Latest Accepted Articles

Cell signaling leads the way
Author: Jia Li
Online Date: August 14, 2018
DOI: 10.1111/jipb.12707

Cells in plants, like in animals, constantly communicate with one another to coordinate their cellular activities in response to surrounding environmental conditions. Higher plants are multicellular organisms. A plant is originated from a single fertilized egg, which eventually develops into an intact individual with all necessary tissues and organs.

Abstract (Browse 12)   |   Full Text
  Letters to the Editor
Negative regulation of resistance protein©\mediated immunity by master transcription factors SARD1 and CBP60g
Author: Tongjun Sun, Wanwan Liang, Yuelin Zhang and Xin Li
Received: March 16, 2018         Accepted: July 10, 2018
Online Date: July 14, 2018
DOI: 10.1111/jipb.12698

Salicylic acid (SA) is an essential defence hormone in plants. Induced biosynthesis of SA, upon pathogen infection, is mediated by Isochorismate synthase 1 (ICS1), whose gene transcription is controlled mainly through two redundant transcription factors, SAR Deficient 1 (SARD1) and Calmodulin©\binding protein 60©\like g (CBP60g). Although these master transcription factors regulate not only positive, but also negative regulators of immunity, how they control signaling events downstream of different immune receptors is unclear. Using autoimmune mutants activating immunity mediated by different receptors, we show that, although the sard1 cbp60g double mutant almost fully suppresses the activation of defence mediated by suppressor of npr1©\1, constitutive 2 (snc2), it strikingly enhances snc1, which carries a gain©\of©\function mutation in an intracellular nucleotide©\binding leucine©\rich repeat (NLR) immune receptor. This negative regulation of immunity is achieved through the transcriptional regulation of negative regulators, such as NUCLEOSIDE DIPHOSPHATES LINKED TO SOME MOIETY X 6 (NUDT6). Our study highlights the diverse roles, especially the negative ones, in the regulation of plant immunity by the two master immune transcription factors SARD1 and CBP60g.

Abstract (Browse 32)   |   Full Text
Essential role of NbNOG1 in ribosomal RNA processing
Author: Jiangbo Guo, Shaojie Han, Jinping Zhao, Cuihua Xin, Xiyin Zheng, Yule Liu, Yan Wang and Feng Qu
Received: April 21, 2018         Accepted: June 21, 2018
Online Date: June 26, 2018
DOI: 10.1111/jipb.12691

Nucleolar GTP©\binding protein 1 (NOG1) is a highly conserved GTPase first reported in Trypanosoma as required for ribosome biogenesis. We characterized NbNOG1, a Nicotiana benthamiana NOG1 ortholog sharing more than 45% amino acid identity with Trypanosoma, yeast, and human NOG1. N. benthamiana plants silenced for NbNOG1 were stunted and produced sterile flowers. NbNOG1 is functionally interchangeable with yeast NOG1 (ScNOG1), rescuing yeast lethality caused by loss of ScNOG1. Finally, NbNOG1 silencing caused over©\accumulation of pre©\rRNA processing intermediates, and concomitant loss of mature rRNAs. Collectively, these data support a role for NbNOG1 in ribosomal RNA processing.

Abstract (Browse 55)   |   Full Text
  Special Issue: Cell Signaling
Cold signaling in plants: Insights into mechanisms and regulation
Author: Xiaoyu Guo, Dongfeng Liu and Kang Chong
Received: June 19, 2018         Accepted: August 8, 2018
Online Date: August 10, 2018
DOI: 10.1111/jipb.12706

To survive under cold temperatures plants must be able to perceive a cold signal and transduce it into downstream components that induce appropriate defense mechanisms. In addition to inducing adaptive defenses, such as the production of osmotic factors to prevent freezing and the reprogramming of transcriptional pathways, cold temperatures induce changes in plant growth and development which can affect the plant life cycle. In this review, we summarize recent progress in characterizing cold©\related genes and the pathways that allow transduction of the cold signal in plants, focusing primarily on studies in Arabidopsis thaliana and rice (Oryza sativa). We summarize cold perception and signal transduction from the plasma membrane to the nucleus, which involves cold sensors, calcium signals, calcium©\binding proteins, mitogen©\activated protein kinase cascades, and the C©\repeat binding factor (CBF)/dehydration©\responsive element binding (DREB) pathways, as well as trehalose metabolism. Finally, we describe the balance between plant organogenesis and cold tolerance mechanisms in rice. This review encapsulates the known cold signaling factors in plants and provides perspectives for ongoing cold signaling research.

