Early View

  Special Issue: Cell Signaling
Unraveling salt stress signaling in plants
Author: Yongqing Yang and Yan Guo
Received: January 30, 2018         Accepted: June 8, 2018
Online Date: June 15, 2018
DOI: 10.1111/jipb.12689

Salt stress is a major environmental factor limiting plant growth and productivity. A better understanding of the mechanisms mediating salt resistance will help researchers design ways to improve crop performance under adverse environmental conditions. Salt stress can lead to ionic stress, osmotic stress and secondary stresses, particularly oxidative stress, in plants. Therefore, to adapt to salt stress, plants rely on signals and pathways that re©\establish cellular ionic, osmotic, and reactive oxygen species (ROS) homeostasis. Over the past two decades, genetic and biochemical analyses have revealed several core stress signaling pathways that participate in salt resistance. The Salt Overly Sensitive signaling pathway plays a key role in maintaining ionic homeostasis, via extruding sodium ions into the apoplast. Mitogen©\activated protein kinase cascades mediate ionic, osmotic, and ROS homeostasis. SnRK2 (sucrose nonfermenting 1©\related protein kinase 2) proteins are involved in maintaining osmotic homeostasis. In this review, we discuss recent progress in identifying the components and pathways involved in the plant's response to salt stress and their regulatory mechanisms. We also review progress in identifying sensors involved in salt©\induced stress signaling in plants.

Abstract (Browse 64)   |   References   |   Full Text HTML   |   Full Text PDF       
Ethylene©\induced microtubule reorientation is essential for fast inhibition of root elongation in Arabidopsis
Author: Yichuan Wang, Yusi Ji, Ying Fu and Hongwei Guo
Received: February 8, 2018         Accepted: May 9, 2018
Online Date: May 12, 2018
DOI: 10.1111/jipb.12666

Microtubule reorientation is a long©\standing observation that has been implicated in regulating the inhibitory effect of ethylene on axial elongation of plant cells. However, the signaling mechanism underlying ethylene©\induced microtubule reorientation has remained elusive. Here, we reveal, by live confocal imaging and kinetic root elongation assays, that the time courses of ethylene©\induced microtubule reorientation and root elongation inhibition are highly correlated, and that microtubule reorientation is required for the full responsiveness of root elongation to ethylene treatment. Our genetic analysis demonstrated that the effect of ethylene on microtubule orientation and root elongation is mainly transduced through the canonical linear ethylene signaling pathway. By employing pharmacological and genetic analyses, we demonstrate further that the TIR1/AFBs©\Aux/IAAs©\ARFs auxin signaling pathway, but not the ABP1©\ROP6©\RIC1 auxin signaling branch, is essential for ethylene©\induced microtubule reorientation and root elongation inhibition. Together, these findings offer evidence for the functional significance and elucidate the signaling mechanism for ethylene©\induced microtubule reorientation in fast root elongation inhibition in Arabidopsis.

Abstract (Browse 98)   |   References   |   Full Text HTML   |   Full Text PDF       
Insights into the regulation of C©\repeat binding factors in plant cold signaling
Author: Jingyan Liu, Yiting Shi, and Shuhua Yang
Received: February 18, 2018         Accepted: April 16, 2018
Online Date: April 18, 2018
DOI: 10.1111/jipb.12657

Cold temperatures, a major abiotic stress, threaten the growth and development of plants, worldwide. To cope with this adverse environmental cue, plants from temperate climates have evolved an array of sophisticated mechanisms to acclimate to cold periods, increasing their ability to tolerate freezing stress. Over the last decade, significant progress has been made in determining the molecular mechanisms underpinning cold acclimation, including following the identification of several pivotal components, including candidates for cold sensors, protein kinases, and transcription factors. With these developments, we have a better understanding of the CBF©\dependent cold©\signaling pathway. In this review, we summarize recent progress made in elucidating the cold©\signaling pathways, especially the C©\repeat binding factor©\dependent pathway, and describe the regulatory function of the crucial components of plant cold signaling. We also discuss the unsolved questions that should be the focus of future work.

