July 2016, Volume 58 Issue 7, Pages 613每692.


Cover Caption: The Role of TMEM18 in Arabidopsis
TMEM18 proteins are conserved in most eukaryotes, and may associate with obesity in human. In this issue, Dou et al. (pp.679每692) showed that the Arabidopsis TMEM18 (AtTMEM18) is localized around nuclei and plays important roles in plant growth. Mutation in AtTMEM18 affected callose deposition, and caused defects in pollen tube growth.

 

          Letters to the Editor
Shade-induced stem elongation in rice seedlings: Implication of tissue-specific phytohormone regulation  
Author: Huihui Liu, Chuanwei Yang and Lin Li
Journal of Integrative Plant Biology 2016 58(7): 614每617
Published Online: February 17, 2016
DOI: 10.1111/jipb.12468
      
    

A better understanding of shade avoidance syndrome (SAS) is an urgent need because of its effect on energy reallocation. Leverage-related mechanism in crops is of potential economic interest for agricultural applications. Here we report the SAS phenotype at tissue level rice seedlings. Tissue-specific RNA-sequencing indicates auxin plays different roles between coleoptile and the first leaf. Phenotypes of wild type treated by gibberellin and brassinosteroid biosynthesis inhibitors and of related mutants suggest these two hormones positively regulate SAS. Our work reveals the diversity of hormone responses in different organs and different species in shade conditions.

Abstract (Browse 769)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
The authors grow rice seedlings in simulated shade which mimic the seedlings grown in high density, and characterize the phenotype and global transcriptome changes. This work suggests that hormone inhibitors, such as PAC, can help form compact and sturdy seedlings without compromising growth in paddy fields.
Depletion of tyrosyl-DNA phosphodiesterase 1汐 (MtTdp1汐) affects transposon expression in Medicago truncatula  
Author: Maria Elisa Sabatini, Mattia Donà, Paola Leonetti, Andrea Minio, Massimo Delledonne, Daniela Carbonera, Massimo Confalonieri, Giorgio Giraffa and Alma Balestrazzi
Journal of Integrative Plant Biology 2016 58(7): 618每622
Published Online: December 23, 2015
DOI: 10.1111/jipb.12457
      
    

The role of plant tyrosyl-DNA phosphodiesterase 1α in genome stability is studied using a Medicago truncatula MtTdp1α-depleted line. Lack of MtTdp1α results in a 39% reduction of methylated cytosines as compared to control. RNA-Seq analyses revealed that 11 DNA transposons and 22 retrotransposons were differentially expressed in the Tdp1α-2a line. Among them all, DNA transposons (MuDR, hAT, DNA3-11_Mad) and seven retrotransposons (LTR (Long Terminal Repeat)/Gipsy, LTR/Copia, LTR and NonLTR/L1) were down-regulated, while the 15 retrotransposons were up-regulated. Results suggest that the occurrence of stress-responsive cis-elements as well as changes in the methylation pattern at the LTR promoters might be responsible for the enhanced retrotransposon transcription.

Abstract (Browse 629)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Cellulose synthesis genes CESA6 and CSI1 are important for salt stress tolerance in Arabidopsis  
Author: Shuang-Shuang Zhang, Le Sun, Xinran Dong, Sun-Jie Lu, Weidong Tian and Jian-Xiang Liu
Journal of Integrative Plant Biology 2016 58(7): 623每626
Published Online: October 27, 2015
DOI: 10.1111/jipb.12442
Abstract (Browse 953)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Two salt hypersensitive mutants she1 and she2 were identified through genetic screening. SHE1 encodes a cellulose synthase CESA6 while SHE2 encodes a cellulose synthase-interactive protein CSI1. Both of them are involved in cellulose deposition. Our results demonstrated that the sustained cellulose synthesis is important for salt stress tolerance in Arabidopsis.
          Cell and Developmental Biology
Putative zeatin O-glucosyltransferase OscZOG1 regulates root and shoot development and formation of agronomic traits in rice
Author: Xiao-Ling Shang, Rong-Rong Xie, Hua Tian, Qing-Long Wang and Fang-Qing Guo
Journal of Integrative Plant Biology 2016 58(7): 627每641
Published Online: October 28, 2015
DOI: 10.1111/jipb.12444
      
    

