Natural variation in CRABS CLAW contributes to fruit length divergence in cucumber.

Fruit length is a key domestication trait that affects crop yield and appearance. Cucumber (Cucumis sativus) fruits vary from 5 to 60 cm in length. Despite the identification of several regulators and multiple quantitative trait loci (QTLs) underlying fruit length, the natural variation, and molecular mechanisms underlying differences in fruit length are poorly understood. Through map-based cloning, we identified a nonsynonymous polymorphism (G to A) in CRABS CLAW (CsCRC) as underlying the major-effect fruit size/shape QTL FS5.2 in cucumber. The short-fruit allele CsCRCA is a rare allele that has only been found in round-fruited semi-wild Xishuangbanna cucumbers. A near-isogenic line (NIL) homozygous for CsCRCA exhibited a 34∼39% reduction in fruit length. Introducing CsCRCG into this NIL rescued the short-fruit phenotype, and knockdown of CsCRCG resulted in shorter fruit and smaller cells. In natural cucumber populations, CsCRCG expression was positively correlated with fruit length. Further, CsCRCG, but not CsCRCA, targets the downstream auxin-responsive protein gene CsARP1 to regulate its expression. Knockout of CsARP1 produced shorter fruit with smaller cells. Hence, our work suggests that CsCRCG positively regulates fruit elongation through transcriptional activation of CsARP1 and thus enhances cell expansion. Using different CsCRC alleles provides a strategy to manipulate fruit length in cucumber breeding.

Phytochrome-interacting factor PIF3 integrates phytochrome B and UV-B signaling pathways to regulate gibberellin- and auxin-dependent growth in cucumber hypocotyls.

In Arabidopsis, the photoreceptors phytochrome B (PhyB) and UV-B resistance 8 (UVR8) mediate light responses that play a major role in regulating photomorphogenic hypocotyl growth, but how they crosstalk to coordinate this process is not well understood. Here we report map-based cloning and functional characterization of an ultraviolet (UV)-B-insensitive, long-hypocotyl mutant, lh1, and a wild-type-like mutant, lh2, in cucumber (Cucumis sativus), which show defective CsPhyB and GA oxidase2 (CsGA20ox-2), a key gibberellic acid (GA) biosynthesis enzyme, respectively. The lh2 mutation was epistatic to lh1 and partly suppressed the long-hypocotyl phenotype in the lh1lh2 double mutant. We identified phytochrome interacting factor (PIF) CsPIF3 as playing a critical role in integrating the red/far-red and UV-B light responses for hypocotyl growth. We show that two modules, CsPhyB-CsPIF3-CsGA20ox-2-DELLA and CsPIF3-auxin response factor 18 (CsARF18), mediate CsPhyB-regulated hypocotyl elongation through GA and auxin pathways, respectively, in which CsPIF3 binds to the G/E-box motifs in the promoters of CsGA20ox-2 and CsARF18 to regulate their expression. We also identified a new physical interaction between CsPIF3 and CsUVR8 mediating CsPhyB-dependent, UV-B-induced hypocotyl growth inhibition. Our work suggests that hypocotyl growth in cucumber involves a complex interplay of multiple photoreceptor- and phytohormone-mediated signaling pathways that show both conservation with and divergence from those in Arabidopsis.

An LTR retrotransposon insertion inside CsERECTA for an LRR receptor-like serine/threonine-protein kinase results in compact (cp) plant architecture in cucumber.

