Coffee leaf rust caused by the fungus Hemileia vastatrix is one of the most important leaf diseases of coffee plantations worldwide. Current knowledge of the H . vastatrix genome is limited and only a small fraction of the total fungal secretome has been identified. In order to obtain a more comprehensive understanding of its secretome, we aimed to sequence and assemble the entire H . vastatrix genome using two next-generation sequencing platforms and a hybrid assembly strategy. This resulted in a 547 Mb genome of H . vastatrix race XXXIII (Hv33), with 13,364 predicted genes that encode 13,034 putative proteins with transcriptomic support. Based on this proteome, 615 proteins contain putative secretion peptides, and lack transmembrane domains. From this putative secretome, 111 proteins were identified as candidate effectors (EHv33) unique to H . vastatrix , and a subset consisting of 17 EHv33 genes was selected for a temporal gene expression analysis during infection. Five genes were significantly induced early during an incompatible interaction, indicating their potential role as pre-haustorial effectors possibly recognized by the resistant coffee genotype. Another nine genes were significantly induced after haustorium formation in the compatible interaction. Overall, we suggest that this fungus is able to selectively mount its survival strategy with effectors that depend on the host genotype involved in the infection process.

Raffinose family oligosaccharides (RFOs) are implicated in plant regulatory mechanisms of abiotic stresses tolerance and, despite their antinutritional proprieties in grain legumes, little information is available about the enzymes involved in RFO metabolism in Fabaceae species. In the present study, the systematic survey of legume proteins belonging to five key enzymes involved in the metabolism of RFOs (galactinol synthase, raffinose synthase, stachyose synthase, alpha-galactosidase, and beta-fructofuranosidase) identified 28 coding-genes in Arachis duranensis and 31 in A. ipaënsis. Their phylogenetic relationships, gene structures, protein domains, and chromosome distribution patterns were also determined. Based on the expression profiling of these genes under water deficit treatments, a galactinol synthase candidate gene (AdGolS3) was identified in A. duranensis. Transgenic Arabidopsis plants overexpressing AdGolS3 exhibited increased levels of raffinose and reduced stress symptoms under drought, osmotic, and salt stresses. Metabolite and expression profiling suggested that AdGolS3 overexpression was associated with fewer metabolic perturbations under drought stress, together with better protection against oxidative damage. Overall, this study enabled the identification of a promising GolS candidate gene for metabolic engineering of sugars to improve abiotic stress tolerance in crops, whilst also contributing to the understanding of RFO metabolism in legume species.

The aim of the present study was to find out the effect of calcium on flooded maize seedlings by anatomical and ultra‐structural analyses and by measuring the enzyme activity and gene expression of polygalacturonase (PG) and superoxide dismutase (SOD). For this, maize seeds were placed to germinate in germination paper saturated with CaCl2 0.75 %. Then, 4‐day‐old seedlings were subjected to flooding in the presence or absence of CaCl2. Mesocotyl sections were sampled daily for the anatomical and ultra‐structural analyses, RT‐qPCR and activity of SOD and PG. The results showed that the presence of calcium in the flooding buffer increases the tolerance of maize seedlings by 1 day when compared to seedlings flooded in the absence of this element. The reason for this longer survival is that calcium maintains the integrity of the cell wall and attenuates the effects of oxidative stress. Owing to this fact, the seedlings remained alive and firm for up to 7 days.

RESUMO-Neste trabalho, foram testados cinco métodos de extração de RNA (CTAB microextração, Concert™ Invitrogen, Concert™ Adaptado, TRI Reagente® Sigma e TRI Reagente® Adaptado), em dois diferentes tecidos de milho (mesocótilo e raiz), com o objetivo de estabelecer um método eficiente de extração de RNA, visando posteriormente estudos de expressão gênica. Observou-se que o método Concert,utilizando o protocolo adaptado, foi o mais eficiente para a extração de RNA de ambos os tecidos de plântulas de milho, originando 2351,35 µg por 100 mg de tecido para mesocótilo e 893,75 µg por 100 mg de tecido para raiz, considerando tanto a quantidade como a qualidade das amostras, podendo ser submetidas às etapas posteriores de tratamento com DNAse e construção de cDNA para estudos de expressão gênica. Pôde-se observar que pequenas modificações nos protocolos, como, por exemplo, mudança no tempo e na posição dos tubos durante a incubação e o incremento de duas lavagens com clorofórmio, podem melhorar muito tanto a qualidade quanto a quantidade do RNA extraído.

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