December 2016, Volume 58 Issue 12, Pages 941每996.


Cover Caption: RLS3 Prevents Leaf Senescence
Senescence at the right time is important for crop yield. In this issue Lin et al. (pp.971每982) showed in rice that RLS3 plays a critical role in sustaining leaf longevity. RLS3 is expressed in various tissues, with the highest level in mesophyll cells. Overexpression of RLS3 prolonged leaf longevity and sustained normal growth, while loss of RLS3 function caused premature leaf senescence and retarded growth.

 

          Letter to the Editor
Loss of algal Proton Gradient Regulation 5 increases reactive oxygen species scavenging and H2 evolution  
Author: Mei Chen, Jin Zhang, Lei Zhao, Jiale Xing, Lianwei Peng, Tingyun Kuang, Jean-David Rochaix and Fang Huang
Journal of Integrative Plant Biology 2016 58(12): 943每946
Published Online: October 20, 2016
DOI: 10.1111/jipb.12502
      
    

We have identified hpm91, a Chlamydomonas mutant lacking Proton Gradient Regulation5 (PGR5) capable of producing hydrogen (H2) for 25 days with more than 30-fold yield increase compared to wild type. Thus, hpm91 displays a higher capacity of H2 production than a previously characterized pgr5 mutant. Physiological and biochemical characterization of hpm91 reveal that the prolonged H2 production is due to enhanced stability of PSII, which correlates with increased reactive oxygen species (ROS) scavenging capacity during sulfur deprivation. This anti-ROS response appears to protect the photosynthetic electron transport chain from photo-oxidative damage and thereby ensures electron supply to the hydrogenase.

Abstract (Browse 276)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
We identified and characterized a Chlamydomonas mutant (hpm91) lacking PGR5 which can produce H2 for 25 days with a more than 30-fold increase in yield as compared to wild type. This capacity exceeds that of another pgr5 mutant and qualifies hpm91 as the algal strain with the highest H2-photoproduction.
          Cell and Developmental Biology
Alternative splicing enhances transcriptome complexity in desiccating seeds  
Author: Arunkumar Srinivasan, Jos谷 M. Jim谷nez-G車mez, Fabio Fornara, Wim J. J. Soppe and Vittoria Brambilla
Journal of Integrative Plant Biology 2016 58(12): 947每958
Published Online: April 28, 2016
DOI: 10.1111/jipb.12482
      
    

Before being dispersed in the environment, mature seeds need to be dehydrated. The survival of seeds after dispersal depends on their low hydration in combination with high desiccation tolerance. These characteristics are established during seed maturation. Some key seed maturation genes have been reported to be regulated by alternative splicing (AS). However, so far AS was described only for single genes and a comprehensive analysis of AS during seed maturation has been lacking. We investigated gene expression and AS during Arabidopsis thaliana seed development at a global level, before and after desiccation. Bioinformatics tools were developed to identify differentially spliced regions within genes. Our data suggest the importance and shows the peculiar features of AS during seed desiccation. We identified AS in 34% of genes that are expressed at both timepoints before and after desiccation. Most of these AS transcript variants had not been found before in other tissues. Among the AS genes some seed master regulators could be found. Interestingly, 6% of all expressed transcripts were not transcriptionally regulated during desiccation, but only modified by AS. We propose that AS should be more routinely taken into account in the analysis of transcriptomic data to prevent overlooking potentially important regulators.

Abstract (Browse 469)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Dry seeds, that are important for plant reproduction and human nutrition, are produced after a critical seed desiccation phase. We studied genes expression and alternative splicing events at a genome level during this phase. Our findings show that many of the expressed genes are regulated by alternative splicing and that splicing could affect protein function.
Transcription factors AS1 and AS2 interact with LHP1 to repress KNOX genes in Arabidopsis  
Author: Zhongfei Li, Bin Li, Jian Liu, Zhihao Guo, Yuhao Liu, Yan Li, Wen-Hui Shen, Ying Huang, Hai Huang, Yijing Zhang and Aiwu Dong
Journal of Integrative Plant Biology 2016 58(12): 959每970
Published Online: July 20, 2016
DOI: 10.1111/jipb.12485
      
    

Polycomb group proteins are important repressors of numerous genes in higher eukaryotes. However, the mechanism by which Polycomb group proteins are recruited to specific genes is poorly understood. In Arabidopsis, LIKE HETEROCHROMATIN PROTEIN 1 (LHP1), also known as TERMINAL FLOWER 2, was originally proposed as a subunit of polycomb repressive complex 1 (PRC1) that could bind the tri-methylated lysine 27 of histone H3 (H3K27me3) established by the PRC2. In this work, we show that LHP1 mainly functions with PRC2 to establish H3K27me3, but not with PRC1 to catalyze monoubiquitination at lysine 119 of histone H2A. Our results show that complexes of the transcription factors ASYMMETRIC LEAVES 1 (AS1) and AS2 could help to establish the H3K27me3 modification at the chromatin regions of Class-I KNOTTED1-like homeobox (KNOX) genes BREVIPEDICELLUS and KNAT2 via direct interactions with LHP1. Additionally, our transcriptome analysis indicated that there are probably more common target genes of AS1 and LHP1 besides Class-I KNOX genes during leaf development in Arabidopsis.

