We present a quantum key distribution system with a 2.5 GHz repetition rate using a threestate time-bin protocol combined with a one-decoy approach. Taking advantage of superconducting single-photon detectors optimized for quantum key distribution and ultra low-loss fiber, we can distribute secret keys at a maximum distance of 421 km and obtain secret key rates of 6.5 bps over 405 km.

Human selection has reshaped crop genomes. Here we report an apple genome variation map generated through genome sequencing of 117 diverse accessions. A comprehensive model of apple speciation and domestication along the Silk Road is proposed based on evidence from diverse genomic analyses. Cultivated apples likely originate from Malus sieversii in Kazakhstan, followed by intensive introgressions from M. sylvestris. M. sieversii in Xinjiang of China turns out to be an “ancient” isolated ecotype not directly contributing to apple domestication. We have identified selective sweeps underlying quantitative trait loci/genes of important fruit quality traits including fruit texture and flavor, and provide evidences supporting a model of apple fruit size evolution comprising two major events with one occurring prior to domestication and the other during domestication. This study outlines the genetic basis of apple domestication and evolution, and provides valuable information for facilitating marker-assisted breeding and apple improvement.

Both sorbitol and sucrose are imported into apple fruit from leaves. The metabolism of sorbitol and sucrose fuels fruit growth and development, and accumulation of sugars in fruit is central to the edible quality of apple. However, our understanding of the mechanisms controlling sugar metabolism and accumulation in apple remains quite limited. We identified members of various gene families encoding key enzymes or transporters involved in sugar metabolism and accumulation in apple fruit using homology searches and comparison of their expression patterns in different tissues, and analyzed the relationship of their transcripts with enzyme activities and sugar accumulation during fruit development. At the early stage of fruit development, the transcript levels of sorbitol dehydrogenase, cell wall invertase, neutral invertase, sucrose synthase, fructokinase and hexokinase are high, and the resulting high enzyme activities are responsible for the rapid utilization of the imported sorbitol and sucrose for fruit growth, with low levels of sugar accumulation. As the fruit continues to grow due to cell expansion, the transcript levels and activities of these enzymes are down-regulated, with concomitant accumulation of fructose and elevated transcript levels of tonoplast monosaccharide transporters (TMTs), MdTMT1 and MdTMT2; the excess carbon is converted into starch. At the late stage of fruit development, sucrose accumulation is enhanced, consistent with the elevated expression of sucrose-phosphate synthase (SPS), MdSPS5 and MdSPS6, and an increase in its total activity. Our data indicate that sugar metabolism and accumulation in apple fruit is developmentally regulated. This represents a comprehensive analysis of the genes involved in sugar metabolism and accumulation in apple, which will serve as a platform for further studies on the functions of these genes and subsequent manipulation of sugar metabolism and fruit quality traits related to carbohydrates.

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We examined whether exogenously applied melatonin could improve resistance to Marssonina apple blotch (Diplocarpon mali) by apple [Malus prunifolia (Willd.) Borkh. cv. Donghongguo]. This serious disease leads to premature defoliation in the main regions of apple production. When plants were pretreated with melatonin, resistance was increased in the leaves. We investigated the potential roles for melatonin in modulating levels of hydrogen peroxide (H2O2), as well the activities of antioxidant enzymes and pathogenesis-related proteins during these plant-pathogen interactions. Pretreatment enabled plants to maintain intracellular H2O2 concentrations at steady-state levels and enhance the activities of plant defence-related enzymes, possibly improving disease resistance. Because melatonin is safe and beneficial to animals and humans, exogenous pretreatment might represent a promising cultivation strategy to protect plants against this pathogen infection.

