February 2013, Volume 55 Issue 2, Pages 122ĘC198.

Cover Caption: Polarity Setup in Regenerating Protoplasts
About the cover: Regenerating tobacco BY-2 protoplasts are suitable for studying cell polarity and axis formation. In this issue, Zaban et al. (pp. 142ĘC159) present a model showing the microtubule cytoskeleton conveys positional information between the nucleus and membrane, to control the cell wall formation and the establishment of a new axis.


          New Technology
An Efficient Rice Mutagenesis System based on Suspension-Cultured Cells
Author: Yuan-Ling Chen, Hui-Lin Liang, Xing-Liang Ma, Su-Lin Lou, Yong-Yao Xie, Zhen-Lan Liu, Letian Chen and Yao-Guang Liu
Journal of Integrative Plant Biology 2013 55(2): 122-130
Published Online: November 28, 2012
DOI: 10.1111/jipb.12000

Plant mutants are important bio-resources for crop breeding and gene functional studies. Conventional methods for generating mutant libraries by mutagenesis of seeds with physical or chemical agents are of low efficiency. Here, we developed a highly-efficient ethyl methanesulfonate (EMS) mutagenesis system based on suspension-cultured cells, with rice (Oryza sativa L.) as an example. We show that treatment of suspension-cultured tiny cell clusters with 0.4% EMS for 18–22 h followed by differentiation and regeneration produced as high as 29.4% independent mutant lines with visible phenotypic variations, including a number of important agronomic traits such as grain size, panicle size, grain or panicle shape, tiller number and angle, heading date, male sterility, and disease sensitivity. No mosaic mutant was observed in the mutant lines tested. In this mutant library, we obtained a mutant with an abnormally elongated uppermost internode. Sequencing and functional analysis revealed that this is a new allelic mutant of eui (elongated uppermost internode) caused by two point mutations in the first exon of the EUI gene, representing a successful example of this mutagenesis system.

Chen YL, Liang HL, Ma XL, Lou SL, Xie YY, Liu ZL, Chen LT, Liu YG (2013) An efficient rice mutagenesis system based on suspension-cultured cells. J. Integr. Plant Biol. 55(2), 122–130.

Abstract (Browse 1673)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
An Image Skeletonization-Based Tool for Pollen Tube Morphology Analysis and Phenotyping  
Author: Chaofeng Wang, Cai-Ping Gui, Hai-Kuan Liu, Dong Zhang and Axel Mosig
Journal of Integrative Plant Biology 2013 55(2): 131-141
Published Online: December 5, 2012
DOI: 10.1111/j.1744-7909.2012.01184.x

The mechanism underlying pollen tube growth involves diverse genes and molecular pathways. Alterations in the regulatory genes or pathways cause phenotypic changes reflected by cellular morphology, which can be captured using fluorescence microscopy. Determining and classifying pollen tube morphological phenotypes in such microscopic images is key to our understanding the involvement of genes and pathways. In this context, we propose a computational method to extract quantitative morphological features, and demonstrate that these features reflect morphological differences relevant to distinguish different defects of pollen tube growth. The corresponding software tool furthermore includes a novel semi-automated image segmentation approach, allowing to highly accurately identify the boundary of a pollen tube in a microscopic image.

Wang C, Gui CP, Liu HK, Zhang D, Mosig A (2013) An image skeletonization-based tool for pollen tube morphology analysis and phenotyping. J. Integr. Plant Biol. 55(2), 131–141.

Abstract (Browse 1880)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
          Cell and Developmental Biology
Dynamic Actin Controls Polarity Induction de novo in Protoplasts
Author: Beatrix Zaban, Jan Maisch and Peter Nick
Journal of Integrative Plant Biology 2013 55(2): 142-159
Published Online: November 29, 2012
DOI: 10.1111/jipb.12001

Cell polarity and axes are central for plant morphogenesis. To study how polarity and axes are induced de novo, we investigated protoplasts of tobacco Nicotiana tabacum cv. BY-2 expressing fluorescently-tagged cytoskeletal markers. We standardized the system to such a degree that we were able to generate quantitative data on the temporal patterns of regeneration stages. The synthesis of a new cell wall marks the transition to the first stage of regeneration, and proceeds after a long preparatory phase within a few minutes. During this preparatory phase, the nucleus migrates actively, and cytoplasmic strands remodel vigorously. We probed this system for the effect of anti-cytoskeletal compounds, inducible bundling of actin, RGD-peptides, and temperature. Suppression of actin dynamics at an early stage leads to aberrant tripolar cells, whereas suppression of microtubule dynamics produces aberrant sausage-like cells with asymmetric cell walls. We integrated these data into a model, where the microtubular cytoskeleton conveys positional information between the nucleus and the membrane controlling the release or activation of components required for cell wall synthesis. Cell wall formation is followed by the induction of a new cell pole requiring dynamic actin filaments, and the new cell axis is manifested as elongation growth perpendicular to the orientation of the aligned cortical microtubules.

Zaban B, Maisch J, Nick P (2013) Dynamic actin controls polarity induction de novo in protoplasts. J. Integr. Plant Biol. 55(2), 142–159.

