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Volume 7 Special Issue 1 2013
Stress-Mediated Signaling in Plants II
ISBN 978-4-907060-08-4
How to reference: Sharma M, Pandey A, Pandey GK (2013) Role of Plant U-BOX (PUB) Protein in Stress and Development. In: Girdhar K. Pandey (Ed) Stress-Mediated Signaling in Plants II . Plant Stress 7 (Special Issue 1), 1-9
Guest Editor
Girdhar K. Pandey
CONTENTS AND ABSTRACTS
Manisha Sharma, Amita Pandey, Girdhar K. Pandey (India) Role of Plant U-BOX (PUB) Protein in Stress and Development (pp 1-9)
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ABSTRACT
Invited Review: During the past few years, the significance of regulated protein degradation has become increasingly apparent in plants. There has been a remarkable exploration of information on the proteins of the ubiquitin/proteasome system and their role in protein degradation throughout the eukaryotes. The proteasome ubiquitination system selects a number of proteins for post-translational modification and subsequently, subjects them to degradation. E3 ubiquitin ligases play a central role in determining the target specificity in this system. Interestingly, most recently discovered, RING/U-box represents a type of E3 ligases and shows greater prevalence in plants (PUBs, Plant U-box E3 ubiquitin ligases) in comparison to animals. Hence, suggesting their involvement in a range of indispensable processes in plant system. U-box is a highly conserved domain whose physiological function remains unclear, but it has been implicated as a regulator of fundamental cellular processes ranging from cellular growth, damage responses and apoptosis. Besides, on the basis of assorted accessory domains or protein binding motifs, PUBs can be classified into several subclasses, which bestow functional divergence to them. Moreover, genome wide homology searches in monocots and dicots have revealed similar domain organizations in several of the U-box genes suggesting their evolution through a common ancestor. The participation of PUBs in plant development is extensive, affecting processes related to development and signal transduction cascades. Moreover, increasing evidences points towards the association of PUBs in defense against biotic as well as abiotic stresses. Here, we will be emphasizing the current knowledge about the aspects of cellular responses shared by PUB proteins in plants under stress and developmental conditions.
Thiruvenkadam Shanmugam, Manisha Sharma, Amita Pandey, Girdhar K. Pandey (India) Small GTPases: Rho of Plant (ROP) in Development and Stress Signaling (pp 10-15)
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ABSTRACT
Invited Mini-Review: The small GTPase superfamily is comprised of four families (ROP, ARF, RAB and RAN) in the plant kingdom. The members of this superfamily show diversity in structure and function, despite possessing a conserved G-domain for GTP-binding and hydrolysis. ROP (Rho of Plants) has emerged as plant-specific GTPases to orchestrate unique cellular function such as polarity establishment, stress and plant hormonal signaling. The prominent role in their functional capability is evident from their varied expressional regulation in different developmental and stress conditions. The functional activity of small GTPases is tuned by both positive (guanine exchange factor, GEF) and negative regulators (Guanine Dissociation Inhibitor, GDI and GTPase activating protein, GAP), which favors the ON and OFF state of small GTPases, respectively. The expressional variation of regulators as well as their spatial and temporal expression pattern determine the activity and hence turn-on the switch of small GTPases. In this report, we are exploring the expressional and functional analysis of ROP class of small GTPases in plants under stress and developmental signaling pathways.
Annapurna Bhattacharjee, Mukesh Jain (India) Transcription Factor-Mediated Abiotic Stress Signaling in Rice (pp 16-25)
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ABSTRACT
Invited Mini-Review: Abiotic stresses are the major cause that limits productivity of crop plants worldwide. Plants respond to these stress conditions at physiological and molecular levels. At the molecular level, the expression of thousands of genes is altered in response to various abiotic stress conditions. Several studies have been performed to find out the role of these genes in abiotic stress signaling. However, among these, transcription factor encoding genes are most important because many of them act as ‘key or master regulators’ of gene expression. Transcription factors appear to be attractive targets to unravel the molecular mechanisms of abiotic stress responses and engineering abiotic stress tolerance in plants. However, the role of only a few transcription factors in abiotic stress responses have been elucidated in rice until now and require a detailed investigation for several such candidate genes. In this review, our endeavour is to develop a comprehensive understanding of the intricate regulatory network of transcription factors operative during abiotic stress responses with greater emphasis on rice.
