February 2015, Volume 57 Issue 2, Pages 138每228.


Cover Caption: Cysteine Affects Root Stem Cells
Cysteine as well as sulfate inhibits primary root elongation in a dosage dependent manner. In this issue, Wang et al. (pp. 186每197) demonstrate that cysteine regulates the expressions of PLT1/2, SCR and SHR genes to maintain the stem cell niche in root meristem.

 

          Molecular Physiology
Arabidopsis transcriptional response to extracellular Ca2+ depletion involves a transient rise in cytosolic Ca2+
Author: Jing Wang, Tergel Tergel, Jianhua Chen, Ju Yang, Yan Kang and Zhi Qi
Journal of Integrative Plant Biology 2015 57(2): 138每150
Published Online: May 21, 2014
DOI: 10.1111/jipb.12218
      
    

Ecological evidence indicates a worldwide trend of dramatically decreased soil Ca2+ levels caused by increased acid deposition and massive timber harvesting. Little is known about the genetic and cellular mechanism of plants' responses to Ca2+ depletion. In this study, transcriptional profiling analysis helped identify multiple extracellular Ca2+ ([Ca2+]ext) depletion-responsive genes in Arabidopsis thaliana L., many of which are involved in response to other environmental stresses. Interestingly, a group of genes encoding putative cytosolic Ca2+ ([Ca2+]cyt) sensors were significantly upregulated, implying that [Ca2+]cyt has a role in sensing [Ca2+]ext depletion. Consistent with this observation, [Ca2+]ext depletion stimulated a transient rise in [Ca2+]cyt that was negatively influenced by [K+]ext, suggesting the involvement of a membrane potential-sensitive component. The [Ca2+]cyt response to [Ca2+]ext depletion was significantly desensitized after the initial treatment, which is typical of a receptor-mediated signaling event. The response was insensitive to an animal Ca2+ sensor antagonist, but was suppressed by neomycin, an inhibitor of phospholipase C. Gd3+, an inhibitor of Ca2+ channels, suppressed the [Ca2+]ext-triggered rise in [Ca2+]cyt and downstream changes in gene expression. Taken together, this study demonstrates that [Ca2+]cyt plays an important role in the putative receptor-mediated cellular and transcriptional response to [Ca2+]ext depletion of plant cells.

 

Wang J, Tergel T, Chen J, Yang J, Kang Y, Qi Z (2015) Arabidopsis transcriptional response to extracellular Ca2+ depletion involves a transient rise in cytosolic Ca2+. J Integr Plant Biol 57: 138–150. doi: 10.1111/jipb.12218

Abstract (Browse 940)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Animal cells have PLC-coupled Ca2+ receptor within the plasma membrane to sense extracellular Ca2+ concentration increase. In this study, we provide cellular evidence that arabidopsis root cells might have similar mechanism to sense extracellular Ca2+ decrease linked with cytosolic Ca2+ and downstream gene expression.
Identification and characterization of Mini1, a gene regulating rice shoot development
Author: Yunxia Fang, Jiang Hu, Jie Xu, Haiping Yu, Zhenyuan Shi, Guosheng Xiong, Li Zhu, Dali Zeng, Guangheng Zhang, Zhenyu Gao, Guojun Dong, Meixian Yan, Longbiao Guo, Yonghong Wang and Qian Qian
Journal of Integrative Plant Biology 2015 57(2): 151每161
Published Online: June 19, 2014
DOI: 10.1111/jipb.12230
      
    