The compact (cp) phenotype in cucumber (Cucumis sativus L.) is an important plant architecture-related trait with a great potential for cucumber improvement. In this study, we conducted map-based cloning of the cp locus, identified and functionally characterized the candidate gene. Comparative microscopic analysis suggested that the short internode in the cp mutant is due to fewer cell numbers. Fine genetic mapping delimited cp into an 8.8-kb region on chromosome 4 harboring only one gene, CsERECTA (CsER) that encodes a leucine-rich repeat receptor-like kinase. A 5.5-kb insertion of a long terminal repeat retrotransposon in the 22nd exon resulted in loss-of-function of CsER in the cp plant. Spatiotemporal expression analysis in cucumber and CsER promoter-driven GUS assays in Arabidopsis indicated that CsER was highly expressed in the stem apical meristem and young organs, but the expression level was similar in the wild type and mutant cucumber plants. However, CsER protein accumulation was reduced in the mutant as revealed by western hybridization. The mutation in cp also did not seem to affect self-association of CsER for formation of dimers. Ectopic expression of CsER in Arabidopsis was able to rescue the plant height of the loss-of-function AtERECTA mutant, whereas the compact inflorescence and small rosette leaves of the mutant could be partially recovered. Transcriptome profiling in the mutant and wild type cucumber plants revealed hormone biosynthesis/signaling, and photosynthesis pathways associated with CsER-dependent regulatory network. Our work provides new insights for the use of cp in cucumber breeding.

A Functional Allele of CsFUL1 Regulates Fruit Length through Repressing CsSUP and Inhibiting Auxin Transport in Cucumber.

Fruit length is a prominent agricultural trait during cucumber (Cucumis sativus) domestication and diversifying selection; however, the regulatory mechanisms of fruit elongation remain elusive. We identified two alleles of the FRUITFULL (FUL)-like MADS-box gene CsFUL1 with 3393C/A Single Nucleotide Polymorphism variation among 150 cucumber lines. Whereas CsFUL1A was specifically enriched in the long-fruited East Asian type cucumbers (China and Japan), the CsFUL1C allele was randomly distributed in cucumber populations, including wild and semiwild cucumbers. CsFUL1A knockdown led to further fruit elongation in cucumber, whereas elevated expression of CsFUL1A resulted in significantly shorter fruits. No effect on fruit elongation was detected when CsFUL1C expression was modulated, suggesting that CsFUL1A is a gain-of-function allele in long-fruited cucumber that acts as a repressor during diversifying selection of East Asian cucumbers. Furthermore, CsFUL1A binds to the CArG-box in the promoter region of SUPERMAN, a regulator of cell division and expansion, to repress its expression. Additionally, CsFUL1A inhibits the expression of auxin transporters PIN-FORMED1 (PIN1) and PIN7, resulting in decreases in auxin accumulation in fruits. Together, our work identifies an agriculturally important allele and suggests a strategy for manipulating fruit length in cucumber breeding that involves modulation of CsFUL1A expression.

Phenotypic Characterization and Fine Mapping of a Major-Effect Fruit Shape QTL FS5.2 in Cucumber, Cucumis sativus L., with Near-Isogenic Line-Derived Segregating Populations.

Cucumber (Cucumis sativus L.) fruit size/shape (FS) is an important yield and quality trait that is quantitatively inherited. Many quantitative trait loci (QTLs) for fruit size/shape have been identified, but very few have been fine-mapped or cloned. In this study, through marker-assisted foreground and background selections, we developed near-isogenic lines (NILs) for a major-effect fruit size/shape QTL FS5.2 in cucumber. Morphological and microscopic characterization of NILs suggests that the allele of fs5.2 from the semi-wild Xishuangbanna (XIS) cucumber (C. s. var. xishuangbannesis) reduces fruit elongation but promotes radial growth resulting in shorter but wider fruit, which seems to be due to reduced cell length, but increased cellular layers. Consistent with this, the NIL carrying the homozygous XIS allele (fs5.2) had lower auxin/IAA contents in both the ovary and the developing fruit. Fine genetic mapping with NIL-derived segregating populations placed FS5.2 into a 95.5 kb region with 15 predicted genes, and a homolog of the Arabidopsis CRABS CLAW (CsCRC) appeared to be the most possible candidate for FS5.2. Transcriptome profiling of NIL fruits at anthesis identified differentially expressed genes enriched in the auxin biosynthesis and signaling pathways, as well as genes involved in cell cycle, division, and cell wall processes. We conclude that the major-effect QTL FS5.2 controls cucumber fruit size/shape through regulating auxin-mediated cell division and expansion for the lateral and longitudinal fruit growth, respectively. The gibberellic acid (GA) signaling pathway also plays a role in FS5.2-mediated fruit elongation.

Recent Progress in Biosensors for Detection of Tumor Biomarkers.

