February 2017, Volume 59 Issue 2, Pages 77每153.


Cover Caption: Temperature sensing in clock
Circadian functions in plant's adaptation to diurnal temperature cycles and freezing tolerance. In this issue, Wang et al. (pp. 78每85) show that COR27 and COR28 facilitate a trade-off between freezing tolerance and flowering time. During chilling, COR27 and COR28 repress the accumulation of clock-associated transcripts, whereas CCA1 binds directly to the regulatory elements of COR27 and COR28 and inhibits their expressions at lower temperature. Mengli Shi from NIBS did the initial design for the cover.

 

          Letter to the Editor
COR27 and COR28 encode nighttime repressors integrating Arabidopsis circadian clock and cold response  
Author: Peng Wang, Xuan Cui, Chunsheng Zhao, Liyan Shi, Guowei Zhang, Fenglong Sun, Xiaofeng Cao, Li Yuan, Qiguang Xie and Xiaodong Xu
Journal of Integrative Plant Biology 2017 59(2): 78每85
Published Online: December 19, 2016
DOI: 10.1111/jipb.12512
      
    

It was noted that circadian components function in plant adaptation to diurnal temperature cycles and freezing tolerance. Our genome-wide transcriptome analysis revealed that evening-phased COR27 and COR28 mainly repress the transcription of clock-associated evening genes PRR5, ELF4 and cold-responsive genes. Chromatin immunoprecipitation indicated that CCA1 is recruited to the site containing EE elements of COR27 and COR28 promoters in a temperature-dependent way. Further genetic analysis shows COR28 is essential for the circadian function of PRR9 and PRR7. Together, our results support a role of COR27 and COR28 as nighttime repressors integrating circadian clock and plant cold stress responses.

Abstract (Browse 335)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
COR27 and COR28 repress the transcription of evening-phased clock genes and cold-responsive genes, which is responsible for maintaining circadian rhythm, plant freezing tolerance and flowering time control. CCA1 directly regulates COR27 and COR28 rhythmic expression in a temperature-dependent manner. This indicates the essential roles of COR27 and COR28 in coordinating circadian clock and cold-stress signaling networks.
          Invited Expert Review
WRKY transcription factors in plant responses to stresses  
Author: Jingjing Jiang, Shenghui Ma, Nenghui Ye, Ming Jiang, Jiashu Cao and Jianhua Zhang
Journal of Integrative Plant Biology 2017 59(2): 86每101
Published Online: December 20, 2016
DOI: 10.1111/jipb.12513
      
    
The WRKY gene family is among the largest families of transcription factors (TFs) in higher plants. By regulating the plant hormone signal transduction pathway, these TFs play critical roles in some plant processes in response to biotic and abiotic stress. Various bodies of research have demonstrated the important biological functions of WRKY TFs in plant response to different kinds of biotic and abiotic stresses and working mechanisms. However, very little summarization has been done to review their research progress. Not just important TFs function in plant response to biotic and abiotic stresses, WRKY also participates in carbohydrate synthesis, senescence, development, and secondary metabolites synthesis. WRKY proteins can bind to W-box (TGACC (A/T)) in the promoter of its target genes and activate or repress the expression of downstream genes to regulate their stress response. Moreover, WRKY proteins can interact with other TFs to regulate plant defensive responses. In the present review, we focus on the structural characteristics of WRKY TFs and the research progress on their functions in plant responses to a variety of stresses.
Abstract (Browse 785)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
WRKY transcription factors are primary specific to plants. This review illuminated the function of WRKY transcription factors by analyzing its structural features and the mode of WRKY transcription factors involved in various stress response signals.
          Molecular Physiology
A novel tomato SUMO E3 ligase, SlSIZ1, confers drought tolerance in transgenic tobacco  
Author: Song Zhang, Kunyang Zhuang, Shiju Wang, Jinlian Lv, Na'na Ma and Qingwei Meng
Journal of Integrative Plant Biology 2017 59(2): 102每117
Published Online: December 20, 2016
DOI: 10.1111/jipb.12514
      
    

SUMOylation is an important post-translational modification process that regulates different cellular functions in eukaryotes. SIZ/PIAS-type SAP and Miz1 (SIZ1) proteins exhibit SUMO E3 ligase activity, which modulates SUMOylation. However, SIZ1 in tomato has been rarely investigated. In this study, a tomato SIZ1 gene (SlSIZ1) was isolated and its molecular characteristics and role in tolerance to drought stress are described. SlSIZ1 was up-regulated by cold, sodium chloride (NaCl), polyethylene glycol (PEG), hydrogen peroxide (H2O2) and abscisic acid (ABA), and the corresponding proteins were localized in the nucleus. The expression of SlSIZ1 in Arabidopsis thaliana (Arabidopsis) siz1-2 mutants partially complemented the phenotypes of dwarf, cold sensitivity and ABA hypersensitivity. SlSIZ1 also exhibited the activity of SUMO E3 ligase to promote the accumulation of SUMO conjugates. Under drought stress, the ectopic expression of SlSIZ1 in transgenic tobacco lines enhanced seed germination and reduced the accumulation of reactive oxygen species. SlSIZ1 overexpression conferred the plants with improved growth, high free proline content, minimal malondialdehyde accumulation and increased accumulation of SUMO conjugates. SlSIZ1 is a functional homolog of Arabidopsis SIZ1 with SUMO E3 ligase activity. Therefore, overexpression of SlSIZ1 enhanced the tolerance of transgenic tobacco to drought stress.

