina. Em resumo, os antioxidantes são necessários para a vida, mas a sua utilização como um complemento ou suplemento terá interesse especial apenas quando existe uma carência ou alteração fisiopatológica que assim o recomende

Low intake of calcium, folate, nicotinic acid, vitamin E, retinol, beta-carotene and high intake of pantothenic acid, biotin and riboflavin are significantly associated with increased genome instability--results from a dietary intake and micronucleus index survey in South Australia.

The aim of this study was to determine the association between dietary intake, determined using a food frequency questionnaire, and genome damage in lymphocytes measured using the micronucleus (MN) assay. The study, performed on 190 healthy individuals (mean age 47.8 years, 46% males), also examined whether a supplementation with beta-carotene, vitamins C and E along with zinc (ACEZn), in a randomized trial for 6 months, improves genome stability. Multivariate analysis of baseline data showed that (1) the highest tertile of intake of vitamin E, retinol, folic acid, nicotinic acid (preformed) and calcium is associated with significant reductions in MN frequency, i.e. -28, -31, -33, -46 and -49%, respectively (P < 0.005) relative to the lowest tertile of intake and (2) the highest tertile of intake of riboflavin, pantothenic acid and biotin was associated with significant increases in MN frequency, i.e. +36% (P = 0.054), +51% (P = 0.021), and +65% (P = 0.001), respectively, relative to the lowest tertile of intake. Mid-tertile beta-carotene intake was associated with an 18% reduction in MN frequency (P = 0.038); however, the highest tertile of intake (>6400 microg/day) resulted in an 18% increment in MN frequency. Supplementation with ACEZn significantly reduced the MN index by 13% (P = 0.038). The study also showed interactive additive effects such as the protective effect of increased calcium intake (-46%) and the exacerbating effect of riboflavin (+42%) on increased genome damage caused by low folate intake. The results from this study illustrate the strong impact of a wide variety of micronutrients and their interactions on genome health, depending on the level of intake.