From Biosemiotics to Code Biology

Major evolutionary transitions before cells: a journey from molecules to organisms

Basing on logical assumptions and necessary steps of complexification along biological evolution, we propose here an evolutionary path from molecules to cells presenting four ages and three major transitions. At the first age, the basic biomolecules were formed and become abundant. The first transition happened with the event of a chemical symbiosis between nucleic acids and peptides worlds, which marked the emergence of both life and the process of organic encoding. FUCA, the first living process, was composed of self-replicating RNAs linked to amino acids and capable to catalyze their binding. The second transition, from the age of FUCA to the age of progenotes, involved the duplication and recombination of proto-genomes, leading to specialization in protein production and the exploration of protein to metabolite interactions in the prebiotic soup. Enzymes and metabolic pathways were incorporated into biology from protobiotic reactions that occurred without chemical catalysts, step by step. Then, the fourth age brought origin of organisms and lineages, occurring when specific proteins capable to stackle together facilitated the formation of peptidic capsids. LUCA was constituted as a progenote capable to operate the basic metabolic functions of a cell, but still unable to interact with lipid molecules. We present evidence that the evolution of lipid interaction pathways occurred at least twice, with the development of bacterial-like and archaeal-like membranes. Also, data in literature suggest at least two paths for the emergence of DNA biosynthesis, allowing the stabilization of early life strategies in viruses, archaeas and bacterias. Two billion years later, the eukaryotes arouse, and after 1,5 billion years of evolution, they finally learn how to evolve multicellularity via tissue specialization.

How ambiguity codes specify molecular descriptors and information flow in Code Biology

The article presents IUPAC ambiguity codes for incomplete nucleic acid specification, and their use in Code Biology. It is shown how to use this nomenclature in order to extract accurate information on different properties of the biological systems. We investigated the use of ambiguity codes, as mathematical and logical operators and truth table elements, for the encoding of amino acids by means of the Standard Genetic Code. It is explained how to use ambiguity codes and truth functions in order to obtain accurate information on different properties of the biological systems. Nucleotide ambiguity codes could be applied to: 1. encoding descriptive information of nucleotides, amino acids and proteins (e.g., of polarity, relative solvent accessibility, atom depth, etc.), and 2. system modelling ranging from standard bioinformatics tools to classic evolutionary models (i.e. from Miyazawa-Jernigan statistical potential to Kimura three-substitution-type model, respectively). It is shown that the algorithms based on IUPAC ambiguity codes, Boolean functions and truth table, Probabilistic Square of Opposition/Semiotic Square and Klein 4-groups-could be used for the bioinformatics analyses and Relational data modelling in natural science. Underlying mathematical, logical and semiotic concepts of interest are presented and addressed.

New algorithm for the analysis of nucleotide and amino acid evolutionary relationships based on Klein four-group

Phylogenetics is the study of ancestral relationships among biological species. Such sequence analyses are often represented as phylogenetic trees. The branching pattern of each tree and its topology reflect the evolutionary relatedness between analyzed sequences. We present a Klein four-group algorithm (K4A) for the evolutionary analysis of nucleotide and amino acid sequences. Klein four-group set of operators consists of: identity e (U), and three elements-a = transition (C), b = transversion (G) and c = transition-transversion or complementarity (A). We generated Klein four-group based distance matrices of: 1. Cayley table (CK4), 2. Table rows (K4R), 3. Table columns (K4C), and 4. Euclidean 2D distance (K4E). The performance of the matrices was tested on a dataset of RecA proteins in bacteria, eukaryotes (Rad51 homolog) and archaea (RadA homolog). RecA and its functional homologs are found in all species, and are essential for the repair and maintenance of DNA. Consequently, they represent a good model for the study of evolutionary relationship of protein and nucleotide sequences. The ancestral relationship between the sequences was correctly classified by all K4A matrices concerning general topology. All distance matrices exhibited small variations among species, and overall results of tree classification were in agreement with the general patterns obtained by standard BLOSUM and PAM substitution matrices. During the evolution of a code there is a phase of optimization of system rules, the ambiguity of a code is eliminated, and the system starts producing specific components. Klein four-group algorithm is consistent with the concept of ambiguity reduction. It also enables the use of different genetic code table variants optimized for particular transitions in evolution based on biological specificity.