Abstract (Browse 698)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
The tomato gene SlSIZ1 was isolated and the SlSIZ1 protein was identified as a functional homolog of Arabidopsis SIZ1 with SUMO E3 ligase activity. Overexpression of SlSIZ1 can enhance the drought tolerance of transgenic tobacco by increasing the levels of SUMO conjugates and osmotic materials, and decreasing membrane damage from ROS.
          Plant-environmental Interactions
The precise regulation of different COR genes by individual CBF transcription factors in Arabidopsis thaliana  
Author: Yihao Shi, Jiaying Huang, Tianshu Sun, Xuefei Wang, Chenqi Zhu, Yuxi Ai and Hongya Gu
Journal of Integrative Plant Biology 2017 59(2): 118每133
Published Online: December 23, 2016
DOI: 10.1111/jipb.12515
      
    

The transcription factors CBF1/2/3 are reported to play a dominant role in the cold responsive network of Arabidopsis by directly regulating the expression levels of cold responsive (COR) genes. In this study, we obtained CRISPR/Cas9-mediated loss-of-function mutants of cbf1∼3. Over 3,000 COR genes identified by RNA-seq analysis showed a slight but significant change in their expression levels in the mutants compared to the wild-type plants after being treated at 4 °C for 12 h. The C-repeat (CRT) motif (5′-CCGAC-3′) was enriched in promoters of genes that were up-regulated by CBF2 and CBF3 but not in promoters of genes up-regulated by CBF1. These data suggest that CBF2 and CBF3 play a more important role in directing the cold response by regulating different sets of downstream COR genes. More than 2/3 of COR genes were co-regulated by two or three CBFs and were involved mainly in cellular signal transduction and metabolic processes; less than 1/3 of the genes were regulated by one CBF, and those genes up-regulated were enriched in cold-related abiotic stress responses. Our results indicate that CBFs play an important role in the trade-off between cold tolerance and plant growth through the precise regulation of COR genes in the complicated transcriptional network.

Abstract (Browse 284)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
The CBF-dependent pathway is a plant-specific response to low temperature. We obtained three single mutants in Arabidopsis thaliana lacking CBF1~3 respectively using CRISPR/Cas9 technology. The RNA-seq data indicated that each CBF regulated a different set of COR genes, which formed a complicated network in response to cold stress.
          Plant Reproduction Biology
GRAIN INCOMPLETE FILLING 2 regulates grain filling and starch synthesis during rice caryopsis development  
Author: Xiangjin Wei, Guiai Jiao, Haiyan Lin, Zhonghua Sheng, Gaoneng Shao, Lihong Xie, Shaoqing Tang, Qingguo Xu and Peisong Hu
Journal of Integrative Plant Biology 2017 59(2): 134每153
Published Online: December 13, 2016
DOI: 10.1111/jipb.12510
      
    

Rice grain filling determines grain weight, final yield and grain quality. Here, a rice defective grain filling mutant, gif2, was identified. Grains of gif2 showed a slower filling rate and a significant lower final grain weight and yield compared to wild-type. The starch content in gif2 was noticeably decreased and its physicochemical properties were also altered. Moreover, gif2 endosperm cells showed obvious defects in compound granule formation. Positional cloning identified GIF2 to encode an ADP-glucose pyrophosphorylase (AGP) large subunit, AGPL2; consequently, AGP enzyme activity in gif2 endosperms was remarkably decreased. GIF2 is mainly expressed in developing grains and the coded protein localizes in the cytosol. Yeast two hybrid assay showed that GIF2 interacted with AGP small subunits OsAGPS1, OsAGPS2a and OsAGPS2b. Transcript levels for granule-bound starch synthase, starch synthase, starch branching enzyme and starch debranching enzyme were distinctly elevated in gif2 grains. In addition, the level of nucleotide diversity of the GIF2 locus was extremely low in both cultivated and wild rice. All of these results suggest that GIF2 plays important roles in the regulation of grain filling and starch biosynthesis during caryopsis development, and that it has been preserved during selection throughout domestication of modern rice.

Abstract (Browse 257)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
A rice mutant, gif2, displays remarkable slower grain filling rate, obvious defects in endosperm compound starch granule formation and less grain weight. Our work suggests that GIF2 encodes a large subunit of ADP-glucose pyrophosphorylase and plays a key role in the regulation of grain filling and endosperm starch biosynthesis.
 

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