How Do Stomata Sense Reductions in Atmospheric Relative Humidity？

Dear Editor, It has been known since the work of Francis Darwin that, in response to a reduction in atmospheric relative humidity （rh）, stomatal aperture decreases. Screening for Arabidopsis mutants compromised in stomatal responses to reduced rh resulted in the identification of two genes, OST1 and ABA2, that are involved in stomatal response to low rh conditions. Interestingly both encode proteins previously known to be involved in ABA signaling （Xie et al., 2006, and references therein）. These findings strongly suggested that, at least in part, the stomatal response to low rh is mediated by ABA and the intracellular ABA signaling pathway. Our most recent data show that low rh-induced stomatal closure can pro- ceed by guard cell autonomous ABA synthesis （Bauer et al., 2013）,     

Riboflavin-induced Priming for Pathogen Defense in Arabidopsis thaliana

Riboflavin （vitamin B2） participates in a variety of redox processes that affect plant defense responses. Previously we have shown that riboflavin induces pathogen resistance in the absence of hypersensitive cell death （HCD） in plants. Herein, we report that riboflavin induces priming of defense responses in Arabidopsis thaliana toward infection by virulent Pseudomonas syringae pv. tomato DC3000 （Pst）. Induced resistance was mechanistically connected with the expression of defense response genes and cellular defense events, including H202 burst, HCD, and callose deposition in the plant. Riboflavin treatment and inoculation of plants with Pst were neither active but both synergized to induce defense responses. The priming process needed NPRI （essential regulator of systemic acquired resistance） and maintenance of H202 burst but was independent of salicylic acid, jasmonic acid, ethylene, and abscisic acid. Our results suggest that the role of riboflavin in priming defenses is subject to a signaling process distinct from the known pathways of hormone signal transduction.     

Dihydroactinidiolide,a High Light-Induced 13-Carotene Derivative that Can Regulate Gene Expression and Photoacclimation in Arabidopsis

Dear Editor,
The physiological functions of carotenoids in plants go beyond their traditional roles as accessory light-har- vesting pigments, natural colorants, and quenchers of tri- plet chlorophyll and singlet oxygen （102）. Recent studies have indeed emphasized the functional role of molecules derived from carotenoids as phytohormones （Ruyter-Spira et al., 20β） or messengers in stress signaling pathways （Havaux, 2014）. In particular, chemical quenching of 102 by carotenoids within the photosystems involves oxidation of the carotenoid molecules, generating a variety of oxi- dized products （Ramel et al., 2012）. β-Cyclocitral, a volatile C7 derivative of β-carotene, is one such molecule produced during high light stress, which was found to induce changes in the expression of 102-responsive genes （Ramel et al., 2012）. Moreover, the β-cyclocitral-dependent gene repro- gramming was associated with an increased tolerance of the plants to photooxidative stress. These effects appeared to be specific to β-cyclocitral since they were not observed with β-ionone, a C9-oxidized derivative of ~-carotene, which was not able to induce or repress the expression of 1O2 gene markers. Based on those results, it was pro- posed that β-cyclocitral is a plastid messenger involved in the chloroplast-to-nucleus 1O2 signaling pathway lead- ing to acclimation to high light stress （Ramel et al., 2012）. However, in vitro 102 oxidation of β-carotene is known to produce other volatile compounds besides β-cyclocitral and IB-ionone, such as dihydroactinidiolide （dhA, Figure 1A） and a-ionene （Ramel et al., 2012）. The dhA molecule is a lac- tone （cyclic ester） resulting from the secondary oxidation of β-ionone through the intermediate 5,6-epoxy-β-ionone （Havaux, 2014）. Both dhA and o-ionene were detected in plant leaves and fruits （e.g. Del Mar Caja et al., 2009; Ramel et al., 2012）. Interestingly, dhA, but not o-ionene, was reported to accumulate in Arabidopsis leaves under hiclh liclht str     

A Brassinosteroid-Signaling Kinase Interacts withMultiple Receptor-Like Kinases in Arabidopsis

Dear Editor, Higher plants have evolved hundreds of genes encodingreceptor-like kinases （RLKs）, which function as cell surfacereceptors perceiving developmental and environmental sig-nals （Shiu et al., 2004）. Many RLKs have been shown to playspecific roles in hormone responses, developmental regula-tion, defense against pathogen infection, and adaptationto abiotic stresses （Chae et al., 2009; Antolin-Llovera et al.,2012）. The mechanisms that ensure specific signal transduc-tion from each RLK to target cellular responses remain poorlyunderstood. Recent studies revealed that many RLKs trans-duce signals by phosphorylating receptor-like cytoplasmickinases （RLCKs）, which lack the transmembrane domainsbut are anchored at the plasma membrane through lipidmodification （Tang et al., 2008; Zhang et al., 2010; Shi et al.,2013）. There are over 400 RLKs and only about 150 RLCKs inArabidopsis （Shiu et al., 2004）. One outstanding question iswhether each RLCK mediates signaling downstream of a spe-cific RLK, participates in multiple RLK pathways, or mediatescrosstalk between RLK pathways.     

