Citrus is the first tree crop in terms of fruit production. The colour of Citrus fruit is one of the main quality attributes, caused by the accumulation of carotenoids and their derivative C30 apocarotenoids, mainly β-citraurin (3-hydroxy-β-apo-8′-carotenal), which provide an attractive orange-reddish tint to the peel of oranges and mandarins. Though carotenoid biosynthesis and its regulation have been extensively studied in Citrus fruits, little is known about the formation of C30 apocarotenoids. The aim of this study was to the identify carotenoid cleavage enzyme(s) [CCD(s)] involved in the peel-specific C30 apocarotenoids. In silico data mining revealed a new family of five CCD4-type genes in Citrus. One gene of this family, CCD4b1, was expressed in reproductive and vegetative tissues of different Citrus species in a pattern correlating with the accumulation of C30 apocarotenoids. Moreover, developmental processes and treatments which alter Citrus fruit peel pigmentation led to changes of β-citraurin content and CCD4b1 transcript levels. These results point to the involvement of CCD4b1 in β-citraurin formation and indicate that the accumulation of this compound is determined by the availability of the presumed precursors zeaxanthin and β-cryptoxanthin. Functional analysis of CCD4b1 by in vitro assays unequivocally demonstrated the asymmetric cleavage activity at the 7′,8′ double bond in zeaxanthin and β-cryptoxanthin, confirming its role in C30 apocarotenoid biosynthesis. Thus, a novel plant carotenoid cleavage activity targeting the 7′,8′ double bond of cyclic C40 carotenoids has been identified. These results suggest that the presented enzyme is responsible for the biosynthesis of C30 apocarotenoids in Citrus which are key pigments in fruit coloration.

BackgroundComparative transcriptomics and functional studies of different Saccharomyces species have opened up the possibility of studying and understanding new yeast abilities. This is the case of yeast adaptation to stress, in particular the cold stress response, which is especially relevant for the food industry. Since the species Saccharomyces kudriavzevii is adapted to grow at low temperatures, it has been suggested that it contains physiological adaptations that allow it to rapidly and efficiently acclimatise after cold shock.ResultsIn this work, we aimed to provide new insights into the molecular basis determining this better cold adaptation of S. kudriavzevii strains. To this end, we have compared S. cerevisiae and S. kudriavzevii transcriptome after yeast adapted to cold shock. The results showed that both yeast mainly activated the genes related to translation machinery by comparing 12°C with 28°C, but the S. kudriavzevii response was stronger, showing an increased expression of dozens of genes involved in protein synthesis. This suggested enhanced translation efficiency at low temperatures, which was confirmed when we observed increased resistance to translation inhibitor paromomycin. Finally, 35S-methionine incorporation assays confirmed the increased S. kudriavzevii translation rate after cold shock.ConclusionsThis work confirms that S. kudriavzevii is able to grow at low temperatures, an interesting ability for different industrial applications. We propose that this adaptation is based on its enhanced ability to initiate a quick, efficient translation of crucial genes in cold adaptation among others, a mechanism that has been suggested for other microorganisms.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-432) contains supplementary material, which is available to authorized users.

Pregnancy and parturition are associated with opioid-mediated elevations in maternal pain thresholds. This analgesia is subserved by a spinal cord dynorphin/K-opiate receptor system. During gestation, elevated pain thresholds are paralleled by a significant increase in the content of dynorphin (1–17 and 1–8) in the lumbar spinal cord. An additional increment in lumbar dynorphin (1–17) concentration, but not that of dynorphin (1–8), occurs in parturient animals. Simulation of the pregnancy blood concentration profile of 17β-estradiol and progesterone (‘hormone-simulated pregnancy’) also results in an opioid analgesia, the magnitude and temporal pattern of which closely approximates that of actual gestation. The current study demonstrates that during hormone-simulated pregnancy, the spinal cord content of dynorphin (1–17) [but not dynorphin (1–8)] is positively modulated. This regulation is time- (or dose-)-dependent and region-specific. Significant elevations in spinal levels of dynorphin (1–17) are observed during steroid dose periods 3 and 4, corresponding to the last week of actual gestation and parturition, respectively. Increased dynorphin (1–17) content is observed in only the lumbar spinal region. These changes are temporally and anatomically identical to those which occur during actual gestation and parturition. It is concluded that changes in circulating 17β-estradiol and progesterone, that occur as a natural consequence of gestation, activate a dynorphin system in the lumbar spinal cord. This attenuates the pain associated with late pregnancy and labor. The pattern of circulating sex steroids can be an important determinant of the activity of central opioid analgesic systems.

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