Abstract (Browse 9)   |   Full Text
Molecular mechanisms governing plant responses to high temperatures
Author: Bingjie Li, Kang Gao, Huimin Ren and Wenqiang Tang
Received: June 30, 2018         Accepted: July 20, 2018
Online Date: July 20, 2018
DOI: 10.1111/jipb.12701

The increased prevalence of high temperatures (HTs) around the world is a major global concern, as they dramatically affect agronomic productivity. Upon HT exposure, plants sense the temperature change and initiate cellular and metabolic responses that enable them to adapt to their new environmental conditions. Decoding the mechanisms by which plants cope with HT is facilitating development of molecular markers to enable the production of plants with improved thermotolerance. In recent decades, genetic, physiological, molecular, and biochemical studies have revealed a number of vital cellular components and processes involved in thermoresponsive growth and the acquisition of thermotolerance in plants. This review summarizes the major mechanisms involved in plant HT responses, with a special focus on recent discoveries related to plant thermosensing, heat stress signaling, and HT©\regulated gene expression networks that promote plant adaptation to elevated environmental temperatures.

Abstract (Browse 17)   |   Full Text
The crossroads of receptor©\mediated signaling and endocytosis in plants
Author: Lucas Alves Neubus Claus, Daniel V. Savatin and Eugenia Russinova
Received: February 27, 2018         Accepted: June 5, 2018
Online Date: June 7, 2018
DOI: 10.1111/jipb.12672

Plants deploy numerous plasma membrane receptors to sense and rapidly react to environmental changes. Correct localization and adequate protein levels of the cell©\surface receptors are critical for signaling activation and modulation of plant development and defense against pathogens. After ligand binding, receptors are internalized for degradation and signaling attenuation. However, one emerging notion is that the ligand©\induced endocytosis of receptor complexes is important for the signaling duration, amplitude, and specificity. Recently, mutants of major endocytosis players, including clathrin and dynamin, have been shown to display defects in activation of a subset of signal transduction pathways, implying that signaling in plants might not be restricted to the plasma membrane only. Here, we summarize the up©\to©\date knowledge of receptor complex endocytosis and its effect on the signaling outcome in the context of plant development and immunity.

Abstract (Browse 63)   |   Full Text
Receptor©\like protein kinases: Key regulators controlling root hair development in Arabidopsis thaliana
Author: Zhuoyun Wei and Jia Li
Received: March 14, 2018         Accepted: April 27, 2018
Online Date: May 4, 2018
DOI: 10.1111/jipb.12663

Root hairs are tubular outgrowths specifically differentiated from epidermal cells in differentiation zone. The formation of root hairs greatly increases the surface area of a root and maximizes its ability to absorb water and inorganic nutrients essential for plant growth and development. Root hair development is strictly regulated by intracellular and intercellular signal communications. Cell surface©\localized receptor©\like protein kinases (RLKs) have been discovered as important components in these cellular processes. In this review, the functions of a number of key RLKs in regulating Arabidopsis root hair development are discussed, especially those involved in root epidermal cell fate determination and root hair tip growth.

Abstract (Browse 79)   |   Full Text
  Special Issue on Plant Synthetic Biology
Biotechnological approaches in glucosinolate production
Author: Annette Petersen, Cuiwei Wang, Christoph Crocoll and Barbara Ann Halkier
Received: May 5, 2018         Accepted: July 31, 2018
Online Date: August 6, 2018
DOI: 10.1111/jipb.12705

Glucosinolates (GLSs) are sulfur©\rich, amino acid©\derived defense compounds characteristic of the Brassicales order. In the past, GLSs were mostly known as anti©\nutritional factors in fodder, biopesticides in agriculture, and flavors in condiments such as mustard. However, in recent times, GLSs have received increased attention as promoters of human health. This has spurred intensive research towards generating rich sources of health©\promoting GLSs. We provide a comprehensive overview of the biotechnological approaches applied to reach this goal. This includes optimization of GLS production and composition in native, GLS©\producing plants, including hairy root and cell cultures thereof, as well as synthetic biology approaches in heterologous hosts, such as tobacco and the microbial organisms Escherichia coli and Saccharomyces cerevisiae. The progress using these different approaches is discussed.

