Simple and efficient methods to generate split roots and grafted plants useful for long-distance signaling studies in Medicago truncatula and other small plants

BACKGROUND: Long distance signaling is a common phenomenon in animal and plant development. In plants, lateral organs such as nodules and lateral roots are developmentally regulated by root-to-shoot and shoot-to-root long distance signaling. Grafting and split root experiments have been used in the past to study the systemic long distance effect of endogenous and environmental factors, however the potential of these techniques has not been fully realized because data replicates are often limited due to cumbersome and difficult approaches and many plant species with soft tissue are difficult to work with. Hence, developing simple and efficient methods for grafting and split root inoculation in these plants is of great importance. RESULTS: We report a split root inoculation system for the small legume M. truncatula as well as robust and reliable techniques of inverted-Y grafting and reciprocal grafting. Although the split root technique has been historically used for a variety of experimental purposes, we made it simple, efficient and reproducible for M. truncatula. Using our split root experiments, we showed the systemic long distance suppression of nodulation on a second wild type root inoculated after a delay, as well as the lack of this suppression in mutants defective in autoregulation. We demonstrated inverted-Y grafting as a method to generate plants having two different root genotypes. We confirmed that our grafting method does not affect the normal growth and development of the inserted root; the composite plants maintained normal root morphology and anatomy. Shoot-to-root reciprocal grafts were efficiently made with a modification of this technique and, like standard grafts, demonstrate that the regulatory signal defective in rdn1 mutants acts in the root. CONCLUSIONS: Our split root inoculation protocol shows marked improvement over existing methods in the number and quality of the roots produced. The dual functions of the inverted-Y grafting approach are demonstrated: it is a useful system to produce a plant having roots of two different genotypes and is also more efficient than published shoot-to-root reciprocal grafting techniques. Both techniques together allow dissection of long distance plant developmental regulation with very simple, efficient and reproducible approaches

Phylogenetic Distribution of Intron Positions in Alpha-Amylase Genes of Bilateria Suggests Numerous Gains and Losses

Most eukaryotes have at least some genes interrupted by introns. While it is well accepted that introns were already present at moderate density in the last eukaryote common ancestor, the conspicuous diversity of intron density among genomes suggests a complex evolutionary history, with marked differences between phyla. The question of the rates of intron gains and loss in the course of evolution and factors influencing them remains controversial. We have investigated a single gene family, alpha-amylase, in 55 species covering a variety of animal phyla. Comparison of intron positions across phyla suggests a complex history, with a likely ancestral intronless gene undergoing frequent intron loss and gain, leading to extant intron/exon structures that are highly variable, even among species from the same phylum. Because introns are known to play no regulatory role in this gene and there is no alternative splicing, the structural differences may be interpreted more easily: intron positions, sizes, losses or gains may be more likely related to factors linked to splicing mechanisms and requirements, and to recognition of introns and exons, or to more extrinsic factors, such as life cycle and population size. We have shown that intron losses outnumbered gains in recent periods, but that “resets” of intron positions occurred at the origin of several phyla, including vertebrates. Rates of gain and loss appear to be positively correlated. No phase preference was found. We also found evidence for parallel gains and for intron sliding. Presence of introns at given positions was correlated to a strong protosplice consensus sequence AG/G, which was much weaker in the absence of intron. In contrast, recent intron insertions were not associated with a specific sequence. In animal Amy genes, population size and generation time seem to have played only minor roles in shaping gene structures

Elderly widows' experience of sexuality and their perceptions regarding the family's opinion

O objetivo deste trabalho foi descrever a vivência da sexualidade por mulheres idosas viúvas, frequentadoras de um Centro de Convivência do Idoso, e verificar a percepção quanto à opinião dos seus familiares. Tratou-se de uma pesquisa qualitativa e exploratório-descritiva. Os dados foram coletados por meio de entrevistas semiestruturadas e submetidos à análise de conteúdo temática. Emergiram desta as categorias: 1) a vivência da sexualidade sofreu algumas modificações após o estado de viuvez garantindo submissão às normas e regras sociais para o comportamento feminino; 2) as idosas assumem ter optado pela vida sem um novo companheiro; 3) a família apoia o convívio social, mas não existe declaração de apoio para novos relacionamentos amorosos; e 4) houve ressignificação das questões de gênero no tocante às mudanças relativas ao papel social da mulher, depois da viuvez. Concluímos, portanto, que essas mulheres não vivem, de forma plena e livre, sua sexualidade, pois se submetem às normas sociais.The aim of this study was to describe the experience of sexuality of elderly widows attending an Elderly Community Centre and to verify their perceptions regarding their relatives' opinion. This was a qualitative and descriptive-exploratory research. Data were collected through semi-structured interviews and submitted to a thematic content analysis. The following categories emerged: 1) the experience of sexuality was modified after the women became widows, so that the female behavior complies with social norms and rules; 2) the elderly widows assume they have opted for life without a new partner; 3) the family supports social interaction, but there is no statement of support for new loving relationships; and 4) gender issues were redefined in relation to changes in the social role of women after widowhood. We conclude, therefore, that these women do not experience, neither fully nor freely, their sexuality, because they submit to the social norms