As a ubiquitous reaction, glucosylation controls the bioactivity of cytokinins in plant growth and development. Here we show that genetic manipulation of zeatin-O-glucosylation regulates the formation of important agronomic traits in rice by manipulating the expression of OscZOG1 gene, encoding a putative zeatin O-glucosyltransferase. We found that OscZOG1 was preferentially expressed in shoot and root meristematic tissues and nascent organs. The growth of lateral roots was stimulated in the overexpression lines, but inhibited in RNA interference lines. In shoots, knockdown of OscZOG1 expression by RNA interference significantly improved tillering, panicle branching, grain number per panicle and seed size, which are important agronomic traits for grain yield. In contrast, constitutive expression of OscZOG1 leads to negative effects on the formation of the grain-yielding traits with a marked increase in the accumulation levels of cis-zeatin O-glucoside (cZOG) in the transgenic rice plants. In this study, our findings demonstrate the feasibility of improving the critical yield-determinant agronomic traits, including tiller number, panicle branches, total grain number per panicle and grain weight by downregulating the expression level of OscZOG1. Our results suggest that modulating the levels of cytokinin glucosylation can function as a fine-tuning switch in regulating the formation of agronomic traits in rice.

Abstract (Browse 820)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
This study demonstrated the feasibility of improving the critical yield-determinant agronomic traits by down-regulating the expression level of OscZOG1. The results revealed a novel mechanism in which modulating the levels of cytokinin glucosylation can function as a fine-tuning switch in regulating the formation of agronomic traits in rice.
          Plant-environmental Interactions
DELLA proteins interact with FLC to repress flowering transition  
Author: Mingzhe Li, Fengying An, Wenyang Li, Mengdi Ma, Ying Feng, Xing Zhang and Hongwei Guo
Journal of Integrative Plant Biology 2016 58(7): 642每655
Published Online: November 20, 2015
DOI: 10.1111/jipb.12451
      
    

Flowering is a highly orchestrated and extremely critical process in a plant's life cycle. Previous study has demonstrated that SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) and FLOWERING LOCUS T (FT) integrate the gibberellic acid (GA) signaling pathway and vernalization pathway in regulating flowering time, but detailed molecular mechanisms remain largely unclear. In GA signaling pathway, DELLA proteins are a group of master transcriptional regulators, while in vernalization pathway FLOWERING LOCUS C (FLC) is a core transcriptional repressor that down-regulates the expression of SOC1 and FT. Here, we report that DELLA proteins interact with FLC in vitro and in vivo, and the LHRI domains of DELLAs and the C-terminus of MADS domain of FLC are required for these interactions. Phenotypic and gene expression analysis showed that mutation of FLC reduces while over-expression of FLC enhances the GA response in the flowering process. Further, DELLA-FLC interactions promote the repression ability of FLC on its target genes. In summary, these findings report that the interaction between MADS box transcription factor FLC and GRAS domain regulator DELLAs may integrate various signaling inputs in flowering time control, and shed new light on the regulatory mechanism both for FLC and DELLAs in regulating gene expression.

Abstract (Browse 1218)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
The authors reveal a mechanism underlying GA pathway and vernalization pathway in regulating flowering time: GRAS domain regulator DELLAs directly interact with MADS box transcription factor FLC and enhance the repression ability of FLC on its target genes which is required for floral transition.
Shifting Nicotiana attenuata's diurnal rhythm does not alter its resistance to the specialist herbivore Manduca sexta
Author: Jasmin Herden, Stefan Meldau, Sang-Gyu Kim, Grit Kunert, Youngsung Joo, Ian T. Baldwin and Meredith C. Schuman
Journal of Integrative Plant Biology 2016 58(7): 656每668
Published Online: December 23, 2015
DOI: 10.1111/jipb.12458
      
    

Arabidopsis thaliana plants are less resistant to attack by the generalist lepidopteran herbivore Trichoplusia ni when plants and herbivores are entrained to opposite, versus identical diurnal cycles and tested under constant conditions. This effect is associated with circadian fluctuations in levels of jasmonic acid, the transcription factor MYC2, and glucosinolate contents in leaves. We tested whether a similar effect could be observed in a different plant–herbivore system: the wild tobacco Nicotiana attenuata and its co-evolved specialist herbivore, Manduca sexta. We measured larval growth on plants under both constant and diurnal conditions following identical or opposite entrainment, profiled the metabolome of attacked leaf tissue, quantified specific metabolites known to reduce M. sexta growth, and monitored M. sexta feeding activity under all experimental conditions. Entrainment did not consistently affect M. sexta growth or plant defense induction. However, both were reduced under constant dark conditions, as was M. sexta feeding activity. Our data indicate that the response induced by M. sexta in N. attenuata is robust to diurnal cues and independent of plant or herbivore entrainment. We propose that while the patterns of constitutive or general damage-induced defense may undergo circadian fluctuation, the orchestration of specific induced responses is more complex.

