Wild relatives of cultivated tomato (Solanum lycopersicum) are resistant to a wide range of abiotic and biotic stress conditions. In an effort to understand the molecular mechanisms of salt stress resistance in the wild and cultivated Solanum species, a basic leucine zipper (bZIP) transcription factor was identified in S. chilense, S. peruvianum and S. lycopersicum and named ScAREB1, SpAREB1 and SlAREB1, respectively. Deduced amino acid sequences of the three proteins are 97% identical among them and present high homology with the ABF/AREB subfamily of transcription factors described in different plant species, including Arabidopsis (ABF2, 54% identical) and tobacco (PHI-2, 50% identical). Expression of these orthologous genes is upregulated similarly in the three species by salt stress. The expression of SlAREB1 was further investigated in S. lycopersicum and found to be induced by drought, cold and abscisic acid. To investigate the possible role of this transcription factor in response to abiotic stress, a simple transient expression assay was used for rapid analysis of genes regulated by SlAREB1 in tomato and tobacco by means of Agrobacterium-mediated transformation. Tobacco leaves expressing SlAREB1 showed upregulation of stress-responsive genes such as RD29B, the LEA genes ERD10B and TAS14, the transcription factor PHI-2 and a trehalose-6-phosphate phosphatase gene. These results suggest that this class of bZIP plays a role in abiotic stress response in the Solanum genus.

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We have previously shown that high density lipoprotein is the most abundant protein in the carp plasma and displays bactericidal activity in vitro. Therefore the aim of this study was to analyze the contribution of its principal apolipoproteins, apoA-I and apoA-II, in defense. Both apolipoproteins were isolated by a two step procedure involving affinity and gel filtration chromatography and were shown to display bactericidal and/or bacteriostatic activity in the micromolar range against Gram-positive and Gram-negative bacteria, including some fish pathogens. In addition, a cationic peptide derived from the C-terminal region of carp apoA-I was synthesized and shown to posses antimicrobial activity (EC 50 ¼ 3-6 lM) against Planococcus citreus. This peptide was also able to potentiate the inhibitory effect of lysozyme in a radial diffusion assay at subinhibitory concentrations of both effectors. Finally, limited proteolysis of HDL-associated apoA-I with chymotrypsin in vitro was shown to generate a major truncated fragment, which indicates that apoA-I peptides liberated in vivo through a regulated proteolysis could also be involved in innate immunity.

Casaretto, JA (reprint author), Univ Talca, Inst Biol Vegetal & Biotecnol, Talca, Chile.Growing evidence suggests that the phytohormone abscisic acid (ABA) plays a role in fruit development. ABA signaling components of developmental programs and responses to stress conditions include the group of basic leucine zipper transcriptional activators known as ABA-response element binding factors (AREBs/ABFs). AREB transcription factors mediate ABA-regulated gene expression involved in desiccation tolerance and are expressed mainly in seeds and in vegetative tissues under stress; however, they are also expressed in some fruits such as tomato. In order to get an insight into the role of ABA signaling in fruit development, the expression of two AREB-like factors were investigated during different developmental stages. In addition, tomato transgenic lines that overexpress and downregulate one AREB-like transcription factor, SlAREB1, were used to determine its effect on the levels of some metabolites determining fruit quality. Higher levels of citric acid, malic acid, glutamic acid, glucose and fructose were observed in SlAREB1-overexpressing lines compared with those in antisense suppression lines in red mature fruit pericarp. The higher hexose concentration correlated with increased expression of genes encoding a vacuolar invertase (EC 3.2.1.26) and a sucrose synthase (EC 2.4.1.13). No significant changes were found in ethylene content which agrees with the normal ripening phenotype observed in transgenic fruits. These results suggest that an AREB-mediated ABA signal affects the metabolism of these compounds during the fruit developmental program

Artículo de publicación ISIRoot hypoxia in fruit trees affects growth, vegetative development, and reproductive development, which is reflected in low productivity, poor fruit quality, and premature decay of trees. Using Illumina Hiseq2000, we performed transcriptome analysis of roots from two different rootstocks, ‘Mariana 2624’ and ‘Mazzard F12/1,’ which are tolerant and sensitive to hypoxia, respectively. Transcriptomes from control and hypoxia-stressed plants (6, 24, and 72 h) were compared, using Prunus persica (L.) as reference genome. Hypoxic conditions altered the transcription in both genotypes. There were a high number of common differentially expressed genes (DEG) between the two genotypes for each sampling time, but also exclusive DEG for each genotype, with a few DEG that presented opposite modes of regulations during the hypoxia treatment. An important group of DEGs exclusively upregulated in the tolerant genotype are associated to enzymes of posttranslational protein modifications, such as leucinerich repeat (LRR), kinases and ubiquitin-protein ligases, regulation of transcription, and process of oxide reduction. Singular enrichment analysis of gene ontology (GO), detected at least 115 GOs involved in the response to root hypoxia in the sensitive and/or tolerant genotypes. At least 25 GOs were identified as part of the baseline differences between the genotypes, most GO were disturbed in the sensitive genotype. The contribution from the baseline gene expression to the differential response between the Prunus genotypes is evidence that the resistant genotype is already Bprepared^ for a hypoxia event. An example are GO BP:0042221 of response to chemical stimulus; BP:0006979 of response to oxidative stress; MF:0016209 of antioxidant activity; MF:0016684 of oxidoreductase activity, acting on peroxide as acceptor; and MF:0004601 of peroxidase activity, which were disturbed only in the sensitive genotype, but not in the tolerant.FONDECYT (No. 1121117) and CEAF_R08I100

