August 2018, Volume 60 Issue 8, Pages 625-736.


Cover Caption: Leaf stage¨Cassociated resistance to pathogens
Leaf stage©\associated resistance is not much known before. In this issue, Xu et al. (pp.703¨C722) reported the existence of leaf stage©\associated basal resistance, which is correlated with phytohormones such as salicylic acid, ethylene, jasmonic acid and abscisic acid in a pathosystem©\dependent manner. The resistance is linked to substantial alteration in defense©\related gene expression.

 

          Letter to the Editor
Multiplex gene editing in rice with simplified CRISPR©\Cpf1 and CRISPR©\Cas9 systems  
Author: Mugui Wang, Yanfei Mao, Yuming Lu, Zhidan Wang, Xiaoping Tao and Jian-Kang Zhu
Journal of Integrative Plant Biology 2018 60(8): 626-631
Published Online: May 15, 2018
DOI: 10.1111/jipb.12667
      
    

We developed simplified single transcriptional unit (SSTU) CRISPR systems for multiplex gene editing in rice using FnCpf1, LbCpf1 or Cas9, in which the nuclease and its crRNA array are co©\expressed from a single Pol II promoter, without any additional processing machinery. Our SSTU systems are easy to construct and effective in mediating multiplex genome editing.

Abstract (Browse 579)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
We developed the simplified single transcriptional unit (SSTU) CRISPR systems for multiplex gene editing in rice using FnCpf1, LbCpf1 or Cas9, in which the nuclease and its crRNA array are co©\expressed from single Pol II promoter, without any additional processing machinery. SSTU systems are simple and effective in multiplex genome editing.
          Invited Expert Reviews
Hormone modulation of legume©\rhizobial symbiosis
Author: Huan Liu, Chi Zhang, Jun Yang, Nan Yu and Ertao Wang
Journal of Integrative Plant Biology 2018 60(8): 632-648
Published Online: March 26, 2018
DOI: 10.1111/jipb.12653
      
    

Leguminous plants can establish symbiotic associations with diazotropic rhizobia to form nitrogen©\fixating nodules, which are classified as determinate or indeterminate based on the persistence of nodule meristem. The formation of nitrogen©\fixing nodules requires coordinating rhizobial infection and root nodule organogenesis. The formation of an infection thread and the extent of nodule formation are largely under plant control, but vary with environmental conditions and the physiological state of the host plants. Many achievements in these two areas have been made in recent decades. Phytohormone signaling pathways have gradually emerged as important regulators of root nodule symbiosis. Cytokinin, strigolactones (SLs) and local accumulation of auxin can promote nodule development. Ethylene, jasmonic acid (JA), abscisic acid (ABA) and gibberellic acid (GA) all negatively regulate infection thread formation and nodule development. However, salicylic acid (SA) and brassinosteroids (BRs) have different effects on the formation of these two nodule types. Some peptide hormones are also involved in nodulation. This review summarizes recent findings on the roles of these plant hormones in legume©\rhizobial symbiosis, and we propose that DELLA proteins may function as a node to integrate plant hormones to regulate nodulation.

Abstract (Browse 228)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Legumes establish symbiotic associations with rhizobia to form nitrogen©\fixating nodules. Phytohormones have been confirmed as important regulators in this process. We summarized recent findings about the roles of plant hormones and some small peptides in legume©\rhizobial symbiosis, and proposed that DELLA proteins function as a node in the regulatory network.
Plant glycosylphosphatidylinositol anchored proteins at the plasma membrane©\cell wall nexus
Author: Trevor H. Yeats, Antony Bacic and Kim L. Johnson
Journal of Integrative Plant Biology 2018 60(8): 649-669
Published Online: April 18, 2018
DOI: 10.1111/jipb.12659
      
    

Approximately 1% of plant proteins are predicted to be post©\translationally modified with a glycosylphosphatidylinositol (GPI) anchor that tethers the polypeptide to the outer leaflet of the plasma membrane. Whereas the synthesis and structure of GPI anchors is largely conserved across eukaryotes, the repertoire of functional domains present in the GPI©\anchored proteome has diverged substantially. In plants, this includes a large fraction of the GPI©\anchored proteome being further modified with plant©\specific arabinogalactan (AG) O©\glycans. The importance of the GPI©\anchored proteome to plant development is underscored by the fact that GPI biosynthetic null mutants exhibit embryo lethality. Mutations in genes encoding specific GPI©\anchored proteins (GAPs) further supports their contribution to diverse biological processes, occurring at the interface of the plasma membrane and cell wall, including signaling, cell wall metabolism, cell wall polymer cross©\linking, and plasmodesmatal transport. Here, we review the literature concerning plant GPI©\anchored proteins, in the context of their potential to act as molecular hubs that mediate interactions between the plasma membrane and the cell wall, and their potential to transduce the signal into the protoplast and, thereby, activate signal transduction pathways.

