Homoeolog expression bias and expression level dominance (ELD) in four tissues of natural allotetraploid Brassica napus.

BACKGROUND: Allopolyploidy is widespread in angiosperms, and they can coordinate two or more different genomes through genetic and epigenetic modifications to exhibit stronger vigor and adaptability. To explore the changes in homologous gene expression patterns in the natural allotetraploid Brassica napus (AnAnCnCn) relative to its two diploid progenitors, B. rapa (ArAr) and B. oleracea (CoCo), after approximately 7500 years of domestication, the global gene pair expression patterns in four major tissues (stems, leaves, flowers and siliques) of these three species were analyzed using an RNA sequencing approach. RESULTS: The results showed that the 'transcriptomic shock' phenomenon was alleviated in natural B. napus after approximately 7500 years of natural domestication, and most differentially expressed genes (DEGs) in B. napus were downregulated relative to those in its two diploid progenitors. The KEGG analysis indicated that three pathways related to photosynthesis were enriched in both comparison groups (AnAnCnCn vs ArAr and AnAnCnCn vs CoCo), and these pathways were all downregulated in four tissues of B. napus. In addition, homoeolog expression bias and expression level dominance (ELD) in B. napus were thoroughly studied through analysis of expression levels of 27,609 B. rapa-B. oleracea orthologous gene pairs. The overwhelming majority of gene pairs (an average of 86.7%) in B. napus maintained their expression pattern in two diploid progenitors, and approximately 78.1% of the gene pairs showed expression bias with a preference toward the A subgenome. Overall, an average of 48, 29.7 and 22.3% homologous gene pairs exhibited additive expression, ELD and transgressive expression in B. napus, respectively. The ELD bias varies from tissue to tissue; specifically, more gene pairs in stems and siliques showed ELD-A, whereas the opposite was observed in leaves and flowers. More transgressive upregulation, rather than downregulation, was observed in gene pairs of B. napus. CONCLUSIONS: In general, these results may provide a comprehensive understanding of the changes in homologous gene expression patterns in natural B. napus after approximately 7500 years of evolution and domestication and may enhance our understanding of allopolyploidy.

Relações fisiológicas em mudas de pata-de-vaca (Bauhinia forficata Link) / Physiologic relationships in Brazilian Orchid Tree (Bauhinia forficata Link) seedlings

Os fatores ambientais, tais como: temperatura do ar, umidade relativa do ar e radiação solar, influenciam no comportamento fisiológico dos vegetais refletindo no seu crescimento e desenvolvimento. O objetivo do trabalho foi avaliar o comportamento fisiológico em mudas de pata-de-vaca ao longo do dia e constatar qual o melhor horário para a realização de determinações de trocas gasosas. Para tanto, foram realizadas avaliações de temperatura da folha, radiação fotossinteticamente ativa, resistência estomática e transpiração, utilizando-se um porômetro, das 8:00 às 17:00 horas, em intervalos de uma hora entre as medidas. A espécie apresenta oscilações no seu mecanismo fisiológico em função do horário de avaliação e das condições climáticas, sendo o intervalo mais indicado para a realização de determinações das trocas gasosas das 10:00 às 13:00 horas.

Environmental elements, such as air temperature, relative humidity and solar radiation, affect the physiological behavior of plants, which is reflected in their growth and development. The objective of this study was to evaluate the physiological changes of Brazilian Orchid Tree seedlings over a typical day and find the best time to carry out determinations of gas exchanges. For this end, we evaluated temperature of the leaf, photosynthetically active radiation, stomatal resistance and perspiration, using a porometer, from 8:00 a.m. to 05:00 p.m., in intervals of one hour between measurements. The species presents oscillations in its physiologic mechanism in function of the time of evaluation and climatic conditions, being the most suitable interval to determine gas exchanges from 10:00 a.m. to 01:00 p.m.

Composição florística dos afloramentos rochosos do Morro do Forno, Altinópolis, São Paulo / Floristic composition of the rock outcrops of the Morro do Forno, Altinópolis-SP

Áreas de afloramentos rochosos em topos de morros abrigam uma vegetação bastante peculiar. Muitas das espécies que ocorrem nessas áreas apresentam uma série de características que permitem sua sobrevivência num ambiente com solo pobre e arenoso, com alta insolação e grande oscilação de temperatura entre o dia e a noite. Essas características particulares despertaram o interesse no estudo da flora das áreas de afloramentos rochosos do Morro do Forno (Altinópolis-SP). A flora apresenta um total de 157 espécies distribuídas em 48 famílias. Fabaceae (14 spp.), Asteraceae (12 spp.), Poaceae (12 spp.), Rubiaceae (11 spp.), Malpighiaceae (9 spp.) e Melastomataceae (8 spp.) são as famílias com o maior número de espécies. O estrato herbáceo-arbustivo caracteriza a área (61 por cento), seguido pelo arbóreo (19 por cento), sendo de menor representatividade as lianas (11 por cento) e os subarbustos (9 por cento). Muitas das espécies que ocorrem na área estão presentes em outros afloramentos rochosos brasileiros como, por exemplo, nos campos rupestres da Serra do Cipó e Serra da Canastra em Minas Gerais e nos cerrados rupestres da Chapada dos Guimarães no Mato Grosso.

Rock outcrops on the plateaus of hills have peculiar vegetation. The major part of the species occurring on these areas have various features that allow their survival under adverse environmental conditions as poor and sandy soil with intense solar radiation and great temperature ranging from day and night. These particular characteristics aroused the interest in the study of the flora on rock outcrops of Morro do Forno (Altinópolis-SP). A list of 157 species of 48 families was recorded. Fabaceae (14 spp.), Asteraceae (12 spp.), Poaceae (12 spp.), Rubiaceae (11 spp.), Malpighiaceae (9 spp.) and Melastomataceae (8 spp.) are the families with more number of species. The herbaceous-shruby stratum characterizes the area (61 percent), followed by arboreous (19 percent); lianas (11 percent) and subshruby (9 percent) are less representative. Many of the species occurring on the area are present another Brazilian rocky outcrops as, for example, the "campos rupestres" of the Minas Gerais state (Serra do Cipó and Serra da Canastra) and the "cerrados rupestres" of the Mato Grosso state (Chapada dos Guimarães).