Abstract (Browse 9)   |   Full Text
On the role of the tricarboxylic acid cycle in plant productivity
Author: Youjun Zhang and Alisdair R. Fernie
Received: June 4, 2018         Accepted: June 18, 2018
Online Date: June 19, 2018
DOI: 10.1111/jipb.12690

The tricarboxylic acid (TCA) cycle is one of the canonical energy pathways of living systems, as well as being an example of a pathway in which dynamic enzyme assemblies, or metabolons, are well characterized. The role of the enzymes have been the subject of saturated transgenesis approaches, whereby the expression of the constituent enzymes were reduced or knocked out in order to ascertain their in vivo function. Some of the resultant plants exhibited improved photosynthesis and plant growth, under controlled greenhouse conditions. In addition,overexpression of the endogenous genes, or heterologous forms of a number of the enzymes, has been carried out in tomato fruit and the roots of a range of species, and in some instances improvement in fruit yield and postharvest properties and plant performance, under nutrient limitation have been reported, respectively. Given a number of variants, in nature, we discuss possible synthetic approaches involving introducing these variants, or at least a subset of them, into plants. We additionally discuss the likely consequences of introducing synthetic metabolons, wherein certain pairs of reactions are artificially permanently assembled, into plants, and speculate as to future strategies to further improve plant productivity by manipulation of the core metabolic pathway.

Abstract (Browse 47)   |   Full Text
  Molecular Physiology
Trehalose phosphate synthase 5©\dependent trehalose metabolism modulates basal defense responses in Arabidopsis thaliana
Author: Xuelan Wang,Yan Du and Diqiu Yu
Received: March 15, 2018         Accepted: July 21, 2018
Online Date: July 30, 2018
DOI: 10.1111/jipb.12704

Despite the recent discovery that trehalose synthesis is important for plant development and abiotic stress tolerance, the effects of trehalose on biotic stress responses remain relatively unknown. In this study, we demonstrate that TREHALOSE PHOSPHATE SYNTHASE 5 (TPS5)©\dependent trehalose metabolism regulates Arabidopsis thaliana defenses against pathogens (necrotrophic Botrytis cinerea and biotrophic Pseudomonas syringae). Pathogen infection increased trehalose levels and up©\regulated TPS5 expression. The application of exogenous trehalose significantly improved plant defenses against B. cinerea, but increased the susceptibility of plants to P. syringae. We demonstrated that elevated trehalose biosynthesis, in transgenic plants over©\expressing TPS5, also increased the susceptibility to P. syringae, but decreased the disease symptoms caused by B. cinerea. The knockout of TPS5 prevented the accumulation of trehalose and enhanced defense responses against P. syringae. Additionally, we observed that a TPS5©\interacting protein (multiprotein bridging factor 1c) was required for induced expression of TPS5 during pathogen infections. Furthermore, we show that trehalose promotes P. syringae growth and disease development, via a mechanism involving suppression of the plant defense gene, Pathogenesis©\Related Protein 1. These findings provide insight into the function of TPS5©\dependent trehalose metabolism in plant basal defense responses.

Abstract (Browse 16)   |   Full Text
The central circadian clock proteins CCA1 and LHY regulate iron homeostasis in Arabidopsis
Author: Gang Xu, Zhimin Jiang, Haiyang Wang and Rongcheng Lin
Received: May 4, 2018         Accepted: July 6, 2018
Online Date: July 10, 2018
DOI: 10.1111/jipb.12696

Circadian clock is the endogenous time©\keeping machinery that synchronizes an organism's metabolism, behavior, and physiology to the daily light©\dark cicles, thereby contributing to organismal fitness. Iron (Fe) is an essential micronutrient for all organisms and it plays important roles in diverse processes of plant growth and development. Here, we show that, in Arabidopsis thaliana, loss of the central clock genes, CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY), results in both reduced Fe uptake and photosynthetic efficiency, whereas CCA1 overexpression confers the opposite effects. We show that root Fe(III) reduction activity, and expression of FERRIC REDUCTION OXIDASE 2 (FRO2) and IRON©\REGULATED TRANSPORTER 1 (IRT1) exhibit circadian oscillations, which are disrupted in the cca1 lhy double mutant. Furthermore, CCA1 directly binds to the specific regulatory regions of multiple Fe homeostasis genes and activates their expression. Thus, this study established that, in plants, CCA1 and LHY function as master regulators that maintain cyclic Fe homeostasis.

