October 2016, Volume 58 Issue 10, Pages 817每869.


Cover Caption: Functions of RNA Modifications
More than 100 RNA modifications are known in animals and plants. In this issue, Burgess et al. (822每835) provide a general review of known biological functions of RNA modifications, and enzymes mediating these modifications in plants. The cover image summarizes how RNA modifications can add another layer of regulation to the transcriptome by remodeling local RNA structure.

 

          Letter to the Editor
Pollen size strongly correlates with stigma depth among Pedicularis species  
Author: Xiang-Ping Wang, Wen-Bin Yu, Shi-Guo Sun and Shuang-Quan Huang
Journal of Integrative Plant Biology 2016 58(10): 818每821
Published Online: March 15, 2016
DOI: 10.1111/jipb.12477
      
    

Darwin proposed that pollen size should be positively correlated with stigma depth rather than style length among species given that pollen tubes first enter the stigma autotrophically, then grow through the style heterotrophically. However, studies often show a positive relationship between pollen size and style length. Five floral traits were observed to be correlated among 42 bumblebee-pollinated Pedicularis species (Orobanchaceae) in which stigmas are distinct from styles. The phylogenetic independent contrast analysis revealed that pollen grain volume was more strongly correlated with stigma depth than with style length, consistent with Darwin's functional hypothesis between pollen size and stigma depth.

Abstract (Browse 647)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
It was often observed a positive correlation between pollen size and style length among different species. However, Darwin (1877) had proposed that pollen size should be positively correlated with stigma depth rather than style length, given that pollen tubes first enter the stigma autotrophically, thereafter grow through the style heterotrophically. We provide evidence in support of the Darwin*s hypothesis by surveying 42 Pedicularis species with the phylogenetic independent contrast analysis.
          Invited Expert Review
Deciphering the epitranscriptome: A green perspective  
Author: Alice Burgess, Rakesh David and Iain Robert Searle
Journal of Integrative Plant Biology 2016 58(10): 822每835
Published Online: May 12, 2016
DOI: 10.1111/jipb.12483
      
    

The advent of high-throughput sequencing technologies coupled with new detection methods of RNA modifications has enabled investigation of a new layer of gene regulation − the epitranscriptome. With over 100 known RNA modifications, understanding the repertoire of RNA modifications is a huge undertaking. This review summarizes what is known about RNA modifications with an emphasis on discoveries in plants. RNA ribose modifications, base methylations and pseudouridylation are required for normal development in Arabidopsis, as mutations in the enzymes modifying them have diverse effects on plant development and stress responses. These modifications can regulate RNA structure, turnover and translation. Transfer RNA and ribosomal RNA modifications have been mapped extensively and their functions investigated in many organisms, including plants. Recent work exploring the locations, functions and targeting of N6-methyladenosine (m6A), 5-methylcytosine (m5C), pseudouridine (Ψ), and additional modifications in mRNAs and ncRNAs are highlighted, as well as those previously known on tRNAs and rRNAs. Many questions remain as to the exact mechanisms of targeting and functions of specific modified sites and whether these modifications have distinct functions in the different classes of RNAs.

Abstract (Browse 593)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
With over 100 known RNA modifications, understanding the repertoire of RNA modifications will be a huge undertaking. This review summarizes what is known about RNA modifications. In Arabidopsis, RNA ribose modifications, base methylations and pseudouridylation are required for normal development and these modifications can regulate RNA structure, turnover and translation.
          Molecular Physiology
OsGRF4 controls grain shape, panicle length and seed shattering in rice  
Author: Pingyong Sun, Wuhan Zhang, Yihua Wang, Qiang He, Fu Shu, Hai Liu, Jie Wang, Jianmin Wang, Longping Yuan and Huafeng Deng
Journal of Integrative Plant Biology 2016 58(10): 836每847
Published Online: March 3, 2016
DOI: 10.1111/jipb.12473
      
    

Traits such as grain shape, panicle length and seed shattering, play important roles in grain yield and harvest. In this study, the cloning and functional analysis of PANICLE TRAITS 2 (PT2), a novel gene from the Indica rice Chuandali (CDL), is reported. PT2 is synonymous with Growth-Regulating Factor 4 (OsGRF4), which encodes a growth-regulating factor that positively regulates grain shape and panicle length and negatively regulates seed shattering. Higher expression of OsGRF4 is correlated with larger grain, longer panicle and lower seed shattering. A unique OsGRF4 mutation, which occurs at the OsmiRNA396 target site of OsGRF4, seems to be associated with high levels of OsGRF4 expression, and results in phenotypic difference. Further research showed that OsGRF4 regulated two cytokinin dehydrogenase precursor genes (CKX5 and CKX1) resulting in increased cytokinin levels, which might affect the panicle traits. High storage capacity and moderate seed shattering of OsGRF4 may be useful in high-yield breeding and mechanized harvesting of rice. Our findings provide additional insight into the molecular basis of panicle growth.

