BackgroundRoot-knot nematodes (RKN– Meloidogyne genus) present extensive challenges to soybean crop. The soybean line (PI 595099) is known to be resistant against specific strains and races of nematode species, thus its differential gene expression analysis can lead to a comprehensive gene expression profiling in the incompatible soybean-RKN interaction. Even though many disease resistance genes have been studied, little has been reported about phytohormone crosstalk on modulation of ROS signaling during soybean-RKN interaction.ResultsUsing 454 technology to explore the common aspects of resistance reaction during both parasitism and resistance phases it was verified that hormone, carbohydrate metabolism and stress related genes were consistently expressed at high levels in infected roots as compared to mock control. Most noteworthy genes include those encoding glycosyltransferases, peroxidases, auxin-responsive proteins and gibberellin-regulated genes. Our data analysis suggests the key role of glycosyltransferases, auxins and components of gibberellin signal transduction, biosynthesis and deactivation pathways in the resistance reaction and their participation in jasmonate signaling and redox homeostasis in mediating aspects of plant growth and responses to biotic stress.ConclusionsBased on this study we suggest a reasonable model regarding to the complex mechanisms of crosstalk between plant hormones, mainly gibberellins and auxins, which can be crucial to modulate the levels of ROS in the resistance reaction to nematode invasion. The model also includes recent findings concerning to the participation of DELLA-like proteins and ROS signaling controlling plant immune or stress responses. Furthermore, this study provides a dataset of potential candidate genes involved in both nematode parasitism and resistance, which can be tested further for their role in this biological process using functional genomics approaches.

Soybean is an important crop for Brazilian agribusiness. However, many factors can limit its production, especially root-knot nematode infection. Studies on the mechanisms employed by the resistant soybean genotypes to prevent infection by these nematodes are of great interest for breeders. For these reasons, the aim of this work is to characterize the transcriptome of soybean line PI 595099-Meloidogyne javanica interaction through expression analysis. Two cDNA libraries were obtained using a pool of RNA from PI 595099 uninfected and M. javanica (J2) infected roots, collected at 6, 12, 24, 48, 96, 144 and 192 h after inoculation. Around 800 ESTs (Expressed Sequence Tags) were sequenced and clustered into 195 clusters. In silico subtraction analysis identified eleven differentially expressed genes encoding putative proteins sharing amino acid sequence similarities by using BlastX: metallothionein, SLAH4 (SLAC1 Homologue 4), SLAH1 (SLAC1 Homologue 1), zinc-finger proteins, AN1-type proteins, auxin-repressed proteins, thioredoxin and nuclear transport factor 2 (NTF-2). Other genes were also found exclusively in nematode stressed soybean roots, such as NAC domain-containing proteins, MADS-box proteins, SOC1 (suppressor of overexpression of constans 1) proteins, thioredoxin-like protein 4-Coumarate-CoA ligase and the transcription factor (TF) MYBZ2. Among the genes identified in non-stressed roots only were Ser/Thr protein kinases, wound-induced basic protein, ethylene-responsive family protein, metallothionein-like protein cysteine proteinase inhibitor (cystatin) and Putative Kunitz trypsin protease inhibitor. An understanding of the roles of these differentially expressed genes will provide insights into the resistance mechanisms and candidate genes involved in soybean-M. javanica interaction and contribute to more effective control of this pathogen.

RESUMO-Este trabalho teve por objetivo estudar, sob encharcamento contínuo, mecanismos bioquímicos, como concentração de proteína total, oxidação protéica e peroxidação de lipídeos de membrana, em folha e em raiz de plântulas, nos estádios V3-V5, da variedade de milho BRS 4154 (Saracura) após o primeiro (C1), oitavo (C8) e décimo sexto (C16) ciclos de seleção sob encharcamento intermitente, tendo como testemunha a variedade BR 107. Sementes dos ciclos de seleção do Saracura, C1, C8 e C16 e da testemunha, BR 107, foram plantadas com o embrião voltado para cima, a uma profundidade aproximada de 1 cm da superfície do solo, em copos de plástico de 200 ml, perfurados na base e preenchidos com solo de várzea. Os tratamentos constituíram-se de diferentes períodos de encharcamento: 0 h (sem encharcamento) e 8, 24, 48, 72, 96, 120 e 144 h sob encharcamento contínuo, utilizando-se água destilada até a superfície do solo. Os resultados do teor e oxidação protéicos, da peroxidação lipídica radicular e foliar foram responsivos ao encharcamento e mostraram adaptações das plântulas de milho ao estresse prolongado, obtendo-se, de maneira geral, a mesma tendência em todos os genótipos.

Resumo -O objetivo deste trabalho foi determinar os tipos principais de ações gênicas responsáveis pela expressão fenotípica de alguns caracteres de qualidade da vagem, em cruzamento de feijão-vagem e feijão-comum. Foram avaliadas duas populações segregantes (F 2 e F 2:3 ), além das linhagens parentais. Como genitora feminina, utilizou-se a cultivar de feijão-vagem Conquista Rasteiro e, como genitora masculina, a linhagem de feijão-comum H126. Foram avaliados: comprimento da vagem, largura entre as suturas, largura das valvas, formato da vagem e teor de fibra da vagem . Os efeitos não-aditivos destacaram-se em todas as características avaliadas. Embora tenha ocorrido predominância dos efeitos genéticos sobre os ambientais, nas características comprimento e formato da vagem e teor de fibra, a eficiência da seleção em plantas individuais tendeu a ser bastante baixa nas gerações segregantes pouco avançadas, em razão dos baixos valores da herdabilidade no sentido restrito, exceto para formato da vagem. O predomínio dos efeitos genéticos sobre os ambientais em todas as características em nível de família, associado a valores de herdabilidade no sentido restrito em famílias F 2:3 , indica a alta eficiência para a seleção de famílias nas gerações segregantes pouco avançadas, com relação a todas as características, exceto para comprimento e teor de fibra.Termos para indexação: Phaseolus vulgaris, ação gênica, herdabilidade, populações segregantes. Genetic control of pod quality in a cross between snap beans and common beanAbstract -The objective of this work was to study the main gene actions involved in phenotypic expression of pod quality in a cross between snap beans and common bean. Two segregating populations (F 2 and F 2:3 ) and the parental lines were evaluated. The snap bean cultivar Conquista Rasteiro was used as the female parent, and the common bean line H126 as the male parent. Pod length, between-suture width, valve width, pod shape, and percentage of pod fiber were evaluated. Non-additive gene effects were important for all traits evaluated. Even though genetic effects were higher than the environmental ones for pod length, pod shape, and percentage of pod fiber, efficiency of selection in individual plants tended to be low in early segregating generations, as demonstrated by the low narrow-sense heritabilities for most traits, except for pod shape. At family level, genetic effects were higher than the environmental ones for all evaluated traits, and most traits presented high narrowsense heritabilities, indicating high selection efficiency at family level in early segregating generations for all traits, except for pod length and percentage of fiber.Index terms: Phaseolus vulgaris, gene action, heritability, segregating populations. IntroduçãoO feijão-vagem pertence à mesma espécie do feijão-comum (Phaseolus vulgaris L.), e é uma das dez hortaliças mais cultivadas no Brasil, produzida, principalmente, por agricultores familiares (Peixoto et al., 2001).Grande parte das características que distinguem o feijã...