Abstract (Browse 37)   |   Full Text
Alleviation by ABA of Al toxicity in rice bean is not associated with citrate efflux but depends on ABI5©\mediated signal transduction pathways
Author: Wei Fan, Jia Meng Xu, Pei Wu, Zhi Xin Yang, He Qiang Lou, Wei Wei Chen, Jian Fen Jin, Shao Jian Zheng and Jian Li Yang
Received: April 14, 2018         Accepted: July 4, 2018
Online Date: July 5, 2018
DOI: 10.1111/jipb.12695

Under conditions of aluminum (Al) toxicity, which severely inhibits root growth in acidic soils, plants rapidly alter their gene expression to optimize physiological fitness for survival. Abscisic acid (ABA) has been suggested as a mediator between Al stress and gene expression, but the underlying mechanisms remain largely unknown. Here, we investigated ABA©\mediated Al©\stress responses, using integrated physiological and molecular biology approaches. We demonstrate that Al stress caused ABA accumulation in the root apex of rice bean (Vigna umbellata), which positively regulated Al tolerance. However, this was not associated with known Al©\tolerance mechanisms. Transcriptomic analysis revealed that nearly one©\third of the responsive genes were shared between the Al©\stress and ABA treatments. We further identified a transcription factor, ABI5, as being positively involved in Al tolerance. Arabidopsis abi5 mutants displayed increased sensitivity to Al, which was not related to the regulation of AtALMT1 and AtMATE expression. Functional categorization of ABI5©\mediated genes revealed the importance of cell wall modification and osmoregulation in Al tolerance, a finding supported by osmotic stress treatment on Al tolerance. Our results suggest that ABA signal transduction pathways provide an additional layer of regulatory control over Al tolerance in plants.

Abstract (Browse 29)   |   Full Text
  Functional Omics and Systems Biology
Genome©\wide screening of long non©\coding RNAs involved in rubber biosynthesis in Eucommia ulmoides
Author: Huimin Liu, Yan Lu, Juan Wang, Jingjing Hu, Tana Wuyun
Received: March 2, 2018         Accepted: June 25, 2018
Online Date: June 26, 2018
DOI: 10.1111/jipb.12693

Increasing evidence indicates that long non©\coding RNAs (lncRNAs) play pivotal roles in regulatory networks controlling plant and animal gene expression. However, the roles of lncRNAs in regulating rubber biosynthesis in Eucommia ulmoides, an emerging source of natural rubber (Eu©\rubber), are currently unknown. Here, we performed deep RNA sequencing of two parts of E. ulmoides fruits at two developmental time points. Using a stringent pipeline, we identified 29,103 lncRNAs and 9,048 transcripts of uncertain coding potential (TUCPs). Two differentially expressed (DE) TUCPs appear to simultaneously regulate 12 protein©\coding genes involved in Eu©\rubber biosynthesis (GIEBs), as well as 95 DE genes. Functional categorization of these 95 DE genes revealed that they are mainly related to subcellular microstructures and cellular processes, such as cell wall, cell division, and growth. These DE genes might be involved in the differentiation and development of laticifers, where Eu©\rubber is synthesized. The “commanders” (DE TUCPs) likely cause the “builders” (DE genes) to construct the “storehouse” of materials needed for Eu©\rubber synthesis and the “workers” (GIEBs) to synthesize Eu©\rubber. These findings provide insights into both cis©\ and trans©\polyisoprene biosynthesis in plants, laying the foundation for additional studies of this crucial process.