Abstract (Browse 793)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
A novel rice gene PT2 is cloned, which is synonymous with Growth-Regulating Factor 4 (OsGRF4). It positively regulates grain shape, panicle length and negatively regulates seed shattering in rice. A unique mutation at the target site of OsmiRNA396 in OsGRF4 may enhance the expression of OsGRF4, resulting in phenotypic difference.
A bestrophin-like protein modulates the proton motive force across the thylakoid membrane in Arabidopsis  
Author: Zhikun Duan, Fanna Kong, Lin Zhang, Wenjing Li, Jiao Zhang and Lianwei Peng
Journal of Integrative Plant Biology 2016 58(10): 848每858
Published Online: March 7, 2016
DOI: 10.1111/jipb.12475
      
    

During photosynthesis, photosynthetic electron transport generates a proton motive force (pmf) across the thylakoid membrane, which is used for ATP biosynthesis via ATP synthase in the chloroplast. The pmf is composed of an electric potential (ΔΨ) and an osmotic component (ΔpH). Partitioning between these components in chloroplasts is strictly regulated in response to fluctuating environments. However, our knowledge of the molecular mechanisms that regulate pmf partitioning is limited. Here, we report a bestrophin-like protein (AtBest), which is critical for pmf partitioning. While the ΔpH component was slightly reduced in atbest, the ΔΨ component was much greater in this mutant than in the wild type, resulting in less efficient activation of nonphotochemical quenching (NPQ) upon both illumination and a shift from low light to high light. Although no visible phenotype was observed in the atbest mutant in the greenhouse, this mutant exhibited stronger photoinhibition than the wild type when grown in the field. AtBest belongs to the bestrophin family proteins, which are believed to function as chloride (Cl) channels. Thus, our findings reveal an important Cl channel required for ion transport and homeostasis across the thylakoid membrane in higher plants. These processes are essential for fine-tuning photosynthesis under fluctuating environmental conditions.

Abstract (Browse 566)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
This work describes a novel bestrophin-like chloride channel, AtBest, in chloroplasts. By mediating the influx of Cl into thylakoid lumen, AtBest directly modulates the partitioning of proton motive force across the thylakoid membrane. This kind of ion transport and homeostasis is essential for fine-tuning photosynthesis under fluctuating environmental conditions.
Abscisic acid and ethephon regulation of cellulase in the endosperm cap and radicle during lettuce seed germination  
Author: Bingxian Chen, Jun Ma, Zhenjiang Xu and Xiaofeng Wang
Journal of Integrative Plant Biology 2016 58(10): 859每869
Published Online: March 28, 2016
DOI: 10.1111/jipb.12479
      
    

The purpose of this study was to investigate the role of cellulase in endosperm cap weakening and radicle elongation during lettuce (Lactuca sativa L.) seed germination. The application of abscisic acid (ABA) or ethephon inhibits or promotes germination, respectively, by affecting endosperm cap weakening and radicle elongation. Cellulase activities, and related protein and transcript abundances of two lettuce cellulase genes, LsCEL1 and LsCEL2, increase in the endosperm cap and radicle prior to radicle protrusion following imbibition in water. ABA or ethephon reduce or elevate, respectively, cellulase activity, and related protein and transcript abundances in the endosperm cap. Taken together, these observations suggest that cellulase plays a role in endosperm cap weakening and radicle elongation during lettuce seed germination, and that the regulation of cellulase in the endosperm cap by ABA and ethephon play a role in endosperm cap weakening. However, the influence of ABA and ethephon on radicle elongation may not be through their effects on cellulase.

Abstract (Browse 671)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Cellulase activity, and related protein and transcript abundances of two lettuce cellulase genes, LsCEL1 and LsCEL2, were investigated in the endosperm cap and radicle during lettuce seed germination in water, ABA or ethephon. Our results suggested that cellulase plays a role in endosperm cap weakening and radicle elongation during germination.
 

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