Abstract (Browse 93)   |   References   |   Full Text HTML   |   Full Text PDF       
Phosphatidic acid plays key roles regulating plant development and stress responses
Author: Hong-Yan Yao and Hong-Wei Xue
Received: February 27, 2018         Accepted: April 11, 2018
Online Date: April 16, 2018
DOI: 10.1111/jipb.12655

Phospholipids, including phosphatidic acid (PA), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), phosphatidylserine (PS) and phosphoinositides, have emerged as an important class of cellular messenger molecules in various cellular and physiological processes, of which PA attracts much attention of researchers. In addition to its effect on stimulating vesicle trafficking, many studies have demonstrated that PA plays a crucial role in various signaling pathways by binding target proteins and regulating their activity and subcellular localization. Here, we summarize the functional mechanisms and target proteins underlying PA©\mediated regulation of cellular signaling, development, hormonal responses, and stress responses in plants.

Abstract (Browse 119)   |   References   |   Full Text HTML   |   Full Text PDF       
Reactive oxygen species signaling and stomatal movement in plant responses to drought stress and pathogen attack
Author: Junsheng Qi, Chun-Peng Song, Baoshan Wang, Jianmin Zhou, Jaakko Kangasjärvi, Jian-Kang Zhu and Zhizhong Gong
Received: February 20, 2018         Accepted: April 8, 2018
Online Date: April 16, 2018
DOI: 10.1111/jipb.12654

Stomata, the pores formed by a pair of guard cells, are the main gateways for water transpiration and photosynthetic CO2 exchange, as well as pathogen invasion in land plants. Guard cell movement is regulated by a combination of environmental factors, including water status, light, CO2 levels and pathogen attack, as well as endogenous signals, such as abscisic acid and apoplastic reactive oxygen species (ROS). Under abiotic and biotic stress conditions, extracellular ROS are mainly produced by plasma membrane©\localized NADPH oxidases, whereas intracellular ROS are produced in multiple organelles. These ROS form a sophisticated cellular signaling network, with the accumulation of apoplastic ROS an early hallmark of stomatal movement. Here, we review recent progress in understanding the molecular mechanisms of the ROS signaling network, primarily during drought stress and pathogen attack. We summarize the roles of apoplastic ROS in regulating stomatal movement, ABA and CO2 signaling, and immunity responses. Finally, we discuss ROS accumulation and communication between organelles and cells. This information provides a conceptual framework for understanding how ROS signaling is integrated with various signaling pathways during plant responses to abiotic and biotic stress stimuli.

Abstract (Browse 125)   |   References   |   Full Text HTML   |   Full Text PDF       
  New Technology
Calcium imaging in Arabidopsis pollen cells using G©\CaMP5
Author: Min Diao, Xiaolu Qu and Shanjin Huang
Received: January 17, 2018         Accepted: February 7, 2018
Online Date: February 9, 2018
DOI: 10.1111/jipb.12642

Calcium (Ca2+) signaling has been implicated in pollen germination and pollen tube growth. To date, however, we still know very little about how exactly Ca2+ signaling links to various physiological subcellular processes during pollen germination and pollen tube growth. Given that Ca2+ signaling is tightly related to the cytosolic concentration and dynamics of Ca2+, it is vital to trace the dynamic changes in Ca2+ levels in order to decode Ca2+ signaling. Here, we demonstrate that G©\CaMP5 serves well as an indicator for monitoring cytosolic Ca2+ dynamics in pollen cells. Using this probe, we show that cytosolic Ca2+ changes dramatically during pollen germination, and, as reported previously, Ca2+ forms a tip©\focused gradient in the pollen tube and undergoes oscillation in the tip region during pollen tube growth. In particular, using G©\CaMP5 allowed us to capture the dynamic changes in the cytosolic Ca2+ concentration ([Ca2+]cyt) in pollen tubes in response to various exogenous treatments. Our data suggest that G©\CaMP5 is a suitable probe for monitoring the dynamics of [Ca2+]cyt in pollen cells.

