Spinach is an important leafy vegetable enriched with multiple necessary nutrients. Here we report the draft genome sequence of spinach (Spinacia oleracea, 2n=12), which contains 25,495 protein-coding genes. The spinach genome is highly repetitive with 74.4% of its content in the form of transposable elements. No recent whole genome duplication events are observed in spinach. Genome syntenic analysis between spinach and sugar beet suggests substantial inter- and intra-chromosome rearrangements during the Caryophyllales genome evolution. Transcriptome sequencing of 120 cultivated and wild spinach accessions reveals more than 420 K variants. Our data suggests that S. turkestanica is likely the direct progenitor of cultivated spinach and spinach domestication has a weak bottleneck. We identify 93 domestication sweeps in the spinach genome, some of which are associated with important agronomic traits including bolting, flowering and leaf numbers. This study offers insights into spinach evolution and domestication and provides resources for spinach research and improvement.

[1] We developed a 50-year tree ring δ 18 O chronology for each of three tree species (Juniperus indica, Larix griffithii, and Picea spinulosa) using a total of 12 trees (four trees per species) from the Bhutan Himalaya. Despite originating from different species sampled at two different altitudes, the δ 18 O chronologies are highly correlated with one another (r = 0.76-0.89). Response analyses reveal that tree ring δ 18 O values are controlled mainly by summer precipitation, irrespective of species. Based on these results, a robust 269-year δ 18 O chronology was established to reconstruct the amount of May-September precipitation based on data from four larch trees. Our tree ring δ 18 O data show significant correlations with those from other regions of the Himalaya and the Tibetan Plateau, indicating that common signals related to monsoon activity are recorded in the data. However, at centennial timescales, our data from Bhutan show normal conditions during the 20th century, whereas records from sites in western Nepal and the southern/eastern Tibetan Plateau show weakening trends in monsoon intensity during the last 100-200 years; the weakening trends may be the result of a reduction in the meridional sea surface temperature gradient in the Indian Ocean during this time. At continental scales, the tree ring records show that areas more from ocean basins are particularly sensitive to reduced monsoon circulation. Correlation analyses suggest that the El Niño-Southern Oscillation (ENSO) plays an important role in modulating summer precipitation. However, the teleconnected relationship disappears during the period 1951-1970, coinciding with a negative phase of the Pacific Decadal Oscillation (PDO), implying interdecadal modulation of the PDO on the influence of the ENSO on precipitation in Bhutan.

Plant drought tolerance is a complex trait that requires a global view to understand its underlying mechanism. The proteomic aspects of plant drought response have been extensively investigated in model plants, crops and wood plants. In this review, we summarize recent proteomic studies on drought response in leaves to reveal the common and specialized drought-responsive mechanisms in different plants. Although drought-responsive proteins exhibit various patterns depending on plant species, genotypes and stress intensity, proteomic analyses show that dominant changes occurred in sensing and signal transduction, reactive oxygen species scavenging, osmotic regulation, gene expression, protein synthesis/turnover, cell structure modulation, as well as carbohydrate and energy metabolism. In combination with physiological and molecular results, proteomic studies in leaves have helped to discover some potential proteins and/or metabolic pathways for drought tolerance. These findings provide new clues for understanding the molecular basis of plant drought tolerance.

Reproducible climate reconstructions of the Common Era (1 CE to present) are key to placing industrial-era warming into the context of natural climatic variability. Here we present a community-sourced database of temperature-sensitive proxy records from the PAGES2k initiative. The database gathers 692 records from 648 locations, including all continental regions and major ocean basins. The records are from trees, ice, sediment, corals, speleothems, documentary evidence, and other archives. They range in length from 50 to 2000 years, with a median of 547 years, while temporal resolution ranges from biweekly to centennial. Nearly half of the proxy time series are significantly correlated with HadCRUT4.2 surface temperature over the period 1850–2014. Global temperature composites show a remarkable degree of coherence between high- and low-resolution archives, with broadly similar patterns across archive types, terrestrial versus marine locations, and screening criteria. The database is suited to investigations of global and regional temperature variability over the Common Era, and is shared in the Linked Paleo Data (LiPD) format, including serializations in Matlab, R and Python.