Cancer is a leading cause of death worldwide, with an increasing mortality rate over the past years. The early detection of cancer contributes to early diagnosis and subsequent treatment. How to detect early cancer has become one of the hot research directions of cancer. Tumor biomarkers, biochemical parameters for reflecting cancer occurrence and progression have caused much attention in cancer early detection. Due to high sensitivity, convenience and low cost, biosensors have been largely developed to detect tumor biomarkers. This review describes the application of various biosensors in detecting tumor markers. Firstly, several typical tumor makers, such as neuron-specific enolase (NSE), carcinoembryonic antigen (CEA), prostate-specific antigen (PSA), squamous cell carcinoma antigen (SCCA), carbohydrate, antigen19-9 (CA19-9) and tumor suppressor p53 (TP53), which may be helpful for early cancer detection in the clinic, are briefly described. Then, various biosensors, mainly focusing on electrochemical biosensors, optical biosensors, photoelectrochemical biosensors, piezoelectric biosensors and aptamer sensors, are discussed. Specifically, the operation principles of biosensors, nanomaterials used in biosensors and the application of biosensors in tumor marker detection have been comprehensively reviewed and provided. Lastly, the challenges and prospects for developing effective biosensors for early cancer diagnosis are discussed.

Structural analysis of transient reaction intermediate in formic acid dehydrogenation catalysis using two-dimensional IR spectroscopy.

The molecular structure of a catalytically active key intermediate is determined in solution by employing 2D IR spectroscopy measuring vibrational cross-angles. The formate intermediate (2) in the formic acid dehydrogenation reaction catalyzed by a phosphorus-nitrogen PN3P-Ru catalyst is elucidated. Our spectroscopic studies show that the complex features a formate ion directly attached to the Ru center as a ligand, and a proton added to the imine arm of the dearomatized PN3P* ligand. During the catalytic process, the imine arms are not only reversibly protonated and deprotonated, but also interacting with the protic substrate molecules, effectively serving as the local proton buffer to offer remarkable stability with a turnover number (TON) over one million.

Genome-Wide Identification and Characterization of KNOTTED-Like Homeobox (KNOX) Homologs in Garlic (Allium sativum L.) and Their Expression Profilings Responding to Exogenous Cytokinin and Gibberellin.

Garlic (Allium sativum L.) is an important vegetable and is cultivated and consumed worldwide for its economic and medicinal values. Garlic cloves, the major reproductive and edible organs, are derived from the axillary meristems. KNOTTED-like homeobox (KNOX) proteins, such as SHOOT MERISTEM-LESS (STM), play important roles in axillary meristem formation and development. However, the KNOX proteins in garlic are still poorly known. Here, 10 AsKNOX genes, scattered on 5 of the 8 chromosomes, were genome-wide identified and characterized based on the newly released garlic genome. The typical conserved domains of KNOX proteins were owned by all these 10 AsKNOX homologs, which were divided into two Classes (Class I and Class II) based on the phylogenetic analysis. Prediction and verification of the subcellular localizations revealed the diverse subcellular localization of these 10 AsKNOX proteins. Cis-element prediction, tissue expression analysis, and expression profilings in responding to exogenous GA3 and 6-BA showed the potential involvement of AsKNOX genes in the gibberellin and cytokinin signaling pathways. Overall, the results of this work provided a better understanding of AsKNOX genes in garlic and laid an important foundation for their further functional studies.

Garlic Volatile Diallyl Disulfide Induced Cucumber Resistance to Downy Mildew.

