On the world stage, the increase in temperatures due to global warming is already a reality that has become one of the main challenges faced by the scientific community. Since agriculture is highly dependent on climatic conditions, it may suffer a great impact in the short term if no measures are taken to adapt and mitigate the agricultural system. Plant responses to abiotic stresses have been the subject of research by numerous groups worldwide. Initially, these studies were concentrated on model plants, and, later, they expanded their studies in several economically important crops such as rice, corn, soybeans, coffee, and others. However, agronomic evaluations for the launching of cultivars and the classical genetic improvement process focus, above all, on productivity, historically leaving factors such as tolerance to abiotic stresses in the background. Considering the importance of the impact that abiotic stresses can have on agriculture in the short term, new strategies are currently being sought and adopted in breeding programs to understand the physiological, biochemical, and molecular responses to environmental disturbances in plants of agronomic interest, thus ensuring the world food security. Moreover, integration of these approaches is bringing new insights on breeding. We will discuss how water deficit, high temperatures, and salinity exert effects on plants.

Abiotic stresses are among the most important factors that affect food production. One important step to face these environmental challenges is the transcriptional modulation. Quantitative real-time PCR is a rapid, sensitive, and reliable method for the detection of mRNAs and it has become a powerful tool to mitigate plant stress tolerance; however, suitable reference genes are required for data normalization. Reference genes for coffee plants during nitrogen starvation, salinity and heat stress have not yet been reported. We evaluated the expression stability of ten candidate reference genes using geNorm PLUS, NormFinder, and BestKeeper softwares, in plants submitted to nitrogen starvation, salt and heat stress. EF1, EF1α, GAPDH, MDH, and UBQ10 were ranked as the most stable genes in all stresses and software analyses, while RPL39 and RPII were classified as the less reliable references. For reference gene validation, the transcriptional pattern of a Coffea non-symbiotic hemoglobin (CaHb1) was analyzed using the two new recommended and the most unstable gene references for normalization. The most unstable gene may lead to incorrect interpretation of CaHb1 transcriptional analysis. Here, we recommend two new reference genes in Coffea for use in data normalization in abiotic stresses: MDH and EF1.

ABSTRACT

ResumoCom o objetivo de avaliar o potencial de enraizamento da seleção 8501-9 de goiabeira utilizou-se estacas herbáceas com 10-12 cm de comprimento em duas formas de preparo (corte simples sem lesão e exposição do câmbio) e três intensidades de supressão das folhas (sem folhas, com folhas cortadas ao meio e folhas intactas). O delineamento experimental foi inteiramente casualizado com cinco repetições em arranjo fatorial 2 x 3, com dez estacas por parcela. Após tratamento com AIB as estacas foram colocadas para enraizamento em caixas plásticas (44 x 30 x 7 cm) contendo casca de arroz carbonizada, em câmara de nebulização. Após 78 dias avaliou-se a retenção foliar, a sobrevivência das estacas, o número de estacas enraizadas e de raízes, o comprimento e as massas fresca e seca das raízes. A interação entre lesão e presença de folhas não foi significativa, indicando que estes fatores agem de forma independente em relação aos fatores estudados. A supressão das folhas resultou em morte das estacas. A exposição do câmbio não proporcionou vantagens no enraizamento de estacas herbáceas. As estacas com um par de folhas inteiras apresentaram maiores massas fresca e seca de raízes em relação às estacas com folhas cortadas, já as estacas sem folhas não apresentaram formação de raízes, sendo a presença de folhas fundamental para a promoção do enraizamento. Palavras-chave: Psidium guajava L, reguladores vegetais, propagação vegetal AbstractWith the objective of evaluate the potential of rooting of the selection of guava tree 8501-9 were using herbaceous cutting with 10-12 cm of length in two make of the prepared (simple cut without lesions and cambium exposition), and three suppression intensity of the leaves (without leaves, with half leaves and intact leaves). The experimental design was completely randomized with five repetitions in factorial arrangement 2 x 3, with ten cutting for parcel. After the preparation with IBA the cutting had been placed to rooting in plastic box (44 x 30 x 7 cm) with carbonized rice hulls, in camera of nebulization. After 78 days, evaluated the leaf retention, survive of the cutting, the number of cutting roots and of roots, the length and fresh and dry mass of the roots. The interaction between lesions and presence of leaves was not significant, indicating like this factors act in independent form in relation the study factors. The leaves suppression resulted in cutting death. The cambium exposition not proportion vantage on root cutting herbaceous. For the gotten results it was observed that the interaction between lesion and leaf presence was not significant, indicating that these factors act of independent form in relation to the evaluated parameters. Cutting with base lesion presented addition of only 10% of foliar retention and percentage of roots cutting. Cutting with a pair of leaves had been superior to the parameters of the mass fresh and dry of root in relation to the cutting with half leaves, and the cutting without leaves not presented formation of roots being presence of leaves fu...

ABSTRACT. Sweet orange (Citrus sinensis) plays an important role in the economy of more than 140 countries, but it is grown in areas with intermittent stressful soil and climatic conditions. The stress tolerance could be addressed by manipulating the ethylene response factor (ERF) transcription factors because they orchestrate plant responses to environmental stress. We performed an in silico study on the ERFs in the expressed sequence tag database of C. sinensis to identify potential genes that regulate plant responses to stress. We identified 108 putative genes encoding protein sequences of the AP2/ERF superfamily distributed within 10 groups of amino acid sequences. Ninety-one genes were assembled from the ERF family containing only one AP2/ ERF domain, 13 genes were assembled from the AP2 family containing two AP2/ERF domains, and four other genes were assembled from the RAV family containing one AP2/ERF domain and a B3 domain. Some conserved domains of the ERF family genes were disrupted into a few segments by introns. This irregular distribution of genes in the AP2/ ERF superfamily in different plant species could be a result of genomic losses or duplication events in a common ancestor. The in silico gene expression revealed that 67% of AP2/ERF genes are expressed in tissues with usual plant development, and 14% were expressed in stressed tissues. Because the AP2/ERF superfamily is expressed in an orchestrated way, it is possible that the manipulation of only one gene may result in changes in the whole plant function, which could result in more tolerant crops.