Search

Cells evolved some 4 billion years ago, and since then the integrity of the structural and functional continuity of cellular life has been maintained via highly conserved and ancient processes of cell reproduction and division. The plasma membrane as well as all the cytoplasmic structures are reproduced and inherited uninterruptedly by each of the two daughter cells resulting from every cell division. Although our understanding of the evolutionary emergence of the very first cells is obscured by the extremely long timeline since that revolutionary event, the generally accepted position is that the de novo formation of cells is not possible; all present cells are products of other prior cells. This essential biological principle was first discovered by Robert Remak and then effectively coined as Omnis Cellula e Cellula (every cell of the cell) by Rudolf Virchow: all currently living cells have direct structural and functional connections to the very first cells. Based on our previous theoretical analysis, all cells are endowed with individual sentient cognition that guides their individual agency, behaviour and evolution. There is a vital consequence of this new sentient and cognitive view of cells: when cells assemble as functional tissue ecologies and organs within multicellular organisms, including plants, animals and humans, these cellular aggregates display derivative versions of aggregate tissue‐ and organ‐specific sentience and consciousness. This innovative view of the evolution and physiology of all currently living organisms supports a singular principle: all organismal physiology is based on cellular physiology that extends from unicellular roots. [ABSTRACT FROM AUTHOR]

SUMMARY: The mechanistic basis by which boron (B) deprivation inhibits root growth via the mediation of root apical auxin transport and distribution remains elusive. This study showed that B deprivation repressed root growth of wild‐type Arabidopsis seedlings, which was related to higher auxin accumulation (observed with DII‐VENUS and DR5‐GFP lines) in B‐deprived roots. Boron deprivation elevated the auxin content in the root apex, coinciding with upregulation of the expression levels of auxin biosynthesis‐related genes (TAA1, YUC3, YUC9, and NIT1) in shoots, but not in root apices. Phenotyping experiments using auxin transport‐related mutants revealed that the PIN2/3/4 carriers are involved in root growth inhibition caused by B deprivation. B deprivation not only upregulated the transcriptional levels of PIN2/3/4, but also restrained the endocytosis of PIN2/3/4 carriers (observed with PIN‐Dendra2 lines), resulting in elevated protein levels of PIN2/3/4 in the plasma membrane. Overall, these results suggest that B deprivation not only enhances auxin biosynthesis in shoots by elevating the expression levels of auxin biosynthesis‐related genes but also promotes the polar auxin transport from shoots to roots by upregulating the gene expression levels of PIN2/3/4, as well as restraining the endocytosis of PIN2/3/4 carriers, ultimately resulting in auxin accumulation in root apices and root growth inhibition. Significance Statement: While boron (B) deprivation‐induced root growth inhibition is causally associated with auxin accumulation and transport, the underlying mechanisms remain unknown. This work showed that enhanced auxin biosynthesis resulting from upregulation of the expression levels of auxin biosynthesis‐related genes in shoots and increased protein levels of PIN2/3/4 carriers in the plasma membrane mediated by increased transcript levels of PIN2/3/4 genes in roots combined with restrained endocytosis of PIN2/3/4 carriers result in auxin overaccumulation in root apices and consequently root growth inhibition. [ABSTRACT FROM AUTHOR]

In this paper, we follow the evolutionary origins of cells as unicellular organisms and their evolution towards multicellularity, with a focus on plants and animals, both of which have two basic types of organismal self-identities: the immunological and the neuronal. Most cells of the animal immune system and its mesenchymal tissues are amoeba-like without flagella or cilia and form only loose cell–cell contacts. On the other hand, neuronal and epithelial cells are typically ciliated and assemble epithelial or neuronal synapses. In contrast, walled cells of higher plants lack flagella or cilia. However, lower plants up to the gymnosperm tree Ginkgo biloba have flagellated sperm cells. In our symbiotic concept of eukaryogenesis, the first ancient eukaryotic cells emerged from the merger of a large amoeba-like host cell with a small flagellated guest cell which later transformed into the eukaryotic nucleus. This duality at the origin of the eukaryotic cell matches with the duality of sexual gametes. It also corresponds to the immune system/neural dualities of organismal self-identities in both animals and plants. [ABSTRACT FROM AUTHOR]

We are sympathic with LeDoux's primary goal here ─ to get a solid scientific grip on what has been dubbed one of the most elusive, important questions in scientific discourse, to identify the underlying biomolecular processes that give rise to consciousness. However, we have issues with the way he goes about it and have tried to present them in a constructive manner. Our commentary is built around our theory of the origins of minds, dubbed the Cellular Basis of Consciousness (CBC), and the empirical research that supports it. The CBC is based on the proposition that life and sentience are co-terminous, that life without subjectivity, feeling, without valenced perception, without the capacity to learn and lay down memories would have been an evolutionary dead-end. It could not have survived in the hostile, chaotic world in flux that dominated our planet four billion years ago. The biological sciences operate on the principle that all species, extant and extinct, evolved from the first prokaryotes. The CBC theory is founded on the principle that all expressions of emotion, perception, and cognition did as well. [ABSTRACT FROM AUTHOR]

SUMMARY: The supply of boron (B) alleviates the toxic effects of aluminum (Al) on root growth; however, the mechanistic basis of this process remains elusive. This study filled this knowledge gap, demonstrating that boron modifies auxin distribution and transport in Al‐exposed Arabidopsis roots. In B‐deprived roots, treatment with Al induced an increase in auxin content in the root apical meristem zone (MZ) and transition zone (TZ), whereas in the elongation zone (EZ) the auxin content was decreased beyond the level required for adequate growth. These distribution patterns are explained by the fact that basipetal auxin transport from the TZ to the EZ was disrupted by Al‐inhibited PIN‐FORMED 2 (PIN2) endocytosis. Experiments involving the modulation of protein biosynthesis by cycloheximide (CHX) and transcriptional regulation by cordycepin (COR) demonstrated that the Al‐induced increase of PIN2 membrane proteins was dependent upon the inhibition of PIN2 endocytosis, rather than on the transcriptional regulation of the PIN2 gene. Experiments reporting on the profiling of Al3+ and PIN2 proteins revealed that the inhibition of endocytosis of PIN2 proteins was the result of Al‐induced limitation of the fluidity of the plasma membrane. The supply of B mediated the turnover of PIN2 endosomes conjugated with indole‐3‐acetic acid (IAA), and thus restored the Al‐induced inhibition of IAA transport through the TZ to the EZ. Overall, the reported results demonstrate that boron supply mediates PIN2 endosome‐based auxin transport to alleviate Al toxicity in plant roots. Significance Statement: Aluminum toxicity and boron deficiency are limiting factors for agricultural production in acid soils, which make up almost half of the world's arable land. Boron fertilization alleviates aluminum toxicity but the mechanism remains unclear. The study shows that boron supply releases aluminum‐induced root growth arrest by facilitating endosome‐based polar auxin transport via PIN2 polar localization in the upper half of the plasma membrane (shootward). We provide solid support for boron fertilizer in remediating aluminum toxicity in acid soils. [ABSTRACT FROM AUTHOR]