Hydrogen Peroxide in Plants： a Versatile Molecule of the Reactive Oxygen Species Network

Plants often face the challenge of severe environmental conditions, which include various biotic and abiotic stresses that exert adverse effects on plant growth and development. During evolution, plants have evolved complex regulatory mechanisms to adapt to various environmental stressors. One of the consequences of stress is an increase in the cellular concentration of reactive oxygen species （ROS）, which are subsequently converted to hydrogen peroxide （H2O2）. Even under normal conditions, higher plants produce ROS during metabolic processes. Excess concentrations of ROS result in oxidative damage to or the apoptotic death of cells. Development of an antioxidant defense system in plants protects them against oxidative stress damage. These ROS and, more particularly, H2O2, play versatile roles in normal plant physiological processes and in resistance to stresses. Recently, H2O2 has been regarded as a signaling molecule and regulator of the expression of some genes in cells. This review describes various aspects of H2O2 function, generation and scavenging, gene regulation and cross-links with other physiological molecules during plant growth, development and resistance responses.     

A Start Point for Extracellular Nucleotide Signaling

A START POINT FOR EXTRACELLULAR NUCLEOTIDE SIGNALING
The recent discovery of a plant receptor for extracellu- lar nucleotides, reported by Choi et al. （2014）, is a major breakthrough that had been anticipated for over a dec- ade. Plants release ATP into their extracellular matrix （ECM） during growth and when they are induced by vari- ous biotic and abiotic stimuli （Clark and Roux, 2011）. That these extracellular nucleotides would activate receptors in plants was predicted by two sets of discoveries： that low- and sub-micromolar ATP could induce increases in [Ca2＋]cyt, NO, and superoxide signaling intermediates that led to downstream growth, stomatal, and defense responses, and that these changes could be blocked by antagonists that blocked extracellular nucleotide receptors in animals （Demidchik et al., 2003; Song et al., 2006; Clark et al., 2011; Demidchik et al., 2009, 2011）. Although mammalian biolo- gists had discovered two classes of receptors for extracel- lular nucleotides （P2X and P2Y） decades ago （Burnstock, 2007）, there were no plant proteins obviously similar to these in any sequence data available. Clearly, if there were plant purinoceptors, they would be different from the mammalian receptors, and they could not be discovered by motif searches.     

Characterization and Molecular Mapping of a New Virescent Mutant in Rice

Plant leaves play a significant role in photosynthesis. Normal chloroplast development is critical for plant growth and yield performance. Defect of the chlorophyll in chloroplasts may cause abnormal leaf colors, such as yellow, white, or stripe. Chloroplasts have their own genomes encoding for about 100 genes that are essential for plastid protein synthesis and photosynthesis （Kanno and Hirai, 1993; Sato et al., 1999）. Moreover, over 3000 proteins encoded by plant nuclear genomes target to the chloroplasts and participate in the chloroplast development and/or photosynthesis. Hitherto, a number of plant genes, which encode for enzymes involved in chlorophyll biosynthetic pathways,     