Twin field quantum key distribution promises high key rates at long distance to beat the rate distance limit. Here, applying the sending or not sending TF QKD protocol, we experimentally demonstrate a secure key distribution breaking the absolute key rate limit of repeaterless QKD over 509 km, 408 km ultra-low loss optical fibre and 350 km standard optical fibre. Two independent lasers are used as the source with remote frequency locking technique over 500 km fiber distance; Practical optical fibers are used as the optical path with appropriate noise filtering; And finite key effects are considered in the key rate analysis. The secure key rates obtained at different distances are more than 5 times higher than the conditional limit of repeaterless QKD, a bound value assuming the same detection loss in the comparison. The achieved secure key rate is also higher than that a traditional QKD protocol running with a perfect repeaterless QKD device and even if an infinite number of sent pulses. Our result shows that the protocol and technologies applied in this experiment enable TF QKD to achieve high secure key rate at long distribution distance, and hence practically useful for field implementation of intercity QKD.Introduction.-Channel loss seems to be the most severe limitation on the practical application of long distance quantum key distribution (QKD) [1-3], given that quantum signals cannot be amplified. Much efforts have been made towards the goal of a longerdistance for QKD [4][5][6]. Theoretically, the decoy-state method [7][8][9] can improve the key rate of coherent-state based QKD from scaling quadratically to a linear with the channel transmittance, as what behaves of a perfect single-photon source. This method can beat the photonnumber-splitting attack to the imperfect single-photon source and the coherent state is used as if only those single-photon pulses were used for key distillation, and hence it can reach the key rate to a level comparable with that of a perfect single-photon source.

Ripening is a programmed process involving substantial changes in fruit quality properties, such as color, aroma, flavor, and texture (Prasanna et al., 2007; Klee and Giovannoni, 2011). The overall process of fruit ripening, however, is that of senescence, accompanied by fruit quality deterioration and postharvest loss (Seymour et al., 2013). Thus, the postharvest control of ripening is critical for the fruit industry. In tomato (Solanum lycopersicum), multiple regulators of fruit ripening have been identified, such as Ripening-inhibitor (RIN; Vrebalov et al., 2002), Colorless nonripening (CNR; Manning et al., 2006), Never-ripe (Nr; Wilkinson et al., 1995), APETALA2a (AP2a; Karlova et al., 2011), etc. Transgenic studies of such genes in tomato fruit, or the use of mutants, has shown the impacts of these genes on fruit ripening. However, such studies have been less frequent in other fruit crops, especially perennial fruit, where transgenic studies and the availability of mutants are limited. Moreover, the function of these ripening regulators may differ in various crops, as the tomato rin mutant (Vrebalov et al., 2002) and FaMADS9 (MCM1/AGAMOUS/DEFICIENS/SRF [MADS] box) antisense transgenic strawberry (Fragaria × ananassa) fruit (Seymour et al., 2011) inhibit or retard ripening, while MdMADS8/9-suppressed apple (Malus × domestica) has a phenotype of small fruit with reduced flesh (Ireland et al., 2013). These findings highlight the need for investigations of ripening regulation in different fruit types and species.

Multimode fibres (MMFs) are attracting interest for complex spatiotemporal dynamics, and for ultrafast fibre sources, imaging and telecommunications. This new interest is based on three key properties: their high spatiotemporal complexity (information capacity), the important role of disorder, and complex intermodal interactions. To date, phenomena in MMFs have been studied only in limiting cases where one or more of these properties can be neglected. Here we study MMFs in a regime in which all these elements are integral. We observe a spatial beam-cleaning process preceding spatiotemporal modulation instability. We show that the origin of these processes is a universal unstable attractor in graded-index MMFs. Both the self-organization of the attractor, as well as its instability, are caused by intermodal interactions characterized by cooperating disorder, nonlinearity and dissipation. The demonstration of a disorder-enhanced nonlinear process in MMF has important implications for telecommunications, and the multifaceted complexity of the dynamics showcases MM waveguides as ideal laboratories for many topics and applications in complexity science.Comment: http://www.nature.com/nphoton/journal/v10/n12/full/nphoton.2016.227.htm