SummaryMetabolite contents and expression of genes of primary metabolism are described in tomato fruits with different SlAREB1 expression levels. Participation of this transcription factor and abscisic acid signalling in metabolic programming during fruit ripening is suggested.

Hexokinases (HXKs) and fructokinases (FRKs) are the only two families of enzymes in plants that have been identified as able to phosphorylate Glucose (Glc) and Fructose (Fru). Glc can only be phosphorylated in plants by HXKs, while Fru can be phosphorylated by either HXKs or FRKs. The various subcellular localizations of HXKs in plants indicate that they are involved in diverse functions, including anther dehiscence and pollen germination, stomatal closure in response to sugar levels, stomatal aperture and reducing transpiration. Its association with modulating programmed cell death, and responses to oxidative stress and pathogen infection (abiotic and biotic stresses) also have been reported. To extend our understanding about the function of HXK-like genes in the response of Prunus rootstocks to abiotic stress, we performed a detailed bioinformatic and functional analysis of hexokinase 3-like genes (HXK3s) from two Prunus rootstock genotypes, ‘M.2624’ (Prunus cerasifera Ehrh × P. munsoniana W.Wight & Hedrick) and ‘M.F12/1’ (P. avium L.), which are tolerant and sensitive to hypoxia stress, respectively. A previous large-scale transcriptome sequencing of roots of these rootstocks, showed that this HXK3-like gene that was highly induced in the tolerant genotype under hypoxia conditions. In silico analysis of gene promoters from M.2624 and M.F12/1 genotypes revealed regulatory elements that could explain differential transcriptional profiles of HXK3 genes. Subcellular localization was determinates by both bioinformatic prediction and expression of their protein fused to the green fluorescent protein (GFP) in protoplasts and transgenic plants of Arabidopsis. Both approaches showed that they are expressed in plastids. Metabolomics analysis of Arabidopsis plants ectopically expressing Prunus HXK3 genes revealed that content of several metabolites including phosphorylated sugars (G6P), starch and some metabolites associated with the TCA cycle were affected. These transgenic Arabidopsis plants showed improved tolerance to salt and drought stress under growth chamber conditions. Our results suggest that Prunus HXK3 is a potential candidate for enhancing tolerance to salt and drought stresses in stone fruit trees and other plants.

Maqui (Aristotelia chilensis [Molina] Stunz) is a small dioecious tree native to South America with edible fruit characterized by very high antioxidant capacity and anthocyanin content. To preserve maqui as a genetic resource it is essential to study its genetic diversity. However, the complete genome is unknown and only a few gene sequences are available in databases. Simple sequence repeats (SSR) markers, which are neutral, co-dominant, reproducible and highly variable, are desirable to support genetic studies in maqui populations. By means of identification and characterization of microsatellite loci from a maqui genotype, using 454 sequencing technology, we develop a set of SSR for this species. Obtaining a total of 165,043 shotgun genome sequences, with an average read length of 387 bases, we covered 64 Mb of the maqui genome. Reads were assembled into 4,832 contigs, while 98,546 reads remained as singletons, generating a total of 103,378 consensus genomic sequences. A total of 24,494 SSR maqui markers were identified. Of them, 15,950 SSR maqui markers were classified as perfects. The most common SSR motifs were dinucleotide (31%), followed by tetranucleotide (26%) and trinucleotide motifs (24%). The motif AG/CT (28.4%) was the most abundant, while the motif AC (89 bp) was the largest. Eleven polymorphic SSRs were selected and used to analyze a population of 40 maqui genotypes. Polymorphism information content (PIC) ranged from 0.117 to 0.82, with an average of 0.58. Non-significant groups were observed in the maqui population, showing a panmictic genetic structure. In addition, we also predicted 11150 putative genes and 3 microRNAs (miRNAs) in maqui sequences. This results, including partial sequences of genes, some miRNAs and SSR markers from high throughput next generation sequencing (NGS) of maqui genomic DNA, constitute the first platform to undertake genetic and molecular studies of this important species.