Intracellular NHX-Type Cation/H＋ Antiporters inPlants

Cells depend on the homeostatic maintenance of pHwithin specific cellular compartments to ensure optimalconditions for metabolic and enzymatic processes as wellas protein structure and function. In the animal secre-tory pathway, cells maintain distinct luminal pHs withinvarious compartments （Paroutis et al., 2004）. Among themany molecular players that contribute to pH and ionhomeostasis in plants, Na＋（K＋）/H＋ exchangers （also knownas NHX-type cation/H＋ antiporters） appear to be particu-larly important for the regulation of a wide variety ofphysiological processes, including cell expansion, cellvolume regulation, osmotic adjustment, pH regulation,membrane trafficking, protein processing, and cellularstress responses （Pardo et al., 2006; Rodriguez-Rosaleset al., 2009; Bassil et al., 2012）. In plants, NHX antiportersappeared early in evolution and are ubiquitously encodedmembers of the CPA1 cation/H＋ antiporters subgroupthat belongs to the large family of monovalent cation/H＋ transporters CPA （Brett et al., 2005）. NHX antiport-ers are found, thus far, in all sequenced plant genomes（Bassil et al., 2012; Chanroj et al., 2012）. In Arabidopsis,the NHX family consists of eight isoforms, six of whichare intracellular （AtNHXl-AtNHX6）, located either to thevacuole （AtNHXl to AtNHX4） or endosomes （AtNHX5 andAtNHX6） and an additional two more divergent members（AtNHX7/SOSl and AtNHX8） at the plasma membrane（Bassil et al., 2012）. Orthologous sequences in each of thethree classes （plasma membrane, vacuolar, or endosomal）appear in all sequenced genomes, suggesting that distinctfunctional NHX classes appeared early in evolution andmay have conserved roles that are compartment-specific（Bassil et al., 2012）. Emerging new evidence highlightsthe importance of particular intracellular NHX antiport-ers in the regulation of vesicular and vacuolar pH andK＋ homeostasis. Vacuolar NHXs are needed to maintainK＋ homeostasis between the vacuole and cytosol, with-out which cell expansion is compromised （Bassil et al.,2011b）. Other NHX isoforms （endosomal） are requiredfor membrane trafficking and raise interesting new ques-tions about the role of pH and ion homeostasis in proteinprocessing and trafficking in the endomembrane system（Bassil et al., 2011a）. In this update, we aim to highlightrecent new evidence on intracellular NHX antiportersand emphasize possible novel and important cellular pro-cesses regulated by this particularly interesting group oftransporters.     

What can we Learn from Oxygen and Hydrogen Isotope Compositions of Tree-ring Cellulose in Higher Plants (英文)

Stable isotope ratios in tree-ring cellulose have been shown to be reliable recorders of changes in the ambient climate (Leuenberger et al., 1998). Thus, isotopic fractionations associated with both physical and biochemical processes during cellulose synthesis in higher plants (Epstein & Krishnaumurthy, 1990; Roden et al., 2000; Saurer et al., 1997a; 1997b; 2000) can be used as archives for past climatic indicators. Superimposed on the climatic induced isotopic signal are the long-term responses of plant physiological processes to past changes in environmental conditions including CO2 enrichment.     

Lack of an Additive Effect between the Deletions of Klf5 and Nkx3-1 in Mouse Prostatic Tumorigenesis

Prostate cancer is one of the most common malignancies.The development and progression of prostate cancer are driven by a series of genetic and epigenetic events including gene amplification that activates oncogenes and chromosomal deletion that inactivates tumor suppressor genes.Whereas gene amplification occurs in human prostate cancer,gene deletion is more common,and a large number of chromosomal regions have been identified to have frequent deletion in prostate cancer,suggesting that tumor suppressor inactivation is more common than oncogene activation in prostatic carcinogenesis (Knuutila et al.,1998,1999;Dong,2001).Among the most frequently deleted chromosomal regions in prostate cancer,target genes such as NKX3-1 from 8p21,PTENfrom 10q23 andATBF1 from 16q22 have been identified by different approaches (He et al.,1997;Li et al.,1997;Sun et al.,2005),and deletion of these genes in mouse prostates has been demonstrated to induce and/or promote prostatic carcinogenesis.For example,knockout of Nkx3-1 in mice induces hyperplasia and dysplasia (Bhatia-Gaur et al.,1999;Abdulkadir et al.,2002) and promotes prostatic tumorigenesis (Abate-Shen et al.,2003),while knockout of Pten alone causes prostatic neoplasia (Wang et al.,2003).Therefore,gene deletion plays a causal role in prostatic carcinogenesis (Dong,2001).     

Genome-Wide Analysis and Expression Patterns of the YUCCA Genes in Maize

<正>Auxin plays important roles in various aspects of plant growth and development(Zhao,2010).In Arabidopsis,a number of YUCCA(YUC)genes,which are involved in auxin biosynthesis,have been identified(Zhao et al.,2001;Woodward et al.,2005;Cheng et al.,2006,2007;Kim et al.,2007;Chen et al.,2014).YUC genes encode flavin monooxygenases(FMOs)that convert indole-3-pyruvate(IPA)to indole-3-acetic acid(IAA)(Zhao,2012).The Arabidopsis YUC family is comprised of 11 members(Zhao et al.,2001;     

Genomic characterizations of H4 subtype avian influenza viruses from live poultry markets in Sichuan province of China, 2014–2015