The aerial parts of higher plants are generated from the shoot apical meristem (SAM). In this study, we isolated a small rice (Oryza sativa L.) mutant that showed premature termination of shoot development and was named mini rice 1 (mini1). The mutant was first isolated from a japonica cultivar Zhonghua11 (ZH11) subjected to ethyl methanesulfonate (EMS) treatment. With bulked segregant analysis (BSA) and map-based cloning method, Mini1 gene was finally fine-mapped to an interval of 48.6 kb on chromosome 9. Sequence analyses revealed a single base substitution from G to A was found in the region, which resulted in an amino acid change from Gly to Asp. The candidate gene Os09g0363900 was predicted to encode a putative adhesion of calyx edges protein ACE (putative HOTHEAD precursor) and genetic complementation experiment confirmed the identity of Mini1. Os09g0363900 contains glucose-methanol-choline (GMC) oxidoreductase and NAD(P)-binding Rossmann-like domain, and exhibits high similarity to Arabidopsis HOTHEAD (HTH). Expression analysis indicated Mini1 was highly expressed in young shoots but lowly in roots and the expression level of most genes involved in auxin biosynthesis and signal transduction were reduced in mutant. We conclude that Mini1 plays an important role in maintaining SAM activity and promoting shoot development in rice.

 

Fang Y, Hu J, Xu J, Yu H, Shi Z, Xiong G, Zhu L, Zeng D, Zhang G, Gao Z, Dong G, Yan M, Guo L, Wang Y, Qian Q (2015) Identification and characterization of Mini1, a gene regulating rice shoot development. J Integr Plant Biol 57: 151–161. doi: 10.1111/jipb.12230

Abstract (Browse 1223)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
The aerial part of higher plants is generated from the shoot apical meristem (SAM). A mini rice mutant (mini1), which shows premature termination of shoot development, was identified and characterized. Mini1 encodes a putative adhesion of calyx edges protein and play an important role in maintaining SAM activity in rice.
Structural and functional analysis of an asymmetric bidirectional promoter in Arabidopsis thaliana
Author: Shi-Juan Liu, Qiu-Juan Yue and Wei Zhang
Journal of Integrative Plant Biology 2015 57(2): 162每170
Published Online: November 4, 2014
DOI: 10.1111/jipb.12308
      
    

Bidirectional promoters are relatively abundant in eukaryotic genomes, suggesting that they have an important biological significance. As yet, few of these promoters have been characterized in detail. Here, using a promoter::GUS transgene approach has revealed that the intergenic region of Arabidopsis thaliana divergent genes At1g71850 and At1g71860 is an asymmetric bidirectional promoter, which exhibits an orientation-dependent expression profile. The strength of the forward promoter was greater than that of the reverse promoter, and their tissue specificities were not identical. Deletion analyses revealed that this bidirectional promoter could be divided into three functional regions. The basal level and tissue specificity of the promoter in the reverse orientation were regulated positively by region II and negatively by region III, whereas promoter activity in the forward orientation was regulated negatively by region II and positively by region I. Thus the 52-bp stretch of region II had a dual function, enhancing expression in the reverse orientation and suppressing it in the forward orientation. These results demonstrated that the activity of the At1g71850-At1g71860 bidirectional promoter was modulated by complex interactions between both positive and negative cis-acting elements. These findings will enhance our understanding of the regulatory mechanisms of plant bidirectional promoters.

 

Liu SJ, Yue QJ and Zhang W (2015) Structural and functional analysis of an asymmetric bidirectional promoter in Arabidopsis thaliana. J Integr Plant Biol 57: 162–170. doi: 10.1111/jipb.12308

Abstract (Browse 938)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Bidirectional promoters are with unique ability in controlling the expression of divergent gene pairs. The intergenic region of Arabidopsis At1g71850 and At1g71860 is a functional bidirectional promoter, which controls the asymmetric expression of the gene pair in both directions by using orientation-dependent positive and negative cis-elements.
K+ retention in leaf mesophyll, an overlooked component of salinity tolerance mechanism: A case study for barley  
Author: Honghong Wu, Min Zhu, Lana Shabala, Meixue Zhou and Sergey Shabala
Journal of Integrative Plant Biology 2015 57(2): 171每185
Published Online: July 6, 2014
DOI: 10.1111/jipb.12238
      
    