Abstract (Browse 161)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
GPI anchors attach proteins to the outer leaflet of the plasma membrane. Although well characterised in mammals and yeast, less is known about the biosynthesis and structure of GPI anchors in plants. In this review, we cover the importance of plant GPI©\anchored proteins at the plasma membrane©\cell wall interface.
          Metabolism and Biochemistry
Characterization of maize leaf pyruvate orthophosphate dikinase using high throughput sequencing  
Author: Yuling Zhang, Rita Giuliani, Youjun Zhang, Yang Zhang, Wagner Luiz Araujo, Baichen Wang, Peng Liu, Qi Sun, Asaph Cousins, Gerald Edwards, Alisdair Fernie, Thomas P. Brutnell and Pinghua Li
Journal of Integrative Plant Biology 2018 60(8): 670-690
Published Online: April 17, 2018
DOI: 10.1111/jipb.12656
      
    

In C4 photosynthesis, pyruvate orthophosphate dikinase (PPDK) catalyzes the regeneration of phosphoenolpyruvate in the carbon shuttle pathway. Although the biochemical function of PPDK in maize is well characterized, a genetic analysis of PPDK has not been reported. In this study, we use the maize transposable elements Mutator and Ds to generate multiple mutant alleles of PPDK. Loss©\of©\function mutants are seedling lethal, even when plants were grown under 2% CO2, and they show very low capacity for CO2 assimilation, indicating C4 photosynthesis is essential in maize. Using RNA©\seq and GC©\MS technologies, we examined the transcriptional and metabolic responses to a deficiency in PPDK activity. These results indicate loss of PPDK results in downregulation of gene expression of enzymes of the C4 cycle, the Calvin cycle, and components of photochemistry. Furthermore, the loss of PPDK did not change Kranz anatomy, indicating that this metabolic defect in the C4 cycle did not impinge on the morphological differentiation of C4 characters. However, sugar metabolism and nitrogen utilization were altered in the mutants. An interaction between light intensity and genotype was also detected from transcriptome profiling, suggesting altered transcriptional and metabolic responses to environmental and endogenous signals in the PPDK mutants.

Abstract (Browse 567)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Pyruvate orthophosphate dikinase (PPDK) is a key enzyme in the C4 carbon shuttle pathway. Using RNA©\seq and GC©\MS technologies, we examined the transcriptional and metabolic responses to deficiency of PPDK activity. Loss of PPDK affects the pathways of C4 cycle, calvin cycle, sugar metabolism and nitrogen utilization.
          Molecular Physiology
bHLH104 confers tolerance to cadmium stress in Arabidopsis thaliana
Author: Xiani Yao, Yuerong Cai, Diqiu Yu, Gang Liang
Journal of Integrative Plant Biology 2018 60(8): 691-702
Published Online: April 18, 2018
DOI: 10.1111/jipb.12658
      
    

Cd is a non©\essential heavy metal that is toxic to both plants and animals. Here, we reveal that the transcription factor bHLH104 positively regulates Cd tolerance in Arabidopsis thaliana. We show that Fe deficiency©\responsive genes were induced by Cd treatment, and that their upregulation was suppressed in bhlh104 loss©\of©\function mutants, but enhanced upon overexpression of bHLH104. Correspondingly, the bhlh104 mutants displayed sensitivity to Cd stress, whereas plants overexpressing bHLH104 exhibited enhanced Cd tolerance. Further analysis suggested that bHLH104 positively regulates four heavy metal detoxification©\associated genes, IREG2, MTP3, HMA3 and NAS4, which play roles in Cd sequestration and tolerance. The bHLH104 overexpression plants accumulated high levels of Cd in the root but low levels of Cd in the shoot, which might contribute to the Cd tolerance in those lines. The present study thus points to bHLH104 as a potentially useful tool for genetic engineering of plants with enhanced Cd tolerance.