Alka Shankar, Amita Pandey, Girdhar K. Pandey (India) WRKY Transcription Factor: Role in Abiotic and Biotic Stress (pp 26-34)
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ABSTRACT
Invited Review: One of the fundamental behaviors of plants, being sessile allows them to develop an intricate molecular machinery to adapt themselves to biotic and abiotic challenges experienced in the environment. In response to adapt against a particular stress, a massive transcriptional activity of several genes triggered the defense responses in the plant cell. Extensive research on stress related studies have introduced the role of transcription factors for regulation of the plants responses. In many cases, transcription factors acts as a “master or key regulator” of gene expression under one or multiple stress conditions. In plants, WRKY has emerged as a major and largest transcription factor family. Arabidopsis and rice has 74 and 109 WRKY members respectively, which play a major role during stress and development. WRKY gene family has been studied to be induced in response to several phytohormones such as SA, JA, ABA and pathogen attack, thus have been found to be a key player in plant defense mechanism. This gene family also forms a highly interacting regulatory network with stress response, by acting as either transcription activator or repressor thereby modulating the gene expression. Beside stress and developmental conditions, WRKY is also induced in nutrient deficient conditions such as phosphate deficiency and starvation. The main emphasis of this review is to summarize the progress in WRKY transcription factor research under stress and developmental conditions. At the same time an attempt has also been made to comment upon interaction with a wide range of signaling networks such as MAP kinase proteins, 14-3-3 proteins, calmodulin and regulator of chromatin such as histone deacetylases, and plant-pathogen defense proteins. Moreover, a crosstalk or overlap is also discussed among these different components or pathways involving WRKY transcription factor.
Pradipto Mukhopadhyay, Sneh Lata Singla-Pareek, Malireddy Kondandarami Reddy, Sudhir Kumar Sopory (India) Regulation of Stress Responsive Genes in Plants: Involvement of Epigenetic Mechanisms (pp 35-46)
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ABSTRACT
Invited Review: Plants, being sessile, have developed a myriad of strategies to withstand the unavoidable stresses, which otherwise by no means can be escaped. These mechanisms involve complex cellular machineries operating in a web of signal transduction. Repertoires of genes are either up- or down- regulated during various phases of stress signaling, the understanding of whose regulation is still mesmerizing. In recent times, batteries of epigenetic mechanisms have been found to operate underneath the discovered roles of transcription factors and cis-elements. These epigenetic mechanisms involving DNA methylation, histone modifiers and ATP-dependent chromatin remodelers are the ones that directly influence the transcription of genes in eukaryotes. In the present review, the discovered and speculative roles of these epigenetic mechanisms in the regulation of stress responsive genes will be discussed and areas will be determined which needs to be focused in order to understand global stress specific gene regulation and to engineer better stress tolerant plants.
Dhirendra Kumar, Tazley Hotz, Mir Hossain, Pavan Chigurupati, Amukta Mayakoti, Nkongho Binda, Bingqing Zhao, Diwaker Tripathi (USA) Methyl Salicylate Esterases in Plant Immunity (pp 47-51)
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ABSTRACT
Invited Mini-Review: Salicylic acid (SA) is an important signal in various plant processes. It is well known and widely studied for its role in plant disease resistance. Several proteins, which physically interact with SA has been identified and characterized for their possible role in disease resistance signaling. These plant proteins bind to SA with varying affinity and they differ considerably in their structure and activity. The protein, which binds to SA with highest affinity amongst all the characterized SA-binding proteins, is SABP2. It is a 29-kDa protein and has esterase like enzymatic activity. It is able to use plant synthesized methyl salicylate as a substrate and convert it into SA, which triggers disease resistance in plants. Silencing of SABP2 makes plants more susceptible to pathogens and their capacity to induce SAR is severely compromised. The esterase activity of SABP2 is required to process the phloem mobile signal, MeSA in distal uninoculated tissues to induce resistance. The binding of SA to SABP2 is important for activation of SAR in distal tissues.
Alok Pandey, Subhadeep Chaterjee (India) Signaling in Plant-Microbe Interactions (pp 52-59)
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ABSTRACT
Invited Review: Plants are attacked by different kinds of pathogens; therefore plants have evolved defense mechanism to combat the pathogen attack and diseases. Many microbial signature molecules, which are known as microbe associated or pathogen associated molecular patterns (MAMPs/PAMPs) are recognized by a plant’s primary layer of immune response, known as PAMP-triggered immunity (PTI). In the co-evolution of plant-microbe interactions, successful pathogens have acquired the ability to deliver effectors proteins directly inside plant cell to suppress PTI, allowing pathogen growth and disease. As a counter measure, plants have developed a second layer of defense system, by acquiring the ability to recognize these effector proteins via ‘Resistance’ (R) protein to trigger a defense response, known as effector triggered immunity (ETI). In this review, we discuss the developments that have taken place in understanding the PTI, effectors function, ETI and downstream signaling events. Understanding plant immune signaling pathways would be very helpful in controlling plant diseases.