Decoding viruses: An alternative perspective on their history, origins and role in nature

This article provides an alternative perspective on viruses, exploring their origins, ecology, and evolution. Viruses are recognized as the most prevalent biological entities on Earth, permeating nearly all environments and forming the virosphere-a significant biological layer. They play a crucial role in regulating bacterial populations within ecosystems and holobionts, influencing microbial communities and nutrient recycling. Viruses are also key drivers of molecular evolution, actively participating in the maintenance and regulation of ecosystems and cellular organisms. Many eukaryotic genomes contain genomic elements with viral origins, which contribute to organismal equilibrium and fitness. Viruses are involved in the generation of species-specific orphan genes, facilitating adaptation and the development of unique traits in biological lineages. They have been implicated in the formation of vital structures like the eukaryotic nucleus and the mammalian placenta. The presence of virus-specific genes absent in cellular organisms suggests that viruses may pre-date cellular life. Like progenotes, viruses are ribonucleoprotein entities with simpler capsid architectures compared to proteolipidic membranes. This article presents a comprehensive scenario describing major transitions in prebiotic evolution and proposes that viruses emerged prior to the Last Universal Common Ancestor (LUCA) during the progenote era. However, it is important to note that viruses do not form a monophyletic clade, and many viral taxonomic groups originated more recently as reductions of cellular structures. Thus, viral architecture should be seen as an ancient and evolutionarily stable strategy adopted by biological systems. The goal of this article is to reshape perceptions of viruses, highlighting their multifaceted significance in the complex tapestry of life and fostering a deeper understanding of their origins, ecological impact, and evolutionary dynamics.

Origin of life: Drawing the big picture

Trying to provide a broad overview about the origin of life in Earth, the most significant transitions of life before cells are listed and discussed. The current approach emphasizes the symbiotic relationships that emerged with life. We propose a rational, stepwise scenario for the origin of life that starts with the origin of the first biomolecules and steps forward until the origins of the first cells. Along this path, we aim to provide a brief, though comprehensive theoretical model that will consider the following steps: (i) how nucleotides and other biomolecules could be made prebiotically in specific prebiotic refuges; (ii) how the first molecules of RNAs were formed; (iii) how the proto-peptidyl transferase center was built by the concatenation of proto-tRNAs; (iv) how the ribosome and the genetic code could be structured; (v) how progenotes could live and reproduce as "naked" ribonucleoprotein molecules; (vi) how peptides started to bind molecules in the prebiotic soup allowing biochemical pathways to evolve from those bindings; (vii) how genomes got bigger by the symbiotic relationship of progenotes and lateral transference of genetic material; (viii) how the progenote LUCA has been formed by assembling most biochemical routes; (ix) how the first virion capsids probably emerged and evolved; (x) how phospholipid membranes emerged probably twice by the evolution of lipid-binding proteins; (xi) how DNA synthesis have been formed in parallel in Bacteria and Archaea; and, finally, (xii) how DNA-based cells of Bacteria and Archaeabacteria have been constituted. The picture provided is conjectural and present epistemological gaps. Future research will help to advance into the elucidation of gaps and confirmation/refutation of current statements.

Complexification of eukaryote phenotype: Adaptive immuno-cognitive systems as unique Gödelian block chain distributed ledger

The digitization of inheritable information in the genome has been called the 'algorithmic take-over of biology'. The McClintock discovery that viral software based transposable elements that conduct cut-paste (transposon) and copy-paste (retrotransposon) operations are needed for genomic evolvability underscores the truism that only software can change software and also that viral hacking by internal and external bio-malware is the Achilles heel of genomic digital systems. There was a paradigm shift in genomic information processing with the Adaptive Immune System (AIS) 500 mya followed by the Mirror Neuron System (MNS), latterly mostly in primate brains, which reaches its apogee in human social cognition. The AIS and MNS involve distinctive Gödelian features of self-reference (Self-Ref) and offline virtual self-representation (Self-Rep) for complex self-other interaction with prodigious open-ended capacity for anticipative malware detection and novelty production within a unique blockchain distributed ledger (BCDL). The role of self-referential information processing, often considered to be central to the sentient self with origins in the immune system 'Thymic self', is shown to be part of the Gödel logic behind a generator-selector framework at a molecular level, which exerts stringent selection criteria to maintain genomic BCDL. The latter manifests digital and decentralized record keeping where no internal or external bio-malware can compromise the immutability of the life's building blocks and no novel blocks can be added that is not consistent with extant blocks. This is demonstrated with regard to somatic hypermutation with novel anti-body production in the face of external non-self antigen attacks.