Plant salinity tolerance is a physiologically complex trait, with numerous mechanisms contributing to it. In this work, we show that the ability of leaf mesophyll to retain K+ represents an important and essentially overlooked component of a salinity tolerance mechanism. The strong positive correlation between mesophyll K+ retention ability under saline conditions (quantified by the magnitude of NaCl-induced K+ efflux from mesophyll) and the overall salinity tolerance (relative fresh weight and/or survival or damage under salinity stress) was found while screening 46 barley (Hordeum vulgare L.) genotypes contrasting in their salinity tolerance. Genotypes with intrinsically higher leaf K+ content under control conditions were found to possess better K+ retention ability under salinity and, hence, overall higher tolerance. Contrary to previous reports for barley roots, K+ retention in mesophyll was not associated with an increased H+-pumping in tolerant varieties but instead correlated negatively with this trait. These findings are explained by the fact that increased H+ extrusion may be needed to charge balance the activity and provide the driving force for the high affinity HAK/KUP K+ transporters required to restore cytosolic K+ homeostasis in salt-sensitive genotypes.

 

Wu H, Zhu M, Shabala L, Zhou M, Shabala S (2015) K+ retention in leaf mesophyll, an overlooked component of salinity tolerance mechanism: A case study for barley. J Integr Plant Biol 57: 171–185. doi: 10.1111/jipb.12238

Abstract (Browse 1198)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
This work reports strong positive correlation between barley mesophyll K+ retention ability under saline conditions (quantified by the magnitude of NaCl-induced K+ efflux from mesophyll) and the overall salinity tolerance and suggests that the above trait represents an important and essentially overlooked component of a salinity tolerance mechanism in plants.
          Plant-environmental Interactions
L-Cysteine inhibits root elongation through auxin/PLETHORA and SCR/SHR pathway in Arabidopsis thaliana
Author: Zhen Wang, Jie-Li Mao, Ying-Jun Zhao, Chuan-You Li and Cheng-Bin Xiang
Journal of Integrative Plant Biology 2015 57(2): 186每197
Published Online: May 5, 2014
DOI: 10.1111/jipb.12213
      
    

L-Cysteine plays a prominent role in sulfur metabolism of plants. However, its role in root development is largely unknown. Here, we report that L-cysteine reduces primary root growth in a dosage-dependent manner. Elevating cellular L-cysteine level by exposing Arabidopsis thaliana seedlings to high L-cysteine, buthionine sulphoximine, or O-acetylserine leads to altered auxin maximum in root tips, the expression of quiescent center cell marker as well as the decrease of the auxin carriers PIN1, PIN2, PIN3, and PIN7 of primary roots. We also show that high L-cysteine significantly reduces the protein level of two sets of stem cell specific transcription factors PLETHORA1/2 and SCR/SHR. However, L-cysteine does not downregulate the transcript level of PINs, PLTs, or SCR/SHR, suggesting that an uncharacterized post-transcriptional mechanism may regulate the accumulation of PIN, PLT, and SCR/SHR proteins and auxin transport in the root tips. These results suggest that endogenous L-cysteine level acts to maintain root stem cell niche by regulating basal- and auxin-induced expression of PLT1/2 and SCR/SHR. L-Cysteine may serve as a link between sulfate assimilation and auxin in regulating root growth.

 

Wang Z, Mao JL, Zhao YJ, Li CY, Xiang CB (2015) L坼Cysteine inhibits root elongation through auxin/PLETHORA and SCR/SHR pathway in Arabidopsis thaliana. J Integr Plant Biol 57: 186–197 doi: 10.1111/jipb.12213

Abstract (Browse 942)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
L-Cysteine is essential amino acid. However, its role in root development is largely unknown. This study shows that L-cysteine reduces primary root growth in a dosage-dependent manner through maintaining root stem cell niche by regulating basal- and auxin-induced expression of PLT1/2 and SCR/SHR.
Cytokinin levels and signaling respond to wounding and the perception of herbivore elicitors in Nicotiana attenuata  
Author: Martin Schäfer, Ivan D. Meza-Canales, Aura Navarro-Quezada, Christoph Brütting, Radomira Vanková, Ian T. Baldwin and Stefan Meldau
Journal of Integrative Plant Biology 2015 57(2): 198每212
Published Online: June 13, 2014
DOI: 10.1111/jipb.12227
      
    