Abstract (Browse 39)   |   Full Text
  Cell and Developmental Biology
A C3HC4©\type RING finger protein regulates rhizobial infection and nodule organogenesis in Lotus japonicus
Author: Kai Cai, Jun Yin, Hongmin Chao, Yaping Ren, Liping Jin, Yangrong Cao, Deqiang Duanmu and Zhongming Zhang
Received: April 9, 2018         Accepted: July 22, 2018
Online Date: July 26, 2018
DOI: 10.1111/jipb.12703

During the establishment of rhizobia©\legume symbiosis, the cytokinin receptor LHK1 (Lotus Histidine Kinase 1) is essential for nodule formation. However, the mechanism by which cytokinin signaling regulates symbiosis remains largely unknown. In this study, an LHK1©\interacting protein, LjCZF1, was identified and further characterized. LjCZF1 is a C3HC4©\type RING finger protein that is highly conserved in plants. LjCZF1 specifically interacted with LHK1 in yeast two©\hybrid, in vitro pull©\down and co©\immunoprecipitation assays conducted in tobacco. Phosphomimetic mutation of the potential threonine (T167D) phosphorylation site enhanced the interaction between LjCZF1 and LHK1, whereas phosphorylation mutation (T167A) eliminated this interaction. Transcript abundance of LjCZF1 was up©\regulated significantly after inoculation with rhizobia. The LORE1 insertion mutant and CRISPR/Cas9©\mediated knockout mutant Lotus japonicus plants demonstrated significantly reduced number of infection threads and nodules. In contrast, plants over©\expressing LjCZF1 exhibited increased numbers of infection threads and nodules. Collectively, these data support the notion that LjCZF1 is a positive regulator of symbiotic nodulation, possibly through interaction with LHK1.

Abstract (Browse 17)   |   Full Text
Rab©\H1b Is Essential for Trafficking of Cellulose Synthase and for Hypocotyl Growth in Arabidopsis thaliana
Author: Ming He, Miao Lan, Baocai Zhang, Yihua Zhou, Youqun Wang, Lei Zhu, Ming Yuan, and Ying Fu
Received: April 22, 2018         Accepted: July 3, 2018
Online Date: July 5, 2018
DOI: 10.1111/jipb.12694

Cell©\wall deposition of cellulose microfibrils is essential for plant growth and development. In plant cells, cellulose synthesis is accomplished by cellulose synthase complexes located in the plasma membrane. Trafficking of the complex between endomembrane compartments and the plasma membrane is vital for cellulose biosynthesis; however, the mechanism for this process is not well understood. We here report that, in Arabidopsis thaliana, Rab©\H1b, a Golgi©\localized small GTPase, participates in the trafficking of CELLULOSE SYNTHASE 6 (CESA6) to the plasma membrane. Loss of Rab©\H1b function resulted in altered distribution and motility of CESA6 in the plasma membrane and reduced cellulose content. Seedlings with this defect exhibited short, fragile etiolated hypocotyls. Exocytosis of CESA6 was impaired in rab©\h1b cells, and endocytosis in mutant cells was significantly reduced as well. We further observed accumulation of vesicles around an abnormal Golgi apparatus having an increased number of cisternae in rab©\h1b cells, suggesting a defect in cisternal homeostasis caused by Rab©\H1b loss function. Our findings link Rab GTPases to cellulose biosynthesis, during hypocotyl growth, and suggest Rab©\H1b is crucial for modulating the trafficking of cellulose synthase complexes between endomembrane compartments and the plasma membrane and for maintaining Golgi organization and morphology.

Abstract (Browse 41)   |   Full Text
OsPKp¦Á1 encodes a plastidic pyruvate kinase that affects starch biosynthesis in the rice endosperm
Author: Yue Cai, Wenwei Zhang, Jie Jin, Xiaoming Yang, Xiaoman You, Haigang Yan, Liang Wang, Jie Chen, Jiahuan Xu, Weiwei Chen, Xingang Chen, Jing Ma, Xiaojie Tang, Fei Kong, Xiaopin Zhu, Guoxiang Wang, Ling Jiang, William Terzaghi, Chunming Wang and Jianmin Wan
Received: March 14, 2018         Accepted: June 25, 2018
Online Date: June 26, 2018
DOI: 10.1111/jipb.12692

Pyruvate kinase (PK) is a key enzyme in glycolysis and carbon metabolism. Here, we isolated a rice (Oryza sativa) mutant, w59, with a white©\core floury endosperm. Map©\based cloning of w59 identified a mutation in OsPKpα1, which encodes a plastidic isoform of PK (PKp). OsPKpα1 localizes to the amyloplast stroma in the developing endosperm, and the mutation of OsPKpα1 in w59 decreases the plastidic PK activity, resulting in dramatic changes to the lipid biosynthesis in seeds. The w59 grains were also characterized by a marked decrease in starch content. Consistent with a decrease in number and size of the w59 amyloplasts, large empty spaces were observed in the central region of the w59 endosperm, at the early grain©\filling stage. Moreover, a phylogenetic analysis revealed four potential rice isoforms of OsPKp. We validated the in vitro PK activity of these OsPKps through reconstituting active PKp complexes derived from inactive individual OsPKps, revealing the heteromeric structure of rice PKps, which was further confirmed using a protein©\protein interaction analysis. These findings suggest a functional connection between lipid and starch synthesis in rice endosperm amyloplasts.