Allicin compositions in garlic are used widely as fungicides in modern agriculture, in which diallyl disulfide (DADS) is a major compound. Downy mildew, caused by Pseudoperonospora cubensis (P. cubensis), is one of the most destructive diseases and causes severe yield losses in cucumbers. To explore the potential mechanism of DADS-induced cucumber resistance to downy mildew, cucumber seedlings were treated with DADS and then inoculated with P. cubensis at a 10-day interval. Symptom observation showed that DADS significantly induced cucumber resistance to downy mildew. Furthermore, both lignin and H2O2 were significantly increased by DADS treatment to responding P. cubensis infection. Simultaneously, the enzyme activities of peroxidase (POD) in DADS-treated seedlings were significantly promoted. Meanwhile, both the auxin (IAA) and salicylic acid (SA) contents were increased, and their related differentially expressed genes (DEGs) were up-regulated when treated with DADS. Transcriptome profiling showed that many DEGs were involved in the biological processes of defense responses, in which DEGs on the pathways of 'phenylpropanoid biosynthesis', 'phenylalanine metabolism', 'MAPK signaling', and 'plant hormone signal transduction' were significantly up-regulated in DADS-treated cucumbers uninoculated with the pathogen. Based on the results of several physiological indices and transcriptomes, a potential molecular mechanism of DADS-induced cucumber resistance to downy mildew was proposed and discussed. The results of this study might give new insight into the exploration of the induced resistance mechanism of cucumber to downy mildew and provide useful information for the subsequent mining of resistance genes in cucumber.

QTL for horticulturally important traits associated with pleiotropic andromonoecy and carpel number loci, and a paracentric inversion in cucumber.

The legendary cucumber inbred line WI2757 possesses a rare combination of resistances against nine pathogens, which is an important germplasm for cucumber breeding. However, WI2757 flowers late and does not perform well under field conditions. The genetic basis for horticulturally important traits other than disease resistances in WI2757 is largely unknown. In this study, we conducted QTL mapping using F2 and recombinant inbred line (RIL) populations from the WI2757 × True Lemon cross that were segregating for multiple traits. Phenotypic data were collected in replicated field trials across multiple years for seven traits including fruit carpel number (CN) and sex expression. A high-density SNP-based genetic map was developed with genotyping by sequencing of the RIL population, which revealed a region on chromosome 1 with strong recombination suppression. The reduced recombination in this region was due to a ~ 10-Mbp paracentric inversion in WI2757 that was confirmed with additional segregation and cytological (FISH) analyses. Thirty-six QTL were detected for flowering time, fruit length (FL), fruit diameter (FD), fruit shape (LD), fruit number (FN), CN, and powdery mildew resistance. Five moderate- or major-effect QTL for FL, FD, LD, and FN inside the inversion are likely the pleiotropic effects of the andromonoecy (m), or the cn locus. The major-effect flowering time QTL ft1.1 was also mapped inside the inversion, which seems to be different from the previously assigned delayed flowering in WI2757. Implications of these findings on the use of WI2757 in cucumber breeding are discussed.

Genetic architecture of fruit size and shape variation in cucurbits: a comparative perspective.

The Cucurbitaceae family hosts many economically important fruit vegetables (cucurbits) such as cucumber, melon, watermelon, pumpkin/squash, and various gourds. The cucurbits are probably best known for the diverse fruit sizes and shapes, but little is known about their genetic basis and molecular regulation. Here, we reviewed the literature on fruit size (FS), shape (FSI), and fruit weight (FW) QTL identified in cucumber, melon, and watermelon, from which 150 consensus QTL for these traits were inferred. Genome-wide survey of the three cucurbit genomes identified 253 homologs of eight classes of fruit or grain size/weight-related genes cloned in Arabidopsis, tomato, and rice that encode proteins containing the characteristic CNR (cell number regulator), CSR (cell size regulator), CYP78A (cytochrome P450), SUN, OVATE, TRM (TONNEAU1 Recruiting Motif), YABBY, and WOX domains. Alignment of the consensus QTL with candidate gene homologs revealed widespread structure and function conservation of fruit size/shape gene homologs in cucurbits, which was exemplified with the fruit size/shape candidate genes CsSUN25-26-27a and CsTRM5 in cucumber, CmOFP1a in melon, and ClSUN25-26-27a in watermelon. In cucurbits, the andromonoecy (for 1-aminocyclopropane-1-carboxylate synthase) and the carpel number (for CLAVATA3) loci are known to have pleiotropic effects on fruit shape, which may complicate identification of fruit size/shape candidate genes in these regions. The present work illustrates the power of comparative analysis in understanding the genetic architecture of fruit size/shape variation, which may facilitate QTL mapping and cloning for fruit size-related traits in cucurbits. The limitations and perspectives of this approach are also discussed.