Nearly half a century ago insect herbivores were found to induce the formation of green islands by manipulating cytokinin (CK) levels. However, the response of the CK pathway to attack by chewing insect herbivores remains unclear. Here, we characterize the CK pathway of Nicotiana attenuata (Torr. ex S. Wats.) and its response to wounding and perception of herbivore-associated molecular patterns (HAMPs). We identified 44 genes involved in CK biosynthesis, inactivation, degradation, and signaling. Leaf wounding rapidly induced transcriptional changes in multiple genes throughout the pathway, as well as in the levels of CKs, including isopentenyladenosine and cis-zeatin riboside; perception of HAMPs present in the oral secretions (OS) of the specialist herbivore Manduca sexta amplified these responses. The jasmonate pathway, which triggers many herbivore-induced processes, was not required for these HAMP-triggered changes, but rather suppressed the CK responses. Interestingly CK pathway changes were observed also in systemic leaves in response to wounding and OS application indicating a role of CKs in mediating long distance systemic processes in response to herbivory. Since wounding and grasshopper OS elicited similar accumulations of CKs in Arabidopsis thaliana L., we propose that CKs are integral components of wounding and HAMP-triggered responses in many plant species.

 

Schäfer M, Meza坼Canales ID, Navarro坼Quezada A, Brütting C, Vanková R, Baldwin IT, Meldau S (2015) Cytokinin levels and signaling respond to wounding and the perception of herbivore elicitors in Nicotiana attenuata. J Integr Plant Biol 57: 198–212. doi: 10.1111/jipb.12227

Abstract (Browse 1153)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
Cytokinins, classical plant growth regulators, were found to be induced after herbivory in the wild tobacco. The response was wound-induced, but also dependent on elicitors which present in oral secretions of tobacco hornworm caterpillars. The changes were not dependent on, but modified by jasmonates. Similar responses were also observed in arabidopsis.
OsHK3 is a crucial regulator of abscisic acid signaling involved in antioxidant defense in rice  
Author: Feng Wen, Tingting Qin, Yao Wang, Wen Dong, Aying Zhang, Mingpu Tan and Mingyi Jiang
Journal of Integrative Plant Biology 2015 57(2): 213每228
Published Online: June 9, 2014
DOI: 10.1111/jipb.12222
      
    

In this study, the role of the rice (Oryza sativa L.) histidine kinase OsHK3 in abscisic acid (ABA)-induced antioxidant defense was investigated. Treatments with ABA, H2O2, and polyethylene glycol (PEG) induced the expression of OsHK3 in rice leaves, and H2O2 is required for ABA-induced increase in the expression of OsHK3 under water stress. Subcellular localization analysis showed that OsHK3 is located in the cytoplasm and the plasma membrane. The transient expression analysis and the transient RNA interference test in rice protoplasts showed that OsHK3 is required for ABA-induced upregulation in the expression of antioxidant enzymes genes and the activities of antioxidant enzymes. Further analysis showed that OsHK3 functions upstream of the calcium/calmodulin-dependent protein kinase OsDMI3 and the mitogen-activated protein kinase OsMPK1 to regulate the activities of antioxidant enzymes in ABA signaling. Moreover, OsHK3 was also shown to regulate the expression of nicotinamide adenine dinucleotide phosphate oxidase genes, OsrbohB and OsrbohE, and the production of H2O2 in ABA signaling. Our data indicate that OsHK3 play an important role in the regulation of ABA-induced antioxidant defense and in the feedback regulation of H2O2 production in ABA signaling.

 

Wen F, Qin T, Wang Y, Dong W, Zhang A, Tan M, Jiang M (2015) OsHK3 is a crucial regulator of abscisic acid signaling involved in antioxidant defense in rice. J Integr Plant Biol 57: 213–228. doi: 10.1111/jipb.12222

Abstract (Browse 1230)  |  References  |  Full Text HTML  |  Full Text PDF  |  Cited By       
This study finds that the rice histidine kinase OsHK3 plays important roles in the regulation of abscisic acid (ABA)-induced antioxidant defense and in the feedback regulation of H2O2 production in ABA signaling.
 

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