August 2016, Volume 58 Issue 8, Pages 697¨C758.


Cover Caption: Evolution of Long Tubed Flowers
It has been accepted that the evolution of long-tubed flowers is driven by long-tongued pollinators. However, numerous Pedicularis species in Himalayas evolve long corolla tubes but are pollinated by bumblebees. As shown on the cover that corolla tubes in P. siphonantha from southwest China are up to 10 cm in length. Huang et al. (pp. 698¨C700) manipulated the length of the corolla tube to examine pollinator preference and seed set, data obtained do not support the traditional hypothesis. Photo provided by Shuang-Quan Huang.

 

          Letters to the Editor
Are long corolla tubes in Pedicularis driven by pollinator selection?  
Author: Shuang-Quan Huang, Xiang-Ping Wang and Shi-Guo Sun
Journal of Integrative Plant Biology 2016 58(8): 698-700
Published Online: December 30, 2015
DOI: 10.1111/jipb.12460
      
    

The evolution of long corolla tubes has been hypothesized to be driven by long-tongued pollinators. Corolla tubes in Pedicularis species can be longer than 10 cm which may function as flower stalks to increase visual attractiveness to pollinators because these species provide no nectar and are pollinated by bumblebees. The corolla tube length was manipulated (shorter or longer) in two Pedicularis species in field to examine whether longer tubes are more attractive to pollinators and produce more seeds than short tubes. Our results did not support the pollinator attraction hypothesis, leaving the evolution of long tubes in Pedicularis remains mysterious.

Abstract (Browse 684)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
The evolution of long corolla tubes in Pedicularis species seems to break a classic Ħ°arms raceĦħ model between plants and pollinators. Quantifying manipulated corolla tube length and fitness in two Pedicularis species indicated that longer tubes were not more attractive to pollinators with more seeds than short tubes.
The wheat MYB-related transcription factor TaMYB72 promotes flowering in rice  
Author: Lichao Zhang, Guoxiang Liu, Jizeng Jia, Guangyao Zhao, Chuan Xia, Lina Zhang, Fu Li, Qiang Zhang, Chunhao Dong, Shuangcheng Gao, Longzhi Han, Xiuping Guo, Xin Zhang, Jinxia Wu, Xu Liu and Xiuying Kong
Journal of Integrative Plant Biology 2016 58(8): 701-704
Published Online: December 30, 2015
DOI: 10.1111/jipb.12461
      
    
Through large-scale transformation analyses, TaMYB72 was identified as a flowering time regulator in wheat. TaMYB72 is a MYB family transcription factor localized to the nucleus. Three TaMYB72 homologs, TaMYB72-A, TaMYB72-B and TaMYB72-D, cloned from hexaploid wheat were mapped to the short arm of the group 6 chromosomes. Under the long-day conditions, over-expression of the TaMYB72 in rice shortened the flowering time by approximately 12 d. Expression analyses suggest that TaMYB72 may function through up-regulation of florigen genes Hd3a and RFT1.

 

 

Abstract (Browse 781)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
TaMYB72 has been identified as flowering time regulator in wheat. TaMYB72 encoded a MYB family transcription factor localized to the nucleus. Over-expression of TaMYB72 in rice shortened the flowering time by approximately 12 days. Expression analyses suggested that TaMYB72 may function through the up-regulation of rice florigen genes Hd3a and RFT1.
          New Technology
A simple, flexible and high-throughput cloning system for plant genome editing via CRISPR-Cas system
Author: Hyeran Kim, Sang-Tae Kim, Jahee Ryu, Min Kyung Choi, Jiyeon Kweon, Beum-Chang Kang, Hyo-Min Ahn, Suji Bae, Jungeun Kim, Jin-Soo Kim and Sang-Gyu Kim
Journal of Integrative Plant Biology 2016 58(8): 705-712
Published Online: March 4, 2016
DOI: 10.1111/jipb.12474
      
    