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          Metabolism and Biochemistry
Analyses of a Glycine max Degradome Library Identify microRNA Targets and MicroRNAs that Trigger Secondary SiRNA Biogenesis
Author: Zheng Hu, Qiyan Jiang, Zhiyong Ni, Rui Chen, Shuo Xu and Hui Zhang
Journal of Integrative Plant Biology 2013 55(2): 160-176
Published Online: February 4, 2013
DOI: 10.1111/jipb.12002

Plant microRNAs (miRNAs) regulate gene expression mainly by guiding cleavage of target mRNAs. In this study, a degradome library constructed from different soybean (Glycine max (L.) Merr.) tissues was deep-sequenced. 428 potential targets of small interfering RNAs and 25 novel miRNA families were identified. A total of 211 potential miRNA targets, including 174 conserved miRNA targets and 37 soybean-specific miRNA targets, were identified. Among them, 121 targets were first discovered in soybean. The signature distribution of soybean primary miRNAs (pri-miRNAs) showed that most pri-miRNAs had the characteristic pattern of Dicer processing. The biogenesis of TAS3 small interfering RNAs (siRNAs) was conserved in soybean, and nine Auxin Response Factors were identified as TAS3 siRNA targets. Twenty-three miRNA targets produced secondary small interfering RNAs (siRNAs) in soybean. These targets were guided by five miRNAs: gma-miR393, gma-miR1508, gma-miR1510, gma-miR1514, and novel-11. Multiple targets of these secondary siRNAs were detected. These 23 miRNA targets may be the putative novel TAS genes in soybean. Global identification of miRNA targets and potential novel TAS genes will contribute to research on the functions of miRNAs in soybean.

Hu Z, Jiang Q, Ni Z, Chen R, Xu S, Zhang H (2013) Analyses of a Glycine max degradome library identify microRNA targets and microRNAs that trigger secondary SiRNA biogenesis. J. Integr. Plant Biol. 55(2), 160–176.

Abstract (Browse 1531)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
          Plant-environmental Interactions
Identification and Characterization of the Populus AREB/ABF Subfamily
Author: Lexiang Ji, Jia Wang, Meixia Ye, Ying Li, Bin Guo, Zhong Chen, Hao Li and Xinmin An
Journal of Integrative Plant Biology 2013 55(2): 177-186
Published Online: February 4, 2013
DOI: 10.1111/j.1744-7909.2012.01183.x

Abscisic acid (ABA) is a major plant hormone that plays an important role in responses to abiotic stresses. The ABA-responsive element binding protein/ABRE-binding factor (AREB/ABF) gene subfamily contains crucial transcription factors in the ABA-mediated signaling pathway. In this study, a total of 14 putative AREB/ABF members were identified in the Populus trichocarpa Torr. & Gray. genome using five AREB/ABF amino acid sequences from Arabidopsis thaliana L. as probes. The 14 putative Populus subfamily members showed high protein similarities, especially in the basic leucine zipper (bZIP) domain region. A neighbor-joining analysis combined with gene structure data revealed homology among the 14 genes. The expression patterns of the Populus AREB/ABF subfamily suggested that the most abundant transcripts of 11 genes occurred in leaf tissues, while two genes were most transcribed in root tissues. Significantly, eight Populus AREB/ABF gene members were upregulated after treatment with 100 μM exogenous ABA, while the other six members were downregulated. We identified the expression profiles of the subfamily members in Populus tissues and elucidated different response patterns of Populus AREB/ABF members to ABA stress. This study provided insight into the roles of Populus AREB/ABF homologues in plant response to abiotic stresses.

Ji L, Wang J, Ye M, Li Y, Guo B, Chen Z, Li H, An X (2013) Identification and characterization of the Populus AREB/ABF subfamily. J. Integr. Plant Biol. 55(2), 177–186.

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          Molecular Ecology and Evolution
Narboh D, a Respiratory Burst Oxidase Homolog in Nicotiana attenuata, is Required for Late Defense Responses After Herbivore Attack  
Author: Jinsong Wu, Lei Wang, Hendrik Wüsche and Ian T. Baldwin
Journal of Integrative Plant Biology 2013 55(2): 187-198
Published Online: February 4, 2013
DOI: 10.1111/j.1744-7909.2012.01182.x

The superoxide (O2)-generating NADPH oxidases are crucial for the defense of plants against attack from pathogens; however, it remains unknown whether they also mediate responses against chewing insect herbivores. The transcripts of the respiratory burst NADPH oxidase homolog Narboh D in Nicotiana attenuate are rapidly and transiently elicited by wounding, and are amplified when Manduca sexta oral secretions (OS) are added to the wounds. The fatty-acid-amino-acid-conjugates (FACs), demonstrably the major elicitors in M. sexta OS, are responsible for the increase in Narboh D transcripts. Silencing Narboh D significantly reduced reactive oxygen species (ROS) levels after OS elicitation, but neither OS-elicited jasmonic acid (JA) or JA-isoleucine (JA-Ile) bursts, pivotal hormones that regulates plant resistance to herbivores, nor early transcripts of herbivore defense-related genes (NaJAR4 and NaPAL1), were influenced. However, late OS-elicited increases in trypsin proteinase inhibitors (TPIs), as well as the transcript levels of defense genes such as polyphenol oxidase, TPI and Thionin were significantly reduced. In addition, Narboh D-silenced plants were more vulnerable to insect herbivores, especially the larvae of the generalist Spodoptera littoralis. We thus conclude that Narboh D-based defenses play an important role in late herbivore-elicited responses.

Wu J, Wang L, W¨unsche H, Baldwin IT (2013) Narboh D, a respiratory burst oxidase homolog in Nicotiana attenuata, is required for late defense responses after herbivore attack. J. Integr. Plant Biol. 55(2), 187–198.

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