Organic Codes: A Unifying Concept for Life

Although the knowledge about biological systems has advanced exponentially in recent decades, it is surprising to realize that the very definition of Life keeps presenting theoretical challenges. Even if several lines of reasoning seek to identify the essence of life phenomenon, most of these thoughts contain fundamental problem in their basic conceptual structure. Most concepts fail to identify either necessary or sufficient features to define life. Here, we analyzed the main conceptual frameworks regarding theoretical aspects that have been supporting the most accepted concepts of life, such as (i) the physical, (ii) the cellular and (iii) the molecular approaches. Based on an ontological analysis, we propose that Life should not be positioned under the ontological category of Matter. Yet, life should be better understood under the top-level ontology of "Process". Exercising an epistemological approach, we propose that the essential characteristic that pervades each and every living being is the presence of organic codes. Therefore, we explore theories in biosemiotics and code biology in order to propose a clear concept of life as a macrocode composed by multiple inter-related coding layers. This way, as life is a sort of metaphysical process of encoding, the living beings became the molecular materialization of that process. From the proposed concept, we show that the evolutionary process is a fundamental characteristic for life's maintenance but it is not necessary to define life, as many organisms are clearly alive but they do not participate in the evolutionary process (such as infertile hybrids). The current proposition opens a fertile field of debate in astrobiology, epistemology, biosemiotics, code biology and robotics.

Archetypes and code biology

As a clinical psychologist, I observe stereotyped formulas of behavior in action every day in the consulting room, despite differences in age, race, or culture; they present themselves as codified rules or typical modes of behavior in archetypical situations. Such circumstances coincide with what C.G. Jung defended: the existence of archetypes stored in an inherited/phylogenetic repository, which he called the collective unconscious - somewhat similar to the notion of an ethogram, as shown by ethology. Psychologists can use a perspective to facilitate understanding the phenomenon: the code biology perspective (Barbieri 2014). This approach can help us recognize how these phenomenological events have an ontological reality based not only on the existence of organic information but also on the existence of organic meaning. We are not a tabula rasa (Wilson 2000): despite the explosive diversification of the brain and the emergence of conscience and intentionality, we observe the conservation of basic instincts and emotions (Ekman 2004; Damasio 2010) not only in humans but in all mammals and other living beings; we refer to the neural activity on which the discrimination behavior is based, i.e., the neural codes. The conservation of these fundamental set-of-rules or conventions suggests that one or more neural codes have been highly conserved and serves as an interpretive basis for what happens to the living being who owns them (Barbieri 2003). Thus, archetypes' phenomenological reality can be understood not as something metaphorical but as an ontological (phylogenetic) fact (Goodwyn 2019). Furthermore, epigenetic regulation theories present the possibility that the biomolecular process incorporates elements of the context where it takes place; something fundamental to understand our concept - the archetype presents itself as the mnesic remnant of the behavioral history of individuals who preceded us on the evolutionary scale. In short: brains are optimized for processing ethologically relevant sensory signals (Clemens et al., 2015). From the perspective of the corporeal mind (Searle 2002), in this paper, we will show the parallels between code biology and the concept of the archetype, as Jung defended it and as it appears in clinical practice.

Metacode: One code to rule them all

The code of codes or metacode is a microcosm where biological layers, as well as their codes, interact together allowing the continuity of information flow in organisms by increasing biological entities' complexity. Through this novel organic code, biological systems scale towards niches with higher informatic freedom building structures that increase the entropy in the universe. Code biology has developed a novel informational framework where biological entities strive themselves through the information flow carried out through organic codes consisting of two molecular or functional landscapes intertwined through arbitrary linkages via an adaptor whose nature is autonomous from molecular determinism. Here we will integrate genomic and epigenomic codes according to the evidence released in ENCODE (phase 3), psychENCODE and GTEx project, outlining the principles of the metacode, to address the continuous nature of biological systems and their inter-layered information flow. This novel complex metacode maps from very constrained sets of elements (i.e., regulation sites modulating gene expression) to new ones with greater freedom of decoding (i.e., a continuous cell phenotypic space). This leads to a new domain in code biology where biological systems are informatic attractors that navigate an energy metaspace through a complexity-noise balance, stalling in emergent niches where organic codes take meaning.