Abstract (Browse 42)   |   Full Text
  Molecular Ecology and Evolution
Environmental drivers and genomic architecture of trait differentiation in fire©\adapted Banksia attenuata ecotypes
Author: Tianhua He, Byron B. Lamont, Neal J. Enright, Haylee M. D¡¯Agui, William Stock
Received: February 9, 2018         Accepted: July 10, 2018
Online Date: July 11, 2018
DOI: 10.1111/jipb.12697

Trait divergence between populations is considered an adaptive response to different environments, but to what extent this response is accompanied by genetic differentiation is less clear since it may be phenotypic plasticity. In this study, we analysed phenotypic variation between two Banksia attenuata growth forms, lignotuberous (shrub) and epicormic resprouting (tree), in fire©\prone environments to identify the environmental factors that have driven this phenotypic divergence. We linked genotype with phenotype and traced candidate genes using differential gene expression analysis. Fire intervals determined the phenotypic divergence between growth forms in B. attenuata. Genome©\wide association study identified 69 single nucleotide polymorphisms, putatively associated with growth form, whereas no growth form©\ or phenotype©\specific genotypes were identified. Genomic differentiation between the two growth forms was low (Fst = 0.024). Differential gene expression analysis identified 37 genes/transcripts that were differentially expressed in the two growth forms. A small heat©\shock protein gene, associated with lignotuber presence, was differentially expressed in the two forms. We conclude that different fire regimes induce phenotypic polymorphism in B. attenuata, whereas phenotypic trait divergence involves the differential expression of a small fraction of genes that interact strongly with the disturbance regime. Thus, phenotypic plasticity among resprouters is the general strategy for surviving varying fire regimes.

Abstract (Browse 36)   |   Full Text
Tecia solanivora infestation increases tuber starch accumulation inPastusa Suprema potatoes
Author: Pavan Kumar, Etzel Garrido, Kun Zhao, Yi Zheng, Saleh Alseekh, Erandi Vargas-Ortiz, Alisdair R. Fernie, Zhangjun Fei, Katja Poveda and Georg Jander
Received: May 4, 2018         Accepted: June 7, 2018
Online Date: June 11, 2018
DOI: 10.1111/jipb.12675

In response to infestation with larvae of the Guatemalan tuber moth (Tecia solanivora), some Solanum tuberosum (potato) varieties exhibit an overcompensation response, whereby the total dry mass of uninfested tubers is increased. Here, we describe early responses, within the first few days, of T. solanivora feeding, in the Colombian potato variety Pastusa Suprema. Non©\targeted metabolite profiling showed significant secondary metabolism changes in T. solanivora©\infested tubers, but not in uninfested systemic tubers. In contrast, changes in primary metabolism were greater in uninfested systemic tubers than in the infested tubers, with a notable 80% decline in systemic tuber sucrose levels within one day of T. solanivora infestation. This suggested either decreased sucrose transport from the leaves or increased sink strength, i.e. more rapid sucrose to starch conversion in the tubers. Increased, sucrose synthesis was indicated by higher rubicso activase and lower starch synthase gene expression in the leaves of infested plants. Elevated sink strength was demonstrated by 45% more total starch deposition in systemic tubers of T. solanivora©\infested plants compared to uninfested control plants. Thus, rather than investing in increased defense of uninfested tubers, Pastusa Suprema promotes deposition of photoassimilates in the form of starch as a response to T. solanivora infestation.