Abstract (Browse 252)   |   References   |   Full Text HTML   |   Full Text PDF       
  Cell and Developmental Biology
Proteome analysis of peroxisomes from dark©\treated senescent Arabidopsis leaves
Author: Ronghui Pan, Sigrun Reumann, Piotr Lisik, Stefanie Tietz, Laura J. Olsen and Jianping Hu
Received: May 8, 2018         Accepted: May 29, 2018
Online Date: June 7, 2018
DOI: 10.1111/jipb.12670

Peroxisomes compartmentalize a dynamic suite of biochemical reactions and play a central role in plant metabolism, such as the degradation of hydrogen peroxide, metabolism of fatty acids, photorespiration, and the biosynthesis of plant hormones. Plant peroxisomes have been traditionally classified into three major subtypes, and in©\depth mass spectrometry (MS)©\based proteomics has been performed to explore the proteome of the two major subtypes present in green leaves and etiolated seedlings. Here, we carried out a comprehensive proteome analysis of peroxisomes from Arabidopsis leaves given a 48©\h dark treatment. Our goal was to determine the proteome of the third major subtype of plant peroxisomes from senescent leaves, and further catalog the plant peroxisomal proteome. We identified a total of 111 peroxisomal proteins and verified the peroxisomal localization for six new proteins with potential roles in fatty acid metabolism and stress response by in vivo targeting analysis. Metabolic pathways compartmentalized in the three major subtypes of peroxisomes were also compared, which revealed a higher number of proteins involved in the detoxification of reactive oxygen species in peroxisomes from senescent leaves. Our study takes an important step towards mapping the full function of plant peroxisomes.

Abstract (Browse 64)   |   References   |   Full Text HTML   |   Full Text PDF       
Non©\dormant Axillary Bud 1 regulates axillary bud outgrowth in sorghum  
Author: Jun Chen, Limin Zhang, Mengjiao Zhu, Lijie Han, Ya Lv, Yishan Liu, Pan Li, Haichun Jing and Hongwei Cai
Received: April 3, 2018         Accepted: May 4, 2018
Online Date: May 9, 2018
DOI: 10.1111/jipb.12665

Tillering contributes to grain yield and plant architecture and therefore is an agronomically important trait in sorghum (Sorghum bicolor). Here, we identified and functionally characterized a mutant of the Non©\dormant Axillary Bud 1 (NAB1) gene from an ethyl methanesulfonate©\mutagenized sorghum population. The nab1 mutants have increased tillering and reduced plant height. Map©\based cloning revealed that NAB1 encodes a carotenoid©\cleavage dioxygenase 7 (CCD7) orthologous to rice (Oryza sativa) HIGH©\TILLERING DWARF1/DWARF17 and Arabidopsis thaliana MORE AXILLARY BRANCHING 3. NAB1 is primarily expressed in axillary nodes and tiller bases and NAB1 localizes to chloroplasts. The nab1 mutation causes outgrowth of basal axillary buds; removing these non©\dormant basal axillary buds restored the wild©\type phenotype. The tillering of nab1 plants was completely suppressed by exogenous application of the synthetic strigolactone analog GR24. Moreover, the nab1 plants had no detectable strigolactones and displayed stronger polar auxin transport than wild©\type plants. Finally, RNA©\seq showed that the expression of genes involved in multiple processes, including auxin©\related genes, was significantly altered in nab1. These results suggest that NAB1 functions in strigolactone biosynthesis and the regulation of shoot branching via an interaction with auxin transport.

