Citrus is a large genus that includes several major cultivated species, including C. sinensis (sweet orange), Citrus reticulata (tangerine and mandarin), Citrus limon (lemon), Citrus grandis (pummelo) and Citrus paradisi (grapefruit). In 2009, the global citrus acreage was 9 million hectares and citrus production was 122.3 million tons (FAO statistics, see URLs), which is the top ranked among all the fruit crops. Among the 10.9 million tons (valued at $9.3 billion) of citrus products traded in 2009, sweet orange accounted for approximately 60% of citrus production for both fresh fruit and processed juice consumption (FAO statistics, see URLs). Moreover, citrus fruits and juice are the prime human source of vitamin C, an important component of human nutrition.Citrus fruits also have some unique botanical features, such as nucellar embryony (nucellus cells can develop into apomictic embryos that are genetically identical to mother plant). Consequently, somatic embryos grow much more vigorously than the zygotic embryos in seeds such that seedlings are essentially clones of the maternal parent. Such citrus-unique characteristics have hindered the study of citrus genetics and breeding improvement 1,2 . Complete genome sequences would provide valuable genetic resources for improving citrus crops.Citrus is believed to be native to southeast Asia 3-5 , and cultivation of fruit crops occurred at least 4,000 years ago 3,6 . The genetic origin of the sweet orange is not clear, although there are some speculations that sweet orange might be derived from interspecific hybridization of some primitive citrus species 7,8 . Citrus is also in the order Sapindales, a sister order to the Brassicales in the Malvidae, making it valuable for comparative genomics studies with the model plant Arabidopsis.We aimed to sequence the genome of Valencia sweet orange (C. sinensis cv. Valencia), one of the most important sweet orange varieties cultivated worldwide and grown primarily for orange juice production. Normal sweet oranges are diploids, with nine pairs of chromosomes and an estimated genome size of ~367 Mb 9 . To reduce the complexity of the sequenced genome, we obtained a doublehaploid (dihaploid) line derived from the anther culture of Valencia sweet orange 10 . We first generated whole-genome shotgun pairedend-tag sequence reads from the dihaploid genomic DNA and built a de novo assembly as the citrus reference genome; we then produced shotgun sequencing reads from the parental diploid DNA and mapped the sequences to the haploid reference genome to obtain the complete genome information for Valencia sweet orange. In addition, we conducted comprehensive transcriptome sequencing analyses for four representative tissues using shotgun RNA sequencing (RNA-Seq) to capture all transcribed sequences and paired-end-tag RNA sequencing (RNA-PET) to demarcate the 5′ and 3′ ends of all transcripts. On the basis of the DNA and RNA sequencing data, we characterized the orange genome for its gene content, heterozygosity and evolutionary features. ...

Major depressive disorder (MDD) is a cause of disability that affects approximately 16% of the world's population; however, little is known regarding the underlying biology of this disorder. Animal studies, postmortem brain analyses and imaging studies of patients with depression have implicated glial dysfunction in MDD pathophysiology. However, the molecular mechanisms through which astrocytes modulate depressive behaviors are largely uncharacterized. Here, we identified ATP as a key factor involved in astrocytic modulation of depressive-like behavior in adult mice. We observed low ATP abundance in the brains of mice that were susceptible to chronic social defeat. Furthermore, we found that the administration of ATP induced a rapid antidepressant-like effect in these mice. Both a lack of inositol 1,4,5-trisphosphate receptor type 2 and transgenic blockage of vesicular gliotransmission induced deficiencies in astrocytic ATP release, causing depressive-like behaviors that could be rescued via the administration of ATP. Using transgenic mice that express a Gq G protein-coupled receptor only in astrocytes to enable selective activation of astrocytic Ca(2+) signaling, we found that stimulating endogenous ATP release from astrocytes induced antidepressant-like effects in mouse models of depression. Moreover, we found that P2X2 receptors in the medial prefrontal cortex mediated the antidepressant-like effects of ATP. These results highlight astrocytic ATP release as a biological mechanism of MDD.

BACKGROUNDThe outbreak of COVID-19 has laid unprecedented psychological stress on health workers (HWs). We aimed to assess the immediate psychological impact on HWs at Tongji Hospital in Wuhan, China.

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