Abstract (Browse 162)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
bHLH104 is a key regulator of iron homeostasis and also confers cadmium stress tolerance in plants. The elevated expression of bHLH104 causes the cadmium sequestration in roots, inhibits cadmium translocation from roots to shoots, and hence enhances cadmium tolerance in plants.
          Plant-biotic Interactions
Leaf stage©\associated resistance is correlated with phytohormones in a pathosystem©\dependent manner
Author: You-Ping Xu, Lin-Hui Lv, Ya-Jing Xu, Juan Yang, Jia-Yi Cao and Xin-Zhong Cai
Journal of Integrative Plant Biology 2018 60(8): 703-722
Published Online: April 28, 2018
DOI: 10.1111/jipb.12661
      
    

It has been reported in several pathosystems that disease resistance can vary in leaves at different stages. However, how general this leaf stage©\associated resistance is, and the molecular mechanism(s) underlying it, remain largely unknown. Here, we investigated the effect of leaf stage on basal resistance, effector©\triggered immunity (ETI) and nonhost resistance, using eight pathosystems involving the hosts Arabidopsis thaliana, Nicotiana tabacum, and N. benthamiana and the pathogens Sclerotinia sclerotiorum, Pseudomonas syringae pv. tabaci, P. syringae pv. tomato DC3000, and Xanthomonas oryzae pv. oryzae (Xoo). We show evidence that leaf stage©\associated resistance exists ubiquitously in plants, but with varying intensity at different stages in diverse pathosystems. Microarray expression profiling assays demonstrated that hundreds of genes involved in defense responses, phytohormone biosynthesis and signaling, and calcium signaling, were differentially expressed between leaves at different stages. The Arabidopsis mutants sid1, sid2©\3, ein2, jar1©\1, aba1 and aao3 lost leaf stage©\associated resistance to S. sclerotiorum, and the mutants aba1 and sid2©\3 were affected in leaf stage©\associated RPS2/AvrRpt2+©\conferred ETI, whereas only the mutant sid2©\3 influenced leaf stage©\associated nonhost resistance to Xoo. Our results reveal that the phytohormones salicylic acid, ethylene, jasmonic acid and abscisic acid likely play an essential, but pathosystem©\dependent, role in leaf stage©\associated resistance.

Abstract (Browse 140)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Various types of leaf stage©\associated resistance exist ubiquitously in plants, but with varying intensity at different stages in diverse pathosystems. Phytohormones such as salicylic acid, ethylene, jasmonic acid and abscisic acid likely play essential but pathosystem©\dependent roles in leaf stage©\associated resistance.
          Plant Reproduction Biology
Arabidopsis thaliana NOP10 is required for gametophyte formation
Author: Lin-Xiao Li, Hong-Ze Liao, Li-Xi Jiang, Qing Tan, De Ye and Xue-Qin Zhang
Journal of Integrative Plant Biology 2018 60(8): 723-736
Published Online: March 26, 2018
DOI: 10.1111/jipb.12652
      
    

The female gametophyte is crucial for sexual reproduction of higher plants, yet little is known about the molecular mechanisms underlying its development. Here, we report that Arabidopsis thaliana NOP10 (AtNOP10) is required for female gametophyte formation. AtNOP10 was expressed predominantly in the seedling and reproductive tissues, including anthers, pollen grains, and ovules. Mutations in AtNOP10 interrupted mitosis of the functional megaspore during early development and prevented polar nuclear fusion in the embryo sacs. AtNOP10 shares a high level of amino acid sequence similarity with Saccharomyces cerevisiae (yeast) NOP10 (ScNOP10), an important component of the H/ACA small nucleolar ribonucleoprotein particles (H/ACA snoRNPs) implicated in 18S rRNA synthesis and rRNA pseudouridylation. Heterologous expression of ScNOP10 complemented the mutant phenotype of Atnop10. Thus, AtNOP10 influences functional megaspore mitosis and polar nuclear fusion during gametophyte formation in Arabidopsis.

Abstract (Browse 195)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
AtNOP10 is required for female gametophyte formation, and its mutations interrupt mitosis of the functional megaspore during early development and prevent polar nuclear fusion in embryo sacs. AtNOP10 may be a key component of H/ACA snoRNPs implicated in 18S rRNA synthesis and rRNA pseudouridylation which are involved in female gametophyte development.
 

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