Micropropagação de singônio.

A propagação vegetativa de Syngonium podophyllum Schott (Araceae) em campo torna-se difícil para os produtores que buscam obter mudas de qualidade e em larga escala, em vista de problemas fitossanitários. Utilizaram-se gemas laterais da axila foliar de S. podophyllum para micropropagar essa espécie ornamental e, na fase de estabelecimento, submeteram-se os explantes a dois procedimentos de desinfestação: o primeiro consistiu em uma préassepsia em bancada de laboratório, com imersão das gemas em hipoclorito de sódio a 1%, durante 15 minutos, e de uma assepsia em câmara de fluxo laminar, com imersão em etanol 70% e em hipoclorito de sódio a 1%, por 3 e 30 minutos respectivamente; o segundo procedimento consistiu na assepsia apenas em câmara de fluxo laminar. Os explantes foram inoculados em meio MS e MS adicionado de ácido 3-indolacético (AIA) e 6-benzilaminopurina (BAP), ambos a 1,0 mg.L-1. Na fase de proliferação, submeteram-se os explantes a concentrações de 1,0; 2,5 e 4,0 mg.L-1 de BAP, adicionadas ao meio MS, ransferindo-se os brotos obtidos para frascos com meio MS para o crescimento e desenvolvimento de plântulas. A exposição das gemas laterais axilares a uma pré-assepsia em bancada e posterior assepsia em câmara de fluxo laminar foi mais eficiente na desinfestação dos explantes, com 100 % de sobrevivência. A adição dos reguladores de crescimento, AIA e BAP, ambos a 1,0 mg.L-1, no meio MS, promoveu maior desenvolvimento das plântulas durante o estabelecimento in vitro da cultura. Concentrações elevadas de BAP no meio de proliferação não induziram um aumento significativo no número médio de brotos por explante; entretanto, resultaram numa redução significativa do número médio de folhas e raízes. Os explantes provenientes dos subcultivos de proliferação do tratamento com 1,0 mg.L-1 de BAP, quando cultivados em meio MS, isento de reguladores de crescimento, apresentaram maior esenvolvimento de plântulas

Palm seed and fruit lipid composition : phylogenetic and ecological perspectives

Background and aims - Palms are vital to worldwide human nutrition, in particular as major sources of vege-table oils. However, our knowledge of seed and fruit lipid diversity in the family Arecaceae is limited. We therefore aimed to explore relationships between seed and fruit lipid content, fatty acid composition in the respective tissues, phylogenetic factors and biogeographical parameters.Methods - Oil content and fatty acid composition were characterized in seeds and fruits of 174 and 144 palmspecies respectively. Distribution, linear regression and multivariate analyses allowed an evaluation of the chemotaxonomic value of these traits and their potential relationship with ecological factors.Key Results - A considerable intra-family diversity for lipid traits was revealed. Species with the most lipid-richseeds belonged to the tribe Cocoseae, while species accumulating oil in the mesocarp occurred in all subfamilies and two-thirds of the tribes studied. Seed and fruit lipid contents were not correlated. Fatty acid composition of mesocarp oil was highly variable within tribes. By contrast, within-tribe diversity for seed lipid traits was low, whereas between-tribe variability was high. Consequently, multivariate analyses of seed lipid traits produced groupings of species belonging to the same tribe. Medium-chain fatty acids predominated in seeds of most palm species, but they were also accumulated in the mesocarp in some cases. Seed unsaturated fatty acid content correl-ated with temperature at the coldest latitude of natural occurrence.Conclusion - Several previously uncharacterized palms were identified as potential new sources of vegetable oils for comestible or non-food use. Seed lipid traits reflect genetic drift that occurred during the radiation of the family and therefore are highly relevant to palm chemotaxonomy. Our data also suggest that seed unsaturated fatty acids may provide an adaptive advantage in the coldest environments colonized by palms by maintaining storage lipids in liquid form for efficient mobilization during germination

Integrative analysis of the late maturation programme and desiccation tolerance mechanisms in intermediate coffee seeds.

The intermediate seed category was defined in the early 1990s using coffee (Coffea arabica) as a model. In contrast to orthodox seeds, intermediate seeds cannot survive complete drying, which is a major constraint for seed storage, for both biodiversity conservation and agricultural purposes. However, intermediate seeds are considerably more tolerant to drying than recalcitrant seeds, which are highly sensitive to desiccation. To gain insight into the mechanisms governing such differences, changes in desiccation tolerance (DT), hormone content and the transcriptome were analysed in developing coffee seeds. Acquisition of DT coincided with a dramatic transcriptional switch characterised by the repression of primary metabolism, photosynthesis and respiration, and the upregulation of genes coding for late embryogenesis abundant (LEA) proteins, heat shock proteins (HSP) and antioxidant enzymes. Analysis of heat-stable proteome in the mature coffee seed confirmed the accumulation of LEA proteins identified at the transcript level. Transcriptome analysis also suggests a major role for ABA and for the transcription factors CaHSFA9, CaDREB2G, CaANAC029, CaPLATZ and CaDOG-like in DT acquisition. The ability of CaHSFA9 and CaDREB2G to trigger HSP gene transcription was validated by Agrobacterium-mediated transformation of coffee somatic embryos

Seed comparative genomics in three coffee species identify desiccation tolerance mechanisms in intermediate seeds

International audienceIn contrast to desiccation-tolerant 'orthodox' seeds, so-called 'intermediate' seeds cannot survive complete drying and are short-lived. All species of the genus Coffea produce intermediate seeds, but they show a considerable variability in seed desiccation tolerance (DT), which may help to decipher the molecular basis of seed DT in plants. We performed a comparative transcriptome analysis of developing seeds in three coffee species with contrasting desiccation tolerance. Seeds of all species shared a major transcriptional switch during late maturation that governs a general slowdown of metabolism. However, numerous key stress-related genes, including those coding for the late embryogenesis abundant protein EM6 and the osmosensitive calcium channel ERD4, were up-regulated during DT acquisition in the two species with high seed DT, C. arabica and C. eugenioides. By contrast, we detected up-regulation of numerous genes involved in the metabolism, transport, and perception of auxin in C. canephora seeds with low DT. Moreover, species with high DT showed a stronger down-regulation of the mitochondrial machinery dedicated to the tricarboxylic acid cycle and oxidative phosphorylation. Accordingly, respiration measurements during seed dehydration demonstrated that intermediate seeds with the highest DT are better prepared to cease respiration and avoid oxidative stresses