Short-chain acyl-CoA oxidases are ␤-oxidation enzymes that are active on short-chain acyl-CoAs and that appear to be present in higher plant peroxisomes and absent in mammalian peroxisomes. Therefore, plant peroxisomes are capable of performing complete ␤-oxidation of acyl-CoA chains, whereas mammalian peroxisomes can perform ␤-oxidation of only those acyl-CoA chains that are larger than octanoyl-CoA (C 8 ). In this report, we have shown that a novel acyl-CoA oxidase can oxidize short-chain acyl-CoA in plant peroxisomes. A peroxisomal short-chain acyl-CoA oxidase from Arabidopsis was purified following the expression of the Arabidopsis cDNA in a baculovirus expression system. The purified enzyme was active on butyryl-CoA (C 4 ), hexanoyl-CoA (C 6 ), and octanoyl-CoA (C 8 ). Cell fractionation and immunocytochemical analysis revealed that the short-chain acyl-CoA oxidase is localized in peroxisomes. The expression pattern of the short-chain acylCoA oxidase was similar to that of peroxisomal 3-ketoacyl-CoA thiolase, a marker enzyme of fatty acid ␤-oxidation, during post-germinative growth. Although the molecular structure and amino acid sequence of the enzyme are similar to those of mammalian mitochondrial acyl-CoA dehydrogenase, the purified enzyme has no activity as acyl-CoA dehydrogenase. These results indicate that the short-chain acyl-CoA oxidases function in fatty acid ␤-oxidation in plant peroxisomes, and that by the cooperative action of long-and short-chain acylCoA oxidases, plant peroxisomes are capable of performing the complete ␤-oxidation of acyl-CoA.Oilseed plants convert reserve oil to sucrose after germination. This unique type of gluconeogenesis occurs in the storage tissues of oilseeds, such as endosperms or cotyledons (1). The metabolic pathway involves many enzymes in several subcellular compartments, including lipid bodies, glyoxysomes (a specialized peroxisome), mitochondria, and the cytosol. Within the entire gluconeogenic pathway, the conversion of a fatty acid to succinate takes place within the glyoxysomes, which contain enzymes for fatty acid ␤-oxidation and the glyoxylate cycle.Glyoxysomes and leaf peroxisomes are members of a group of organelles called peroxisomes (2). In glyoxysomes, fatty acids are first activated to fatty acyl-CoA by fatty acyl-CoA synthetase (3). Fatty acyl-CoA is the substrate for fatty acid ␤-oxidation, which consists of four enzymatic reactions (4). The first reaction is catalyzed by acyl-CoA oxidase. The second and third enzymatic reactions are catalyzed by a single enzyme that possesses enoyl-CoA hydratase and ␤-hydroxyacyl-CoA dehydrogenase activities (5). The fourth reaction is catalyzed by 3-ketoacyl-CoA thiolase (referred to as thiolase below) (6). Acetyl-CoA, an end product of fatty acid ␤-oxidation, is metabolized further to produce succinate by the glyoxylate cycle.In mammalian cells, both peroxisomes and mitochondria contain a functional fatty acid ␤-oxidation system. In peroxisomes, the first enzyme of fatty acid ␤-oxidation, acyl-CoA oxidase, donates...

Background: Water stress during grain filling has a marked effect on grain yield, leading to a reduced endosperm cell number and thus sink capacity to accumulate dry matter. The bread wheat cultivar Chinese Spring (CS), a Chinese Spring terminal deletion line (CS_5AL-10) and the durum wheat cultivar Creso were subjected to transcriptional profiling after exposure to mild and severe drought stress at the grain filling stage to find evidences of differential stress responses associated to different wheat genome regions.

Betacyanin (betanin), total phenolics, vitamin C and antioxidant capacity (by Trolox-equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) assays) were investigated in two differently colored cactus pear (Opuntia ficus-indica (L.) Mill.) genotypes, one with purple fruit and the other with orange fruit, from the Salento area, in Apulia (South Italy). In order to quantitate betanin in cactus pear fruit extracts (which is difficult by HPLC because of the presence of two isomers, betanin and isobetanin, and the lack of commercial standard with high purity), betanin was purified from Amaranthus retroflexus inflorescence, characterized by the presence of a single isomer. The purple cactus pear variety showed very high betanin content, with higher levels of phenolics, vitamin C, and antioxidant capacity (TEAC) than the orange variety. These findings confirm the potential for exploiting the autochthonous biodiversity of cactus pear fruits. In particular, the purple variety could be an interesting source of colored bioactive compounds which not only have coloring potential, but are also an excellent source of dietary antioxidant components which may have beneficial effects on consumers’ health.