Abstract. We have constructed a regional tree-ring cellulose oxygen isotope (δ 18 O) record for the northern Indian subcontinent based on two new records from northern India and central Nepal and three published records from northwestern India, western Nepal and Bhutan. The record spans the common interval from 1743 to 2008 CE. Correlation analysis reveals that the record is significantly and negatively correlated with the three regional climatic indices: all India rainfall (AIR; r = −0.5, p < 0.001, n = 138), Indian monsoon index (IMI; r = −0.45, p < 0.001, n = 51) and the intensity of monsoonal circulation (r = −0.42, p < 0.001, n = 51). The close relationship between tree-ring cellulose δ 18 O and the Indian summer monsoon (ISM) can be explained by oxygen isotope fractionation mechanisms. Our results indicate that the regional tree-ring cellulose δ 18 O record is suitable for reconstructing high-resolution changes in the ISM. The record exhibits significant interannual and long-term variations. Interannual changes are closely related to the El Niño-Southern Oscillation (ENSO), which indicates that the ISM was affected by ENSO in the past. However, the ISM-ENSO relationship was not consistent over time, and it may be partly modulated by Indian Ocean sea surface temperature (SST). Long-term changes in the regional tree-ring δ 18 O record indicate a possible trend of weakened ISM intensity since 1820. Decreasing ISM activity is also observed in various high-resolution ISM records from southwest China and Southeast Asia, and may be the result of reduced land-ocean thermal contrasts since 1820 CE.

Rice is a major staple food worldwide. Making hybrid rice has proved to be an effective strategy to significantly increase grain yield. Current hybrid rice technologies rely on male sterile lines and have been used predominantly in indica cultivars. However, intrinsic problems exist in the implementation of these technologies, such as limited germplasms and unpredictable conversions from sterility to fertility in the field. Here, we describe a photoperiod-controlled male sterile line, carbon starved anther (csa), which contains a mutation in an R2R3 MYB transcription regulator of pollen development. This mutation was introduced into indica and japonica rice, and it rendered male sterility under short-day conditions and male fertility under long-day conditions in both lines. Furthermore, F 1 plants of csa and a restorer line JP69 exhibited heterosis (hybrid vigor), suggesting the feasibility of using this mutation to create hybrid rice. The csabased photoperiod-sensitive male sterile line allows the establishment of a stable two-line hybrid system, which promises to have a significant impact on agriculture.PGMS line | hybrid breeding | sugar partitioning R ice (Oryza sativa L.) is a major staple food that feeds more than one-half of the human population (1). The three-and two-line hybrid rice breeding technologies take advantage of heterosis (hybrid vigor) and have been successfully applied in many countries, leading to a more than 20% yield increase over inbred varieties (2). The three-line hybrid rice breeding system was developed in the 1970s after the revolutionary discovery of the wild abortive cytoplasmic male sterile cytoplasm (CMS-WA) for the breeding of CMS lines, which solved the problem of selfpollination in the varieties used for hybrid rice production (3). In this technology, a restorer line that contains the restorer gene(s) is used as the pollen donor to recover male fertility in F 1 plants (hybrid rice) after its cross with the CMS line (Fig. S1A). To maintain CMS, a maintainer line, which has viable pollen grains and normal seed sets, is used as the pollinator to cross with the CMS line (Fig. S1A). Although this system has been widely used for hybrid rice seed production, the requirement of a maintainer line with normal cytoplasm and a restorer line with nuclearencoded fertility restorer genes restricts breeders from exploiting more rice germplasms and complicates the procedures for generating hybrid seeds (4).As a replacement of the three-line technology, a two-line system has been developed and applied for hybrid rice seed production after the discovery of the environmentally sensitive genic male sterile lines controlled by nuclear recessive gene(s). A japonica cultivar, Nongken 58S (NK58S), was the first spontaneous photoperiod-sensitive genic male sterile (PGMS) mutant identified (5). Because indica varieties are predominant in most rice planting regions, the PGMS loci/locus in NK58S were/was introduced into indica to generate breeding cultivars, such as Peiai 64S (PA64S) and Xin'an S. These ...

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