Three Cases of Karoshi Without the Typical Pathomorphological Features of Cardiovascular/Cerebrovascular Disease.

Karoshi is a term used to describe unexplained sudden death associated with overwork and has become a serious public health issue in China. Cases have occurred in physicians, university professors, engineers in high-tech companies, and blue-collar workers. The mechanisms associated with death by overwork are very complex. According to most researchers, karoshi is considered to be caused by an excessive workload that induces deterioration of underlying hypertension or atherosclerosis. These conditions inevitably lead to death from cardiovascular or cerebrovascular diseases. However, in our own experience, we have found that in some cases, the victims of karoshi were in a chronic state of overwork but without a history of cardiovascular or cerebrovascular diseases. In support of this, we have found that even autopsies have revealed few positive findings except for cardiac hypertrophy. In this article, we report 3 typical cases of karoshi but without the typical pathomorphological features of cardiovascular or cerebrovascular disease.

LITTLELEAF (LL) encodes a WD40 repeat domain-containing protein associated with organ size variation in cucumber.

Plants employ tight genetic control to integrate intrinsic growth signals and environmental cues to enable organs to grow to a defined size. Many genes contributing to cell proliferation and/or cell expansion, and consequently organ size control, have been identified, but the regulatory pathways are poorly understood. Here we have characterized a cucumber littleleaf (ll) mutant which exhibits smaller organ sizes but more lateral branches than the wild type. The small organ size in ll was due to a reduction of both cell number and cell size. Quantitative trait locus (QTL) analyses revealed co-localization of major-effect QTLs for fruit size, fruit and seed weight, as well as number of lateral branches, with the LL locus indicating pleiotropic effects of the ll mutation. We demonstrate that LL is an ortholog of Arabidopsis STERILE APETALA (SAP) encoding a WD40 repeat domain-containing protein; the mutant protein differed from the wild type by a single amino acid substitution (W264G) in the second WD40 repeat. W264 was conserved in 34 vascular plant genomes examined. Phylogenetic analysis suggested that LL originated before the emergence of flowering plants but was lost in the grass genome lineage. The function of LL in organ size control was confirmed by its overexpression in transgenic cucumbers and ectopic expression in Arabidopsis. Transcriptome profiling in LL and ll bulks revealed a complex regulatory network for LL-mediated organ size variation that involves several known organ size regulators and associated pathways. The data support LL as an important player in organ size control and lateral branch development in cucumber.

I2-DMSO-H2O: A Metal-Free Combination System for the Oxidative Addition of Alkynes to Access (E)-α-Iodo-ß-methylsulfonylalkenes.

A simple and green reaction was discovered for iodization-methylsulfoxidation of alkynes to access (E)-α-iodo-ß-methylsulfonylalkenes. This is the first report for the synthesis of iodovinyl methylsulfones by employing alkynes to react with molecular iodine (I2), dimethyl sulfoxide (DMSO), and H2O. Additionally, this protocol represents a new avenue for utilizing DMSO as the source of the -SO2Me group and H2O as the "O" source for the construction of the -SO2Me group from DMSO, which is a valuable finding.

The WUSCHEL-related homeobox1 gene of cucumber regulates reproductive organ development.

The WUSCHEL-related homeobox1 (WOX1) transcription factor plays an important role in lateral growth of plant organs; however, the underlying mechanisms in the regulation of reproductive development are largely unknown. Cucumber (Cucumis sativus) has separate male and female flowers, facilitating the study of the role of WOX1 in stamen and carpel development. Here, we identified a mango fruit (mf) mutant in cucumber, which displayed multiple defects in flower growth as well as male and female sterility. Map-based cloning showed that Mf encodes a WOX1-type transcriptional regulator (CsWOX1), and that the mf mutant encodes a truncated protein lacking the conserved WUS box. Further analysis showed that elevated expression of CsWOX1 was responsible for the mutant phenotype in cucumber and Arabidopsis. Comparative transcriptome profiling revealed certain key players and CsWOX1-associated networks that regulate reproductive development. CsWOX1 directly interacts with cucumber SPOROCYTELESS (CsSPL), and many genes in the CsSPL-mediated pathway were down-regulated in plants with the mutant allele at the Mf locus. In addition, auxin distribution was affected in both male and female flowers of the mutant. Taking together, these data suggest that CsWOX1 may regulate early reproductive organ development and be involved in sporogenesis via the CsSPL-mediated pathway and/or modulate auxin signaling in cucumber.