BackgroundDurum wheat often faces water scarcity and high temperatures, two events that usually occur simultaneously in the fields. Here we report on the stress responsive strategy of two durum wheat cultivars, characterized by different water use efficiency, subjected to drought, heat and a combination of both stresses.ResultsThe cv Ofanto (lower water use efficiency) activated a large set of well-known drought-related genes after drought treatment, while Cappelli (higher water use efficiency) showed the constitutive expression of several genes induced by drought in Ofanto and a modulation of a limited number of genes in response to stress. At molecular level the two cvs differed for the activation of molecular messengers, genes involved in the regulation of chromatin condensation, nuclear speckles and stomatal closure. Noteworthy, the heat response in Cappelli involved also the up-regulation of genes belonging to fatty acid β-oxidation pathway, glyoxylate cycle and senescence, suggesting an early activation of senescence in this cv. A gene of unknown function having the greatest expression difference between the two cultivars was selected and used for expression QTL analysis, the corresponding QTL was mapped on chromosome 6B.ConclusionOfanto and Cappelli are characterized by two opposite stress-responsive strategies. In Ofanto the combination of drought and heat stress led to an increased number of modulated genes, exceeding the simple cumulative effects of the two single stresses, whereas in Cappelli the same treatment triggered a number of differentially expressed genes lower than those altered in response to heat stress alone. This work provides clear evidences that the genetic system based on Cappelli and Ofanto represents an ideal tool for the genetic dissection of the molecular response to drought and other abiotic stresses.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-14-821) contains supplementary material, which is available to authorized users.

The ability to sense sugars is crucial for the modulation of gene expression in plants. Despite the importance of this phenomenon, our knowledge of sugar sensing in plants is scant. Several valuable hypotheses have been put forward based on the extensive knowledge of sugar sensing in yeast. In recent years, tests of these hypotheses have shown that hexokinase and sucrose-non-fermenting-(SNF-) related proteins appear to be involved in sugar sensing and transduction, not only in yeast but also in higher plants. However, even if plants share with yeast some elements involved in sugar sensing, several aspects of sugar perception are likely to be peculiar to higher plants. Plants should be able to sense not only glucose but also other hexoses, such as fructose and disaccharides (sucrose, maltose and others). In this Botanical Brie®ng we outline recent discoveries in this ®eld, with emphasis on arabidopsis and cereals. The use of transgenic plants and mutants to identify sugar sensor(s) and elements in the signalling pathways and their cross-talk with the hormonal signalling is discussed.

No abstract

We have developed a vision-based program to detect symptoms of Olive Quick Decline Syndrome (OQDS) on leaves of Olea europaea L. infected by Xylella fastidiosa, named X-FIDO (Xylella FastIdiosa Detector for O. europaea L.). Previous work predicted disease from leaf images with deep learning but required a vast amount of data which was obtained via crowd sourcing such as the PlantVillage project. This approach has limited applicability when samples need to be tested with traditional methods (i.e., PCR) to avoid incorrect training input or for quarantine pests which manipulation is restricted. In this paper, we demonstrate that transfer learning can be leveraged when it is not possible to collect thousands of new leaf images. Transfer learning is the re-application of an already trained deep learner to a new problem. We present a novel algorithm for fusing data at different levels of abstraction to improve performance of the system. The algorithm discovers low-level features from raw data to automatically detect veins and colors that lead to symptomatic leaves. The experiment included images of 100 healthy leaves, 99 X. fastidiosa-positive leaves and 100 X. fastidiosa-negative leaves with symptoms related to other stress factors (i.e., abiotic factors such as water stress or others diseases). The program detects OQDS with a true positive rate of 98.60 ± 1.47% in testing, showing great potential for image analysis for this disease. Results were obtained with a convolutional neural network trained with the stochastic gradient descent method, and ten trials with a 75/25 split of training and testing data. This work shows potential for massive screening of plants with reduced diagnosis time and cost.

Crenothrix polyspora Cohn 1870 and Clonothrix fusca Roze 1896 are two filamentous, sheathed microorganisms exhibiting complex morphological differentiation, whose phylogeny and physiology have been obscure for a long time due to the inability to cultivate them. Very recently, DNA sequencing data from uncultured C. polyspora-enriched material have suggested that Crenothrix is a methane-oxidizing ␥-proteobacterium (39). In contrast, the possible ecological function of C. fusca, originally considered a developmental stage of C. polyspora, is unknown. In this study, temporal succession of two filamentous, sheathed microorganisms resembling Cohn's Crenothrix and Roze's Clonothrix was observed by analyzing the microbial community of an artesian well by optical microscopy. Combined culture-based and culture-independent approaches enabled us to assign C. fusca to a novel subgroup of methane-oxidizing ␥-proteobacteria distinct from that of C. polyspora. This assignment was supported by (i) methane uptake and assimilation experiments, (ii) ultrastructural data showing the presence in C. fusca cytoplasm of an elaborate membrane system resembling that of methanotrophic ␥-proteobacteria, and (iii) sequencing data demonstrating the presence in its genome of a methanol dehydrogenase ␣ subunit-encoding gene (mxaF) and a conventional particulate methane mono-oxygenase ␣ subunit-encoding gene (pmoA) that is different from the unusual pmoA (u-pmoA) of C. polyspora.