Abstract (Browse 89)   |   References   |   Full Text HTML   |   Full Text PDF       
  Plant-abiotic Interactions
Arabidopsis small ubiquitin©\related modifier protease ASP1 positively regulates abscisic acid signaling during early seedling development  
Author: Qiongli Wang, Gao-Ping Qu, Xiangxiong Kong, Yan Yan, Jigang Li and Jing Bo Jin
Received: April 8, 2018         Accepted: May 10, 2018
Online Date: May 22, 2018
DOI: 10.1111/jipb.12669

The small ubiquitin©\related modifier (SUMO) modification plays an important role in the regulation of abscisic acid (ABA) signaling, but the function of the SUMO protease, in ABA signaling, remains largely unknown. Here, we show that the SUMO protease, ASP1 positively regulates ABA signaling. Mutations in ASP1 resulted in an ABA©\insensitive phenotype, during early seedling development. Wild©\type ASP1 successfully rescued, whereas an ASP1 mutant (C577S), defective in SUMO protease activity, failed to rescue, the ABA©\insensitive phenotype of asp1©\1. Expression of ABI5 and MYB30 target genes was attenuated in asp1©\1 and our genetic analyses revealed that ASP1 may function upstream of ABI5 and MYB30. Interestingly, ASP1 accumulated upon ABA treatment, and ABA©\induced accumulation of ABI5 (a positive regulator of ABA signaling) was abolished, whereas ABA©\induced accumulation of MYB30 (a negative regulator of ABA signaling) was increased in asp1©\1. These findings support the hypothesis that increased levels of ASP1, upon ABA treatment, tilt the balance between ABI5 and MYB30 towards ABI5©\mediated ABA signaling.

Abstract (Browse 83)   |   References   |   Full Text HTML   |   Full Text PDF       
  Invited Expert Review
Expanding roles for pectins in plant development
Author: Adam M. Saffer
Received: March 23, 2018         Accepted: May 2, 2018
Online Date: May 4, 2018
DOI: 10.1111/jipb.12662

Pectins are complex cell wall polysaccharides important for many aspects of plant development. Recent studies have discovered extensive physical interactions between pectins and other cell wall components, implicating pectins in new molecular functions. Pectins are often localized in spatially restricted patterns, and some of these non©\uniform pectin distributions contribute to multiple aspects of plant development, including the morphogenesis of cells and organs. Furthermore, a growing number of mutants affecting cell wall composition have begun to reveal the distinct contributions of different pectins to plant development. This review discusses the interactions of pectins with other cell wall components, the functions of pectins in controlling cellular morphology, and how non©\uniform pectin composition can be an important determinant of developmental processes.

Abstract (Browse 93)   |   References   |   Full Text HTML   |   Full Text PDF       
  Molecular Physiology
Identification of novel cis©\elements bound by BplMYB46 involved in abiotic stress responses and secondary wall deposition  
Author: Huiyan Guo, Liuqiang Wang, Chuanping Yang, Yiming Zhang, Chunrui Zhang, Chao Wang
Received: February 19, 2018         Accepted: June 1, 2018
Online Date: June 7, 2018
DOI: 10.1111/jipb.12671

Transcription factors (TFs) play vital roles in various biological processes by binding to cis©\acting elements to control expressions of their target genes. The MYB TF BplMYB46, from Betula platyphylla, is involved in abiotic stress responses and secondary wall deposition. In the present study, we used a TF©\centered yeast one©\hybrid technology (TF©\centered Y1H) to identify the cis©\acting elements bound by BplMYB46. We screened a short©\insert random library and identified three cis©\elements bound by BplMYB46: an E©\box (CA(A/T/C)(A/G/C)TG) and two novel motifs, a TC©\box (T(G/A)TCG(C/G)) and a GT©\box (A(G/T)T(A/C)GT(T/G)C). Chromatin immunoprecipitation (ChIP) and effector©\reporter coexpression assays in Nicotiana tabacum confirmed binding of BplMYB46 to the TC©\box, GT©\box, and E©\box motifs in the promoters of the phenylalanine ammonia lyase (PAL), peroxidase (POD), and superoxide dismutase (SOD) genes, which function in abiotic stress tolerance and secondary wall biosynthesis. This finding improves our understanding of potential regulatory mechanisms in the response to abiotic stress and secondary wall deposition of BplMYB46 in B. platyphylla.

