Alfonso Muñoz

Regulation of Translation Initiation under Abiotic Stress Conditions in Plants: Is It a Conserved or Not so Conserved Process among Eukaryotes?

For years, the study of gene expression regulation of plants in response to stress conditions has been focused mainly on the analysis of transcriptional changes. However, the knowledge on translational regulation is very scarce in these organisms, despite in plants, as in the rest of the eukaryotes, translational regulation has been proven to play a pivotal role in the response to different stresses. Regulation of protein synthesis under abiotic stress was thought to be a conserved process, since, in general, both the translation factors and the translation process are basically similar in eukaryotes. However, this conservation is not so clear in plants as the knowledge of the mechanisms that control translation is very poor. Indeed, some of the basic regulators of translation initiation, well characterised in other systems, are still to be identified in plants. In this paper we will focus on both the regulation of different initiation factors and the mechanisms that cellular mRNAs use to bypass the translational repression established under abiotic stresses. For this purpose, we will review the knowledge from different eukaryotes but paying special attention to the information that has been recently published in plants.

HOP3, a member of the HOP family in Arabidopsis, interacts with BiP and plays a major role in the ER stress response

HSP70-HSP90 organizing protein (HOP) is a well-studied family of cytosolic cochaperones. However, the possible role of HOP during the endoplasmic reticulum (ER) stress response and the identity of its interactors within the ER were not previously addressed in any eukaryote. We have demonstrated that Arabidopsis HOP3, whose function was not studied before, interacts in vivo with cytosolic HSP90 and HSP70, and, unexpectedly, with binding immunoglobulin protein (BiP), a HSP70 ER-resident protein. Although BiP lacks the domain described in other eukaryotes for HOP-HSP70 binding, it interacts with HOP3 through a non-canonical association to its nucleotide binding domain. Consistent with this interaction with BiP, HOP3 is partially localized at the ER. Moreover, HOP3 is induced both at transcript and protein levels by unfolded protein response (UPR) inducer agents by a mechanism dependent on inositol-requiring enzyme 1 (IRE1). Importantly, hop3 loss-of-function mutants show a reduction in pollen germination and a hypersensitive phenotype in the presence of ER stress inducer agents, a phenotype that is reverted by the addition of the chemical chaperone tauroursodeoxycholic acid (TUDCA). All these data demonstrate, for the first time in any eukaryote, a main role of HOP as an important regulator of the ER stress response, a process intimately linked in plants to important specific developmental programs and to environmental stress sensing and response.

Detection of distributed steganographic information in social networks

The peak of the new communications and social interactions through the Web makes less effective the use of classic automated tools of data acquisition. The massive appearance of authentication mechanisms, closed groups of users and, especially, mechanisms like captchas, makes really complex that automated tools can, in a simple manner, compile information and analyze it later. This paper reasons out how the characteristics of the present social networks can facilitate the presence of steganographic information. SDA steganalysis architecture is shown. SDA is composed of different tools to solve, as far as possible, the commented analysis problems. The paper emphasizes one tool, DCST, adapted to the steganalysis of Web content, mainly dynamic, typically present in the new social networks.

Hiding Short Secret Messages based on Linguistic Steganography and Manual Annotation

This article shows to what extent it is possible to develop a public simple mechanism for hiding information in natural language by means of the use of templates and manual annotation. The possibility of hiding a piece of information of a hundred of bits in a stegotext with a good linguistic quality is presented. This can be an interesting procedure for the exchange of cryptographic keys, urls, gps coordinates, mobilization messages, etc. The article shows examples for Spanish language, but the same idea it is possible in other languages.

PRNG based on new HCI devices entropy sources: Wii remote study case

This paper analyzes the possibilities of cutting edge HCI (HumanComputer Interaction) devices for random number generation. Their increasing presence in electronic devices is a fact, so they may be taken into account for PRNG. As an example, the Wii control device (Wii Remote) is analyzed. Among other characteristics, it includes accelerometers and an IR camera, which can be a valid source of entropic information. As these characteristics are appearing in other devices (for example, mobile phones), the aim of this paper is to study the reliability of these sensors as sources of non-predictive information, which could be useful in many areas. Standard algorithm methodologies are used to corroborate the analysis. Its usage as seed of a PRNG could be analyzed by other kind of tests, NIST SP 800-22 among others.