SHORT HYPOCOTYL1 Encodes a SMARCA3-Like Chromatin Remodeling Factor Regulating Elongation.

In Arabidopsis (Arabidopsis thaliana), the UVR8-mediated signaling pathway is employed to attain UVB protection and acclimation to deal with low-dosage UVB (LDUVB)-induced stresses. Here, we identified SHORT HYPOCOTYL1 (SH1) in cucumber (Cucumis sativus), which regulates LDUVB-dependent hypocotyl elongation by modulating the UVR8 signaling pathway. We showed that hypocotyl elongation in cucumbers carrying the recessive sh1 allele was LDUVB insensitive and that Sh1 encoded a human SMARCA3-like chromatin remodeling factor. The allele frequency and distribution pattern at this locus among natural populations supported the wild cucumber origin of sh1 for local adaptation, which was under selection during domestication. The cultivated cucumber carries predominantly the Sh1 allele; the sh1 allele is nearly fixed in the semiwild Xishuangbanna cucumber, and the wild cucumber population is largely at Hardy-Weinberg equilibrium for the two alleles. The SH1 protein sequence was highly conserved among eukaryotic organisms, but its regulation of hypocotyl elongation in cucumber seems to be a novel function. While Sh1 expression was inhibited by LDUVB, its transcript abundance was highly correlated with hypocotyl elongation rate and the expression level of cell-elongation-related genes. Expression profiling of key regulators in the UVR8 signaling pathway revealed significant differential expression of CsHY5 between two near isogenic lines of Sh1 Sh1 and CsHY5 acted antagonistically at transcriptional level. A working model was proposed in which Sh1 regulates LDUVB-dependent hypocotyl elongation in cucumber through changing the chromatin states and thus the accessibility of CsHY5 in the UVR8 signaling pathway to promoters of LDUVB-responsive genes for hypocotyl elongation.

QTL mapping of domestication and diversifying selection related traits in round-fruited semi-wild Xishuangbanna cucumber (Cucumis sativus L. var. xishuangbannanesis).

KEY MESSAGE: QTL analysis revealed 11 QTL underlying flowering time and fruit size variation in the semi-wild Xishuangbanna cucumber, of which, FT6.2 and FS5.2 played the most important roles in determining photoperiod-dependent flowering time and round-fruit shape, respectively. Flowering time and fruit size are two important traits in domestication and diversifying selection in cucumber, but their genetic basis is not well understood. Here we reported QTL mapping results on flowering time and fruit size with F2 and F2:3 segregating populations derived from the cross between WI7200, a small fruited, early flowering primitive cultivated cucumber and WI7167, a round-fruited, later flowering semi-wild Xishuangbanna (XIS) cucumber. A linkage map with 267 microsatellite marker loci was developed with 138 F2 plants. Phenotypic data of male and female flowering time, fruit length and diameter and three other traits (mature fruit weight and number, and seedling hypocotyl length) were collected in multiple environments. Three flowering time QTL, FT1.1, FT5.1 and FT6.2 were identified, in which FT6.2 played the most important role in conferring less photoperiod sensitive early flowering during domestication whereas FT1.1 seemed more influential in regulating flowering time within the cultivated cucumber. Eight consensus fruit size QTL distributed in 7 chromosomes were detected, each of which contributed to both longitudinal and radial growth in cucumber fruit development. Among them, FS5.2 on chromosome 5 exhibited the largest effect on the determination of round fruit shape that was characteristic of the WI7167 XIS cucumber. Possible roles of these flowering time and fruit size QTL in domestication of cucumber and crop evolution of the semi-wild XIS cucumber, as well as the genetic basis of round fruit shape in cucumber are discussed.

Round fruit shape in WI7239 cucumber is controlled by two interacting quantitative trait loci with one putatively encoding a tomato SUN homolog.