Abstract (Browse 559)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Living things have internal circadian clocks to coordinate with external diurnal cycles. Circadian fluctuations in plant defense can provide resistance to herbivory when plants and herbivores share a diurnal cycle. However for a plant which responds strongly and specifically to a co-evolved herbivore, plant resistance was independent of diurnal cycle.
          Plant Reproduction Biology
The Arabidopsis CROWDED NUCLEI genes regulate seed germination by modulating degradation of ABI5 protein  
Author: Wenming Zhao, Chunmei Guan, Jian Feng, Yan Liang, Ni Zhan, Jianru Zuo and Bo Ren
Journal of Integrative Plant Biology 2016 58(7): 669每678
Published Online: November 13, 2015
DOI: 10.1111/jipb.12448
      
    

In Arabidopsis, the phytohormone abscisic acid (ABA) plays a vital role in inhibiting seed germination and in post-germination seedling establishment. In the ABA signaling pathway, ABI5, a basic Leu zipper transcription factor, has important functions in the regulation of seed germination. ABI5 protein localizes in nuclear bodies, along with AFP, COP1, and SIZ1, and was degraded through the 26S proteasome pathway. However, the mechanisms of ABI5 nuclear body formation and ABI5 protein degradation remain obscure. In this study, we found that the Arabidopsis CROWDED NUCLEI (CRWN) proteins, predicted nuclear matrix proteins essential for maintenance of nuclear morphology, also participate in ABA-controlled seed germination by regulating the degradation of ABI5 protein. During seed germination, the crwn mutants are hypersensitive to ABA and have higher levels of ABI5 protein compared to wild type. Genetic analysis suggested that CRWNs act upstream of ABI5. The observation that CRWN3 colocalizes with ABI5 in nuclear bodies indicates that CRWNs might participate in ABI5 protein degradation in nuclear bodies. Moreover, we revealed that the extreme C-terminal of CRWN3 protein is necessary for its function in the response to ABA in germination. Our results suggested important roles of CRWNs in ABI5 nuclear body organization and ABI5 protein degradation during seed germination.

Abstract (Browse 1413)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
The authors found that the Arabidopsis CRWNs predicted nuclear matrix proteins, might participate in ABI5 protein degradation in nuclear bodies, and then regulate ABA-controlled seed germination. Moreover, the extreme C-terminal of CRWN3 protein is necessary for its function in the response to ABA in germination.
AtTMEM18 plays important roles in pollen tube and vegetative growth in Arabidopsis  
Author: Xiao-Ying Dou, Ke-Zhen Yang, Zhao-Xia Ma, Li-Qun Chen, Xue-Qin Zhang, Jin-Rong Bai and De Ye
Journal of Integrative Plant Biology 2016 58(7): 679每692
Published Online: December 24, 2015
DOI: 10.1111/jipb.12459
      
    

In flowering plants, pollen tube growth is essential for delivery of male gametes into the female gametophyte or embryo sac for double fertilization. Although many genes have been identified as being involved in the process, the molecular mechanisms of pollen tube growth remains poorly understood. In this study, we identified that the Arabidopsis Transmembrane Protein 18 (AtTMEM18) gene played important roles in pollen tube growth. The AtTMEM18 shares a high similarity with the Transmembrane 18 proteins (TMEM18s) that are conserved in most eukaryotes and may play important roles in obesity in humans. Mutation in the AtTMEM18 by a Ds insertion caused abnormal callose deposition in the pollen grains and had a significant impact on pollen germination and pollen tube growth. AtTMEM18 is expressed in pollen grains, pollen tubes, root tips and other vegetative tissues. The pollen-rescued assays showed that the mutation in AtTMEM18 also caused defects in roots, stems, leaves and transmitting tracts. AtTMEM18-GFP was located around the nuclei. Genetic assays demonstrated that the localization of AtTMEM18 around the nuclei in the generative cells of pollen grains was essential for the male fertility. Furthermore, expression of the rice TMEM18-homologous protein (OsTMEM18) driven by LAT52 promoter could recover the fertility of the Arabidopsis attmem18 mutant. These results suggested that the TMEM18 is important for plant growth in Arabidopsis.

Abstract (Browse 736)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
The Transmembrane 18 proteins (TMEM18s) are conserved in most eukaryotes and may be related to obesity in humans. This study shows that Arabidopsis TMEM18 (AtTMEM18) plays important roles in plant growth. Mutation in AtTMEM18 affected callose deposition and caused defects in pollen tube and other plant tissues.
 

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