Khirod K. Sahoo, Amit K. Tripathi, Ashwani Pareek, Sneh L. Singla-Pareek (India) Taming Drought Stress in Rice through Genetic Engineering of Transcription Factors and Protein Kinases (pp 60-72)
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ABSTRACT
Invited Mini-Review: The majority of the world’s population depends on rice as the principal staple food crop. Water deficit or drought stress is one of the serious environmental threats and the main constraint to rice productivity. It affects rice at morphological, biochemical, physiological and molecular levels such as delayed flowering, reduced dry matter accumulation and decreased photosynthetic capacity as a result of stomatal closure, metabolic limitations and oxidative damage. Some of the physiological parameters that are affected during drought stress are root system, root/shoot ratio, stomatal frequency, leaf weight, leaf water potential, tissue water storage capacity, water permeability, leaf weight, thickness of cuticle, leaf chlorophyll content and finally, the yield. To withstand drought stress, plants need to be manipulated at the genetic level for improved metabolic processes like water absorption, stomatal conductance, transpiration, photosynthesis and finally seed development. Drought tolerance and adaptation in rice plants has been improved by engineering various genes related to transcription, signaling, accumulation of antioxidants and compatible solutes etc. In this review, we discuss the recent developments towards genetic engineering of transcription factors and protein kinases for enhancing drought stress tolerance in rice plants.
Sarvajeet Singh Gill, Ritu Gill (India), Naser A. Anjum (Portugal), Narendra Tuteja (India) Transgenic Approaches for Abiotic Stress Tolerance in Crop Plants (pp 73-83)
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ABSTRACT
Invited Review: Modern agriculture practice using genetically engineered crops is emerging as an effective tool to combat the negative impact of abiotic stresses on crop production. Abiotic stresses such as salt, drought, temperature, cold, flooding, heavy metals, etc. remain the greatest constraint to crop production. Estimations revealed that abiotic stresses alone responsible for crop failure and crop productivity loss between 50-70%. Global climate change further aggravating the frequency of abiotic stresses which is a serious challenge to feed the rapidly increasing world population. Plants respond to unfavorable environmental conditions in their habitat by developmental, physiological and biochemical ways to tolerate and/or sustain life. The main goal of modern agricultural research is to improve the potential of crop plants to survive under abiotic stresses for a long time. In this context, transgenic approaches are one of the potential ways for the genetic improvement of crop plants. Furthermore, functional genomics approaches revealed various mechanisms for crop improvement and abiotic stress tolerance. Genetic engineering of major crops such as rice, wheat, maize, soybean, pulses etc with genes from other sources is an extremely powerful tool for molecular plant breeding. Research has already come up with many transgenic crop plants with enhanced abiotic stress tolerance. The present article summarizes recent breakthroughs on the aforesaid aspects highlighting mainly transgenic plants overexpressing various genes for abiotic stress tolerance and improved crop productivity.
Nita Lakra, Kamlesh K. Nutan, Sneh L. Singla-Pareek, Ashwani Pareek (India) Modulating the Expression of Transcription Factors: An Attractive Strategy for Raising Abiotic Stress Tolerant Plants (pp 84-99)
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ABSTRACT
Invited Review: Plants, being sessile, are strongly influenced by abiotic stress such as high salt, drought, high temperature and freezing. These factors cause metabolic toxicity, membrane disorganization, closure of stomata, decreased photosynthetic activity, generation of reactive oxygen species (ROS) and altered nutrient acquisition. In order to meet the increasing demands for plant-based agricultural commodities, it would be imperative to enhance productivity of crop plants. It is well established that tolerance to abiotic stresses is mediated by a number of biochemical reactions and physiological processes, which essentially means that it is a ‘multigenic’ trait. A large number of stress related genes are expressed in an ‘orchestrated manner’ to bring about this stress response. For this ‘stress-responsive’ unique gene expression network to accrue, transcription factors play a very crucial role. Improvement in stress tolerance through engineering of transcription factors genes is emerging as an attractive strategy in recent years. The global expression analyses have also uncovered hundreds of genes encoding transcription factors that are differentially expressed under environmental stresses, thus implying that various transcriptional regulatory mechanisms are involved. Transcription factors often comprise families of related proteins that share a homologous DNA binding domain such as ERF, bZIP, MYC, MYB, NAC and WRKY binding transcription factors. There are several reports where increased tolerance has been achieved through the overexpression of selected transcription factor(s). The manipulation of a transcription factor can control a broad range of downstream events; therefore can combat abiotic stress efficiently. This review presents a brief description of important transgenic studies which have been attempted with a view to understand the role of various transcription factors towards abiotic stress tolerance in plants.
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