HOP family plays a major role in long-term acquired thermotolerance in Arabidopsis: AtHOP family is involved in thermotolerance

HSP70-HSP90 organizing protein (HOP) is a family of cytosolic cochaperones whose molecular role in thermotolerance is quite unknown in eukaryotes and unexplored in plants. In this article, we describe that the three members of the AtHOP family display a different induction pattern under heat, being HOP3 highly regulated during the challenge and the attenuation period. Despite HOP3 is the most heat-regulated member, the analysis of the hop1 hop2 hop3 triple mutant demonstrates that the three HOP proteins act redundantly to promote long-term acquired thermotolerance in Arabidopsis. HOPs interact strongly with HSP90 and part of the bulk of HOPs shuttles from the cytoplasm to the nuclei and to cytoplasmic foci during the challenge. RNAseq analyses demonstrate that, although the expression of the Hsf targets is not generally affected, the transcriptional response to heat is drastically altered during the acclimation period in the hop1 hop2 hop3 triple mutant. This mutant also displays an unusual high accumulation of insoluble and ubiquitinated proteins under heat, which highlights the additional role of HOP in protein quality control. These data reveal that HOP family is involved in different aspects of the response to heat, affecting the plant capacity to acclimate to high temperatures for long periods.

HOP3 a new regulator of the ER stress response in Arabidopsis with possible implications in plant development and response to biotic and abiotic stresses

ABSTRACT HOPs (heat shock protein 70 (HSP70)-heat shock protein 90 (HSP90) organizing proteins) are a highly conserved family of cytosolic cochaperones. In a recent study we showed that HOP3, a member of the HOP family in Arabidopsis, plays an essential role during endoplasmic reticulum (ER) stress in plants. Interestingly, we also demonstrated that AtHOP3 interacts with binding immunoglobulin protein (BiP), a major ER-resident chaperone. All these data suggest that HOP3 could assist BiP in protein folding in the ER. These findings open the exciting possibility that HOP3, through its role in the alleviation of ER stress, could play an important function during different developmental processes and in response to different biotic and abiotic stresses.

Evolutionary Aspects of Translation Regulation During Abiotic Stress and Development in Plants

In the last decade, different studies have highlighted the importance translational control in plant development and in response to environmental cues. Although most translation factors are conserved in plants, our current knowledge about translation regulation in this kingdom is still scarce. This chapter will outline the mechanisms controlling the selective translation of mRNAs under different abiotic stresses and developmental conditions in several eukaryotic model systems, discussing whether similar or specific mechanisms exist in plants.

A formal model for the creation and evaluation of steganographic solutions based in lexical-semantic substitutions: a case applied to Spanish

This paper develops a formal model that allows research, development and evaluation from a functional point of view and attending to security needs, of the different parts in the process of creation of a linguistic steganographic system based on the lexical-semantic substitution of words by their synonyms. The advantages and drawbacks of this type of steganographic technique and the procedure to evaluate its usefulness in a given language are discussed. As a case study, the application of this model is carried out in the Spanish language based on the development of the tool Lexical Substitution in Spanish. This tool allows the testing of the substitution of words with their synonyms in Spanish. A hiding capacity of at least 0.1864bits/word, resulting in 68.33% of the stegotexts created being invisible to the attacks analysed. This hiding capacity is useful enough to send Internet addresses, GPS coordinates, brief mobility messages, signatures on text, control messages, and so forth. All these uses are in fact very practical within the area of telecommunication networks. From the point of view of corporate network security, stegotexts make possible, for example, the control of a botnet without any knowledge on the part of the network administrators. Copyright

Coimmunoprecipitation of Interacting Proteins in Plants

Protein-protein interactions discovered by yeast two-hybrid systems must be confirmed in vivo in a homologous system. In the case of plants, one of the easiest and fastest methods to validate protein interactions in vivo is the transient expression of the proteins in Nicotiana benthamiana leaves followed by coimmunoprecipitation. This method consists of the following steps: growth of the appropriate Agrobacterium tumefaciens cultures, preparation of the infiltration mixtures, infiltration into N. benthamiana leaves, protein extraction and immunoprecipitation. The utilization of epitope tags to immunoprecipitate and detect the proteins of interest is very useful in this procedure. In this chapter we describe a standard protocol to coimmunoprecipitate proteins expressed in N. benthamiana leaves.