KEY MESSAGE: QTL analysis revealed two interacting loci, FS1.2 and FS2.1, underlying round fruit shape in WI7239 cucumber; CsSUN , a homolog of tomato fruit shape gene SUN , was a candidate for FS1.2. Fruit size is an important quality and yield trait in cucumber, but its genetic basis remains poorly understood. Here we reported QTL mapping results on fruit size with segregating populations derived from the cross between WI7238 (long fruit) and WI7239 (round fruit) inbred cucumber lines. Phenotypic data of fruit length and diameter were collected at anthesis, immature and mature fruit stages in four environments. Ten major-effect QTL were detected for six traits; synthesis of information from these QTL supported two genes, FS1.2 and FS2.1, underlying fruit size variation in the examined populations. Under the two-gene model, deviation from expected segregation ratio in fruit length and diameter among segregating populations was observed, which could be explained mainly by the interactions between FS1.2 and FS2.1, and segregation distortion in the FS2.1 region. Genome-wide candidate gene search identified CsSUN, a homolog of the tomato fruit shape gene SUN, as the candidate for FS1.2. The round-fruited WI7239 had a 161-bp deletion in the first exon of CsSUN, and its expression in WI7239 was significantly lower than that in WI7238. A marker derived from this deletion was mapped at the peak location of FS1.2 in QTL analysis. Comparative analysis suggested the melon gene CmSUN-14, a homolog of CsSUN as a candidate of the fl2/fd2/fw2 QTL in melon. This study revealed the unique genetic architecture of round fruit shape in WI7239 cucumber. It also highlights the power of QTL analysis for traits with a simple genetic basis but their expression is complicated by other factors.

Fine mapping identifies CsGCN5 encoding a histone acetyltransferase as putative candidate gene for tendril-less1 mutation (td-1) in cucumber.

KEY MESSAGE: Next-generation sequencing-aided map-based cloning delimited the cucumber tendril - less1 ( td - 1 ) locus into a 190.7-kb region in chromosome 6 harboring a putative, novel-function candidate gene encoding a histone acetyltransferase ( CsGCN5 ). The tendril initiated from the lateral meristem is an important and characteristic organ for the species in the Cucurbitaceae family including cucumber (Cucumis sativus L.). While the tendril has its evolutionary significance, it also poses a nuisance in cucumber cultivation under protected environments in which tendril-less cucumber has its advantages. From an EMS mutagenesis population, we identified a tendril-less mutant B007, which was controlled by a recessive gene td-1. Through next-generation sequencing-aided map-based cloning, we show CsGCN5 (Cucumis sativus GENERAL CONTROL NONDEREPRESSIBLE 5), a cucumber gene for a histone acetyltransferase as the most possible candidate for td-1. A non-synonymous SNP in the first exon of CsGCN5 resulted in an amino-acid substitution from Asp (D) in the wild type to Asn (N) in the tendril-less mutant. The candidacy of CsGCN5 was further confirmed by multiple lines of evidence in both biparental and natural cucumber populations. Non-significant expression of CsGCN5 in multiple organs was found between the wild type and the mutant. CsGCN5 exhibited strong expression in the tendril of wild-type plants suggesting its important roles in growth and development of plant tendrils. The identification and characterization of the td-1 mutant from the present study provided a useful tool in understanding the molecular mechanisms of tendril organogenesis and investigation of novel functions of the histone acetyltransferase in cucumber.

Dehydrogenation of Formic Acid Catalyzed by a Ruthenium Complex with an N,N'-Diimine Ligand.

We report a ruthenium complex containing an N,N'-diimine ligand for the selective decomposition of formic acid to H2 and CO2 in water in the absence of any organic additives. A turnover frequency of 12 000 h-1 and a turnover number of 350 000 at 90 °C were achieved in the HCOOH/HCOONa aqueous solution. Efficient production of high-pressure H2 and CO2 (24.0 MPa (3480 psi)) was achieved through the decomposition of formic acid with no formation of CO. Mechanistic studies by NMR and DFT calculations indicate that there may be two competitive pathways for the key hydride transfer rate-determining step in the catalytic process.