Abstract (Browse 49)   |   Full Text
Maintenance of species boundaries in three sympatric Ligularia (Senecioneae, Asteraceae) species
Author: Ningning Zhang, Yongpeng Ma, Ryan A. Folk, Jiaojun Yu, Yuezhi Pan and Xun Gong
Received: April 10, 2018         Accepted: May 31, 2018
Online Date: June 7, 2018
DOI: 10.1111/jipb.12674

The key process in speciation concerns the formation and maintenance of reproductive isolating barriers between diverging lineages. Although species boundaries are frequently investigated between two species across many taxa, reproductive isolating barriers among multiple species (>2) that would represent the most common phenomenon in the nature, remain to be clarified. Here, we use double digest restriction©\site associated DNA (ddRAD) sequencing to examine patterns of hybridization at a sympatric site where three Ligularia species grow together and verify whether those patterns contribute to the maintenance of boundaries among species. The results based on the RAD SNP datasets indicated hybridization L. cyathiceps × L. duciformis and L. duciformis × L. yunnanensis were both restricted to F1s plus a few first©\generation backcrosses and no gene introgression were identified, giving rise to strong reproductive isolation among hybridizing species. Moreover, hybrid swarm simulation, using HYBRIDLAB, indicated the RAD SNP datasets had sufficient discriminatory power for accurate hybrid detection. We conclude that parental species show strong reproductive isolation and they still maintain species boundaries, which may be the key mechanism to maintain species diversity of Ligualria in the eastern Qinghai©\Tibetan Plateau and adjacent areas. Moreover, this study highlights the effectiveness of RAD sequencing in hybridization studies.

Abstract (Browse 60)   |   Full Text
  Metabolism and Biochemistry
Efficient iron plaque formation on tea (Camellia sinensis) roots contributes to acidic stress tolerance
Author: Xianchen Zhang, Honghong Wu, Lingmu Chen, Yeyun Li, Xiaochun Wan
Received: April 26, 2018         Accepted: July 19, 2018
Online Date: July 23, 2018
DOI: 10.1111/jipb.12702

Tea plants grow in acidic soil, but to date, their intrinsic mechanisms of acidic stress tolerance have not been elucidated. Here, we assessed the tea plant response to growth on NH4+ nutrient media having different pH and iron levels. When grown in standard NH4+ nutrient solution (iron insufficient, 0.35 mg L−1 Fe2+), tea roots exhibited significantly lower nitrogen accumulation, plasma membrane H+©\ATPase activity, and protein levels; net H+ efflux was lower at pH 4.0 and 5.0 than at pH 6.0. Addition of 30 mg L−1 Fe2+ (iron sufficient, mimicking normal soil Fe2+ concentrations) to the NH4+ nutrient solution led to more efficient iron plaque formation on roots and increased root plasma membrane H+©\ATPase levels and activities at pH 4.0 and 5.0, compared to the pH 6.0 condition. Furthermore, plants grown at pH 4.0 and 5.0, with sufficient iron, exhibited significantly higher nitrogen accumulation than those grown at pH 6.0. Together, these results support the hypothesis that efficient iron plaque formation, on tea roots, is important for acidic stress tolerance. Furthermore, our findings establish that efficient iron plaque formation is linked to increased levels and activities of the tea root plasma membrane H+©\ATPase, under low pH conditions.

Abstract (Browse 18)   |   Full Text
Crystal structure of Arabidopsis thaliana RabA1a
Author: Ji-Sook Yun, Sung Chul Ha, Shinae Kim, Yeon-Gil Kim, Hyeran Kim, and Jeong Ho Chang
Received: May 15, 2018         Accepted: July 11, 2018
Online Date: July 16, 2018
DOI: 10.1111/jipb.12700

RabGTPase is a member of the Ras superfamily of small GTPases, which share a GTP©\binding pocket containing highly conserved motifs that promote GTP hydrolysis. In Arabidopsis, the RabA group, which corresponds to the Rab11 group in animals, functions in the recycling of endosomes that control docking and fusion during vesicle transport. However, their molecular mechanisms remain unknown. In this study, we determined the crystal structures of the GDP©\bound inactive form and both GppNHp©\ and GTP©\bound active forms of RabA1a, at resolutions of 2.8, 2.6, and 2.6 Å, respectively. A bound sulfate ion in the active site of the GDP©\bound structure stabilized Switch II by bridging the interaction between a magnesium ion and Arg74. Comparisons of the two states of RabA1a with Rab11 proteins revealed clear differences in the Switch I and II loops. These results suggested that conformational change of the Switch regions of RabA1a, derived by GTP or GDP binding, could maintain subcellular membrane traffic through the specific interaction of effector molecules.

Abstract (Browse 20)   |   Full Text

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