Abstract (Browse 485)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
The transcription factors ASYMMETRIC LEAVES 1 (AS1) and AS2 directly interact with LIKE HETEROCHROMATIN PROTEIN 1 (LHP1), a reader protein of H3K27me3, and repress the expression of Class-I KNOX genes BP and KNAT2 via establishment of H3K27me3 modification during leaf development in Arabidopsis.
          Molecular Physiology
RLS3, a protein with AAA+ domain localized in chloroplast, sustains leaf longevity in rice
Author: Yanhui Lin, Lubin Tan, Lei Zhao, Xianyou Sun and Chuanqing Sun
Journal of Integrative Plant Biology 2016 58(12): 971每982
Published Online: June 30, 2016
DOI: 10.1111/jipb.12487
      
    

Leaf senescence plays an important role in crop developmental processes that dramatically affect crop yield and grain quality. The genetic regulation of leaf senescence is complex, involving many metabolic and signaling pathways. Here, we identified a rapid leaf senescence 3 (rls3) mutant that displayed accelerated leaf senescence, shorter plant height and panicle length, and lower seed set rate than the wild type. Map-based cloning revealed that RLS3 encodes a protein with AAA+ domain, localizing it to chloroplasts. Sequence analysis found that the rls3 gene had a single-nucleotide substitution (G[RIGHTWARDS ARROW]A) at the splice site of the 10th intron/11th exon, resulting in the cleavage of the first nucleotide in 11th exon and premature termination of RLS3 protein translation. Using transmission electron microscope, the chloroplasts of the rls3 mutant were observed to degrade much faster than those of the wild type. The investigation of the leaf senescence process under dark incubation conditions further revealed that the rls3 mutant displayed rapid leaf senescence. Thus, the RLS3 gene plays key roles in sustaining the normal growth of rice, while loss of function in RLS3 leads to rapid leaf senescence. The identification of RLS3 will be helpful to elucidate the mechanisms involved in leaf senescence in rice.

Abstract (Browse 410)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Leaf senescence is the final stage in plant development and associated with grain yield and plant quality. Here we isolated RLS3 gene, which delayed leaf senescence and restored grain yield in rice. Loss function of RLS3 gene caused growth retardation and grain yield reduction.
NARROW AND ROLLED LEAF 2 regulates leaf shape, male fertility, and seed size in rice
Author: Shuangshuang Zhao, Lei Zhao, Fengxia Liu, Yongzhen Wu, Zuofeng Zhu, Chuanqing Sun and Lubin Tan
Journal of Integrative Plant Biology 2016 58(12): 983每996
Published Online: October 20, 2016
DOI: 10.1111/jipb.12503
      
    

Grain yield in rice (Oryza sativa L.) is closely related to leaf and flower development. Coordinative regulation of leaf, pollen, and seed development in rice as a critical biological and agricultural question should be addressed. Here we identified two allelic rice mutants with narrow and semi-rolled leaves, named narrow and rolled leaf 2-1 (nrl2-1) and nrl2-2. Map-based molecular cloning revealed that NRL2 encodes a novel protein with unknown biochemical function. The mutation of NRL2 caused pleiotropic effects, including a reduction in the number of longitudinal veins, defective abaxial sclerenchymatous cell differentiation, abnormal tapetum degeneration and microspore development, and the formation of more slender seeds compared with the wild type (WT). The NRL2 protein interacted with Rolling-leaf (RL14), causing the leaves of the nrl2 mutants to have a higher cellulose content and lower lignin content than the WT, which may have been related to sclerenchymatous cell differentiation and tapetum degeneration. Thus, this gene is an essential developmental regulator controlling fundamental cellular and developmental processes, serving as a potential breeding target for high-yielding rice cultivars.

Abstract (Browse 357)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
NRL2 encodes a novel protein and plays numerous important roles during rice growth and development. Its mutation causes a reduction in the number of longitudinal veins, defective abaxial sclerenchymatous cell differentiation, abnormal tapetum degeneration and microspore development, and more slender seeds compared with the wild type.
 

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