CRISPR-Cas9 system is now widely used to edit a target genome in animals and plants. Cas9 protein derived from Streptococcus pyogenes (SpCas9) cleaves double-stranded DNA targeted by a chimeric single-guide RNA (sgRNA). For plant genome editing, Agrobacterium-mediated T-DNA transformation has been broadly used to express Cas9 proteins and sgRNAs under the control of CaMV 35S and U6/U3 promoter, respectively. We here developed a simple and high-throughput binary vector system to clone a 19−20 bp of sgRNA, which binds to the reverse complement of a target locus, in a large T-DNA binary vector containing an SpCas9 expressing cassette. Two-step cloning procedures: (1) annealing two target-specific oligonucleotides with overhangs specific to the AarI restriction enzyme site of the binary vector; and (2) ligating the annealed oligonucleotides into the two AarI sites of the vector, facilitate the high-throughput production of the positive clones. In addition, Cas9-coding sequence and U6/U3 promoter can be easily exchanged via the GatewayTM system and unique EcoRI/XhoI sites on the vector, respectively. We examined the mutation ratio and patterns when we transformed these constructs into Arabidopsis thaliana and a wild tobacco, Nicotiana attenuata. Our vector system will be useful to generate targeted large-scale knock-out lines of model as well as non-model plant.

Abstract (Browse 541)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
          Functional Omics and Systems Biology
Transcriptome analysis of near-isogenic lines provides molecular insights into starch biosynthesis in maize kernel  
Author: Yingni Xiao, Shawn Thatcher, Min Wang, Tingting Wang, Mary Beatty, Gina Zastrow-Hayes, Lin Li, Jiansheng Li, Bailin Li and Xiaohong Yang
Journal of Integrative Plant Biology 2016 58(8): 713-723
Published Online: December 17, 2015
DOI: 10.1111/jipb.12455
      
    

Starch is the major component in maize kernels, providing a stable carbohydrate source for humans and livestock as well as raw material for the biofuel industry. Increasing maize kernel starch content will help meet industry demands and has the potential to increase overall yields. We developed a pair of maize near-isogenic lines (NILs) with different alleles for a starch quantitative trait locus on chromosome 3 (qHS3), resulting in different kernel starch content. To investigate the candidate genes for qHS3 and elucidate their effects on starch metabolism, RNA-Seq was performed for the developing kernels of the NILs at 14 and 21 d after pollination (DAP). Analysis of genomic and transcriptomic data identified 76 genes with nonsynonymous single nucleotide polymorphisms and 384 differentially expressed genes (DEGs) in the introgressed fragment, including a hexokinase gene, ZmHXK3a, which catalyzes the conversion of glucose to glucose-6-phosphate and may play a key role in starch metabolism. The expression pattern of all DEGs in starch metabolism shows that altered expression of the candidate genes for qHS3 promoted starch synthesis, with positive consequences for kernel starch content. These results expand the current understanding of starch biosynthesis and accumulation in maize kernels and provide potential candidate genes to increase starch content.

Abstract (Browse 599)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
The transcriptomic variation of the developing kernels at 14 and 21 DAP was explored between a pair of maize near-isogenic lines, which contains different alleles for a starch QTL on chromosome 3 (qHS3). The result shows that the altered expression level of the candidate genes for qHS3 may promote starch synthesis, with positive consequences for starch content.
Expression of the inactive ZmMEK1 induces salicylic acid accumulation and salicylic acid-dependent leaf senescence  
Author: Yuan Li, Ying Chang, Chongchong Zhao, Hailian Yang and Dongtao Ren
Journal of Integrative Plant Biology 2016 58(8): 724-736
Published Online: January 29, 2016
DOI: 10.1111/jipb.12465
      
    

Leaf senescence is the final leaf developmental process that is regulated by both intracellular factors and environmental conditions. The mitogen-activated protein kinase (MAPK) signaling cascades have been shown to play important roles in regulating leaf senescence; however, the component(s) downstream of the MAPK cascades in regulating leaf senescence are not fully understood. Here we showed that the transcriptions of ZmMEK1, ZmSIMK1, and ZmMPK3 were induced during dark-induced maize leaf senescence. Furthermore, in-gel kinase analysis revealed the 42 kDa MAPK was activated. ZmMEK1 interacted with ZmSIMK1 in yeast and maize mesophyll protoplasts and ZmSIMK1 was activated by ZmMEK1 in vitro. Expression of a dominant negative mutant of ZmMEK1 in Arabidopsis transgenic plants induced salicylic acid (SA) accumulation and SA-dependent leaf senescence. ZmMEK1 interacted with Arabidopsis MPK4 in yeast and activated MPK4 in vitro. SA treatment accelerated dark-induced maize leaf senescence. Moreover, blockage of MAPK signaling increased endogenous SA accumulation in maize leaves. These findings suggest that ZmMEK1-ZmSIMK1 cascade and its modulating SA levels play important roles in regulating leaf senescence.