Abstract (Browse 76)   |   References   |   Full Text HTML   |   Full Text PDF       
Arabidopsis VQ10 interacts with WRKY8 to modulate basal defense against Botrytis cinerea
Author: Junqiu Chen, Houping Wang, Yang Li, Jinjing Pan, Yanru Hu and Diqiu Yu
Received: March 15, 2018         Accepted: May 3, 2018
Online Date: May 4, 2018
DOI: 10.1111/jipb.12664

Recent studies in Arabidopsis have revealed that some VQ motif©\containing proteins physically interact with WRKY transcription factors; however, their specific biological functions are still poorly understood. In this study, we confirmed the interaction between VQ10 and WRKY8, and show that VQ10 and WRKY8 formed a complex in the plant cell nucleus. Yeast two©\hybrid analysis showed that the middle region of WRKY8 and the VQ motif of VQ10 are critical for their interaction, and that this interaction promotes the DNA©\binding activity of WRKY8. Further investigation revealed that the VQ10 protein was exclusively localized in the nucleus, and VQ10 was predominantly expressed in siliques. VQ10 expression was strongly responsive to the necrotrophic fungal pathogen, Botrytis cinerea and defense©\related hormones. Phenotypic analysis showed that disruption of VQ10 increased mutant plants susceptibility to the fungal pathogen B. cinerea, whereas constitutive©\expression of VQ10 enhanced resistance to B. cinerea. Consistent with these findings, expression of the defense©\related PLANT DEFENSIN1.2 (PDF1.2) gene was decreased in vq10 mutant plants, after B. cinerea infection, but increased in VQ10©\overexpressing transgenic plants. Taken together, our findings provide evidence that VQ10 physically interacts with WRKY8 and positively regulates plant basal resistance against the necrotrophic fungal pathogen B. cinerea.

Abstract (Browse 97)   |   References   |   Full Text HTML   |   Full Text PDF       
  Functional Omics and Systems Biology
A genome©\wide association study of early©\maturation traits in upland cotton based on the CottonSNP80K array  
Author: Chengqi Li, Yuanyuan Wang, Nijiang Ai, Yue Li and Jiafeng Song
Received: February 2, 2018         Accepted: May 31, 2018
Online Date: June 7, 2018
DOI: 10.1111/jipb.12673

Genome©\wide association studies (GWASs) efficiently identify genetic loci controlling traits at a relatively high resolution. In this study, variations in major early©\maturation traits, including seedling period (SP), bud period (BP), flower and boll period (FBP), and growth period (GP), of 169 upland cotton accessions were investigated, and a GWAS of early maturation was performed based on a CottonSNP80K array. A total of 49,650 high©\quality single©\nucleotide polymorphisms (SNPs) were screened, and 29 significant SNPs located on chromosomes A6, A7, A8, D1, D2, and D9, were repeatedly identified as associated with early©\maturation traits, in at least two environments or two algorithms. Of these 29 significant SNPs, 1, 12, 11, and 5 were related to SP, BP, FBP, and GP, respectively. Six peak SNPs, TM47967, TM13732, TM20937, TM28428, TM50283, and TM72552, exhibited phenotypic contributions of approximately 10%, which could allow them to be used for marker©\assisted selection. One of these, TM72552, as well as four other SNPs, TM72554, TM72555, TM72558, and TM72559, corresponded to the quantitative trait loci previously reported. In total, 274 candidate genes were identified from the genome sequences of upland cotton and were categorized based on their functional annotations. Finally, our studies identified Gh_D01G0340 and Gh_D01G0341 as potential candidate genes for improving cotton early maturity.

Abstract (Browse 76)   |   References   |   Full Text HTML   |   Full Text PDF       

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