正Dear Editor,Avian influenza viruses (AIVs) have posed a serious threat to poultry production and public health. To date, more than fourteen AIV subtypes that are able to infect human beings have been documented. Also, it is suggested that new subtypes may be reported in the future, owing to the migration of wild birds and live poultry transportation (Gao, 2018).Poultry may act as a potential incubator for novel subtypes of avian influenza virus (Bi et al., 2016a; Bi et al., 2016b; Liu et al., 2014a; Su et al., 2017). Up to date, the H7N9 AIV emerged in February 2013 has caused 1,567 human cases,with a fatality rate of 39.2%(http://www.who.int/influenza/     

Recent Advances in Cloning and Characterization of Disease Resistance Genes in Rice

Rice diseases caused by fungi, bacteria and viruses are one of the major constraints for sustainable rice （Oryza sativa L.） production worldwide. The use of resistant cultivars is considered the most economical and effective method to control rice diseases. In the last decade, a dozen resistance genes against the fungal pathogen Magnaporthe grisea and the bacterial pathogen Xanthomonas oryzae pv. oryzae have been cloned. Approximately half of them encode nuclear binding site （NBS） and leucine rich repeat （LRR）-containing proteins, the most common type of cloned plant resistance genes. Interestingly, four of them encode novel proteins which have not been identified in other plant species, suggesting that unique mechanisms might be involved in rice defense responses. This review summarizes the recent advances in cloning and characterization of disease resistance genes in rice and presents future perspectives for in-depth molecular analysis of the function and evolution of rice resistance genes and their interaction with avirulence genes in pathogens.     

SDG714 Regulates Specific Gene Expression and Consequently Affects Plant Growth via H3K9 Dimethylation

Histone lysine methylation is known to be involved in the epigenetic regulation of gene expression in all eukaryotes including plants. Here we show that the rice SDG714 is primarily responsible for dimethylation but not trimethylation on histone H3K9 in vivo. Overexpression of YFP-SDG714 in Arabidopsis significantly inhibits plant growth and this inhibition is associated with an enhanced level of H3K9 dimethylation. Our microarray results show that many genes essential for the plant growth and development were downregulated in transgenic Arabidopsis plants overexpressing YFP-SDG714. By chromatin immunoprecipitation analysis, we show that YFP-SDG714 is targeted to specific chromatin regions and dimethylate the H3K9, which is linked with heterochromatinization and the downregulation of genes. Most interestingly, when YFP-SDG714 production is stopped, the inhibited plants can partially restore their growth, suggesting that the perturbation of gene expression caused by YFP-SDG714 is revertible. Taken together, our results point to an important role of SDG714 in H3K9 dimethylation, suppression of gene expression and plant growth, and provide a potential method to regulate gene expression and plant development by an on-off switch of SDG714 expression.     

A Truncated F-Box Protein Confers the Dwarfism in Cucumber

正Dwarfism is an important plant architecture trait in crop breeding(Peng et al.,1999;Sasaki el al.,2002).In cucurbits.the compact plant type was proposed to develop new varieties for the once-over mechanical harvest for concentrated fruit set and higher densities(Li et al.,2011;Mondal et al.,2011).Several recessive genes in cucurbits have been reported to confer the phenotype of short internodes or bushy plant habits,such as compact,cp-2,and dw in cucumber(Cucumis sativus     

Anterograde and Retrograde Regulation of Nuclear Genes Encoding Mitochondrial Proteins during Growth,Development, and Stress

Mitochondrial biogenesis and function in plants require the expression of over 1000 nuclear genes encoding mitochondrial proteins （NGEMPs）. The expression of these genes is regulated by tissue-specific, developmental, internal, and external stimuli that result in a dynamic organelle involved in both metabolic and a variety of signaling processes. Although the metabolic and biosynthetic machinery of mitochondria is relatively well understood, the factors that regu- late these processes and the various signaling pathways involved are only beginning to be identified at a molecular level. The molecular components of anterograde （nuclear to mitochondrial） and retrograde （mitochondrial to nuclear） signaling pathways that regulate the expression of NGEMPs interact with chloroplast-, growth-, and stress-signaling pathways in the cell at a variety of levels, with common components involved in transmission and execution of these signals. This positions mitochondria as important hubs for signaling in the cell, not only in direct signaling of mitochondrial function per se, but also in sensing and/or integrating a variety of other internal and external signals. This integrates and optimizes growth with energy metabolism and stress responses, which is required in both photosynthetic and non-photosynthetic cells.