Abstract (Browse 576)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
MAPK signaling cascades play important roles in regulating leaf senescence. We demonstrate that inactive ZmMEK1 induces SA accumulation and SA-dependent leaf senescence in its transgenic Arabidopsis plants. ZmMEK1 activates ZmSIMK1 and Arabidopsis MPK4 in vitro. Blockage of MAPK signaling increases endogenous SA accumulation in maize leaves.
          Molecular Physiology
Mitochondrial GPX1 silencing triggers differential photosynthesis impairment in response to salinity in rice plants
Author: Yugo Lima-Melo, Fabricio E. L. Carvalho, Márcio O. Martins, Gisele Passaia, Rachel H. V. Sousa, Milton C. Lima Neto, Márcia Margis-Pinheiro and Joaquim A. G. Silveira
Journal of Integrative Plant Biology 2016 58(8): 737-748
Published Online: January 22, 2016
DOI: 10.1111/jipb.12464
      
    

The physiological role of plant mitochondrial glutathione peroxidases is scarcely known. This study attempted to elucidate the role of a rice mitochondrial isoform (GPX1) in photosynthesis under normal growth and salinity conditions. GPX1 knockdown rice lines (GPX1s) were tested in absence and presence of 100 mM NaCl for 6 d. Growth reduction of GPX1s line under non-stressful conditions, compared with non-transformed (NT) plants occurred in parallel to increased H2O2 and decreased GSH contents. These changes occurred concurrently with photosynthesis impairment, particularly in Calvin cycle's reactions, since photochemical efficiency did not change. Thus, GPX1 silencing and downstream molecular/metabolic changes modulated photosynthesis differentially. In contrast, salinity induced reduction in both phases of photosynthesis, which were more impaired in silenced plants. These changes were associated with root morphology alterations but not shoot growth. Both studied lines displayed increased GPX activity but H2O2 content did not change in response to salinity. Transformed plants exhibited lower photorespiration, water use efficiency and root growth, indicating that GPX1 could be important to salt tolerance. Growth reduction of GPX1s line might be related to photosynthesis impairment, which in turn could have involved a cross talk mechanism between mitochondria and chloroplast originated from redox changes due to GPX1 deficiency.

Abstract (Browse 717)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Glutathione peroxidases (GPX) are a gene family constituted by five members in rice plants. GPX1 is an isoform localized in mitochondria and its physiological function is scarcely known. In this paper we demonstrated that GPX1 is important to photosynthesis under normal growth and salinity conditions.
Identification and functional characterization of the AGO1 ortholog in maize  
Author: Dongdong Xu, Hailong Yang, Cheng Zou, Wen-Xue Li, Yunbi Xu and Chuanxiao Xie
Journal of Integrative Plant Biology 2016 58(8): 749-758
Published Online: February 5, 2016
DOI: 10.1111/jipb.12467
      
    

Eukaryotic Argonaute proteins play primary roles in miRNA and siRNA pathways that are essential for numerous developmental and biological processes. However, the functional roles of the four ZmAGO1 genes have not yet been characterized in maize (Zea mays L.). In the present study, ZmAGO1a was identified from four putative ZmAGO1 genes for further characterization. Complementation of the Arabidopsis ago1-27 mutant with ZmAGO1a indicated that constitutive overexpression of ZmAGO1a could restore the smaller rosette, serrated leaves, later flowering and maturation, lower seed set, and darker green leaves at late stages of the mutant to the wild-type phenotype. The expression profiles of ZmAGO1a under five different abiotic stresses indicated that ZmAGO1a shares expression patterns similar to those of Argonaute genes in rice, Arabidopsis, and wheat. Further, variation in ZmAGO1a alleles among diverse maize germplasm that resulted in several amino acid changes revealed genetic diversity at this locus. The present data suggest that ZmAGO1a might be an important AGO1 ortholog in maize. The results presented provide further insight into the function of ZmAGO1a.

Abstract (Browse 642)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Argonaute proteins play primary roles in miRNA and siRNA pathways that are essential for numerous developmental and biological processes in plants. The functional complementation study and expression profiling analysis demonstrated that ZmAGO1a was an important AGO1 ortholog in maize (Zea mays L.).
 

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