Karyotype coding: The creation and maintenance of system information for complexity and biodiversity

The mechanism of biological information flow is of vital importance. However, traditional research surrounding the genetic code that follows the central dogma to a phenotype faces challengers, including missing heritability and two-phased evolution. Here, we propose the karyotype code, which by organizing genes along chromosomes at once preserves species genome information and provides a platform for other genetic and nongenetic information to develop and accumulate. This specific genome-level code, which exists in all living systems, is compared to the genetic code and other organic codes in the context of information management, leading to the concept of hierarchical biological codes and an 'extended' definition of adaptor where the adaptors of a code can be not only molecular structures but also, more commonly, biological processes. Notably, different levels of a biosystem have their own mechanisms of information management, and gene-coded parts inheritance preserves "parts information" while karyotype-coded system inheritance preserves the "system information" which organizes parts information. The karyotype code prompts many questions regarding the flow of biological information, including the distinction between information creation, maintenance, modification, and usage, along with differences between living and non-living systems. How do biological systems exist, reproduce, and self-evolve for increased complexity and diversity? Inheritance is mediated by organic codes which function as informational tools to organize chemical reactions, create new information, and preserve frozen accidents, transforming historical miracles into biological routines.

Life and living beings under the perspective of organic macrocodes

A powerful and concise concept of life is crucial for studies aiming to understand the characteristics that emerged from an inorganic world. Among biologists, the most accepted argument define life under a top-down strategy by looking into the shared characteristics observed in all cellular organisms. This is often made highlighting (i) autonomy and (ii) evolutionary capacity as fundamental characteristics observed in all cellular organisms. Along the present work, we assume the framework of code biology considering that biology started with the emergence of the first organic code by self-organization. We reinforces that the conceptual structure of life should be reallocated from the ontology class of Matter to its sister class of Process. Along the emergence and early evolution of biological systems, biological codes changed from open systems of "naked" molecules (at the progenote era), to close, encapsulated systems (at the organismic era). Living beings appeared at the very moment when nucleic acids with coding properties became encapsulated. This led to the origin of viruses and, then, to the origin of cells. In this context, we propose that the single character that makes a clear distinction between the abiotic and the biotic world is the capacity to process organic codes. Thus, life appears with the self-assembly of a genetic code and evolves by the emergence of other overlapping codes. Once life has been clearly conceptualized, we go further to conceptualize organisms, parents, lineages, and species in terms of code biology.

On the origin of mental representations

The symbol grounding problem raises its head in the fields of the philosophy of AI, philosophy of psychology and philosophy of cognitive sciences. The solution to the symbol grounding problem must account for the genesis of mental representations in the world. It has to offer a strategy for grounding mental representations in the objective domain. Orthodox representationalist theories do not provide a satisfactory reply to the symbol grounding problem. On the other hand, there are embodied-enactivist approaches that dissolve the problem but only at the cost of representations and internal phenomenal states. The code model of biosemiotics provides a biologically viable (i.e., mechanistic) venue for developing a new solution to the problem. For the same reason, it could reconcile representationalism to the embodied approach.

A new theory of development: the generation of complexity in ontogenesis

Today there is a very wide consensus on the idea that embryonic development is the result of a genetic programme and of epigenetic processes. Many models have been proposed in this theoretical framework to account for the various aspects of development, and virtually all of them have one thing in common: they do not acknowledge the presence of organic codes (codes between organic molecules) in ontogenesis. Here it is argued instead that embryonic development is a convergent increase in complexity that necessarily requires organic codes and organic memories, and a few examples of such codes are described. This is the code theory of development, a theory that was originally inspired by an algorithm that is capable of reconstructing structures from incomplete information, an algorithm that here is briefly summarized because it makes it intuitively appealing how a convergent increase in complexity can be achieved. The main thesis of the new theory is that the presence of organic codes in ontogenesis is not only a theoretical necessity but, first and foremost, an idea that can be tested and that has already been found to be in agreement with the evidence.

DNA as information

This article reviews contributions to this theme issue covering the topic 'DNA as information' in relation to the structure of DNA, the measure of its information content, the role and meaning of information in biology and the origin of genetic coding as a transition from uninformed to meaningful computational processes in physical systems.