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1. Evolution of Plant Hormone Response Pathways

   https://doi.org/10.1146/annurev-arplant-050718-100309  

   Blázquez, Miguel A.; Nelson, David C.; Weijers, Dolf (April 2020, Annual Review of Plant Biology)

   null (Ed.)

   This review focuses on the evolution of plant hormone signaling pathways. Like the chemical nature of the hormones themselves, the signaling pathways are diverse. Therefore, we focus on a group of hormones whose primary perception mechanism involves an Skp1/Cullin/F-box-type ubiquitin ligase: auxin, jasmonic acid, gibberellic acid, and strigolactone. We begin with a comparison of the core signaling pathways of these four hormones, which have been established through studies conducted in model organisms in the Angiosperms. With the advent of next-generation sequencing and advanced tools for genetic manipulation, the door to understanding the origins of hormone signaling mechanisms in plants beyond these few model systems has opened. For example, in-depth phylogenetic analyses of hormone signaling components are now being complemented by genetic studies in early diverging land plants. Here we discuss recent investigations of how basal land plants make and sense hormones. Finally, we propose connections between the emergence of hormone signaling complexity and major developmental transitions in plant evolution. 

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2. Peroxisomal Stress Response and Inter-Organelle Communication in Cellular Homeostasis and Aging

   https://doi.org/10.3390/antiox11020192  

   Kim, J; Bai, H (January 2022, Antioxidants)

   Santos, AL (Ed.)

   Peroxisomes are key regulators of cellular and metabolic homeostasis. These organelles play important roles in redox metabolism, the oxidation of very-long-chain fatty acids (VLCFAs), and the biosynthesis of ether phospholipids. Given the essential role of peroxisomes in cellular homeostasis, peroxisomal dysfunction has been linked to various pathological conditions, tissue functional decline, and aging. In the past few decades, a variety of cellular signaling and metabolic changes have been reported to be associated with defective peroxisomes, suggesting that many cellular processes and functions depend on peroxisomes. Peroxisomes communicate with other subcellular organelles, such as the nucleus, mitochondria, endoplasmic reticulum (ER), and lysosomes. These inter-organelle communications are highly linked to the key mechanisms by which cells surveil defective peroxisomes and mount adaptive responses to protect them from damages. In this review, we highlight the major cellular changes that accompany peroxisomal dysfunction and peroxisomal inter-organelle communication through membrane contact sites, metabolic signaling, and retrograde signaling. We also discuss the age-related decline of peroxisomal protein import and its role in animal aging and age-related diseases. Unlike other organelle stress response pathways, such as the unfolded protein response (UPR) in the ER and mitochondria, the cellular signaling pathways that mediate stress responses to malfunctioning peroxisomes have not been systematically studied and investigated. Here, we coin these signaling pathways as “peroxisomal stress response pathways”. Understanding peroxisomal stress response pathways and how peroxisomes communicate with other organelles are important and emerging areas of peroxisome research. 

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3. Diverse roles for axon guidance pathways in adult tissue architecture and function

   https://doi.org/10.1002/ntls.20220021  

   Laws, Kaitlin M.; Bashaw, Greg J. (October 2022, Natural Sciences)

   Abstract Classical axon guidance ligands and their neuronal receptors were first identified due to their fundamental roles in regulating connectivity in the developing nervous system. Since their initial discovery, it has become clear that these signaling molecules play important roles in the development of a broad array of tissue and organ systems across phylogeny. In addition to these diverse developmental roles, there is a growing appreciation that guidance signaling pathways have important functions in adult organisms, including the regulation of tissue integrity and homeostasis. These roles in adult organisms include both tissue‐intrinsic activities of guidance molecules, as well as systemic effects on tissue maintenance and function mediated by the nervous and vascular systems. While many of these adult functions depend on mechanisms that mirror developmental activities, such as regulating adhesion and cell motility, there are also examples of adult roles that may reflect signaling activities that are distinct from known developmental mechanisms, including the contributions of guidance signaling pathways to lineage commitment in the intestinal epithelium and bone remodeling in vertebrates. In this review, we highlight studies of guidance receptors and their ligands in adult tissues outside of the nervous system, focusing on in vivo experimental contexts. Together, these studies lay the groundwork for future investigation into the conserved and tissue‐specific mechanisms of guidance receptor signaling in adult tissues. Key PointsAxon guidance ligand and receptor expression often persist into adulthood in neuronal and non‐neuronal tissues alike.Recent work in genetic model organisms highlights the diverse roles of guidance factors in adult tissues.Guidance factors are required intrinsically in a variety of adult tissues but can also regulate tissue function indirectly via functions in the nervous and vascular systems.Studies outside of the nervous system are likely to enhance our understanding of these diverse siganling molecules and could suggest novel signaling modalities in the nervous system. 

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4. Role of heterotrimeric G-proteins in improving abiotic stress tolerance of crop plants

   Parinita Majumdar, P; Torres Rodríguez, MD; Pandey, S (January 2022, Journal of plant growth regulation)

   Sopory, SK (Ed.)

   As sessile organisms, plants are constantly exposed to a variety of environmental stresses that have detrimental effects on their growth and development, leading to major crop yield losses worldwide. To cope with adverse conditions plants have developed several adaptive mechanisms. A thorough understanding these mechanisms is critical to generate plants for the future. The heterotrimeric G-protein complex, composed of Gα, Gβ, and Gγ subunits, participates in regulation of multiple cellular signaling pathways and have multifaceted roles in regulating stress responses of plants. The complex has two functional entities, the GTP-bound Gα subunit and the Gβγ dimer, both of which by interacting with additional proteins can activate various signaling networks. The involvement of G-proteins has been shown in plants’ response to drought, salinity, extreme temperatures, heavy metal, ozone, and UV-B radiation. Due to their versatility and the number of processes modulated by them, G-proteins have emerged as key targets for generating stress tolerant crops. In this review, we provide an overview of the current knowledge of the roles of G proteins in abiotic stress tolerance, with examples from model plant Arabidopsis thaliana, where these processes are most widely studied and from additional agriculturally relevant crops, where their potential is realized for human usage. 

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5. Chapter Nine - The biosynthesis and roles of N-acylethanolamines in plants

   Arias-Gaguancela, O.; Chapman, K.D. (January 2022, Advances in botanical research)

   Rebeille, F.; Marechal, E. (Ed.)

   N-acylethanolamines (NAEs) are a group of lipid signaling molecules derived from the phospholipid precursor N-acylphosphatidylethanolamine (NAPE). NAEs can be processed by a wide range of metabolic processes including hydrolysis by fatty acid amide hydrolase (FAAH), peroxidation by lipoxygenases (LOX), and conjugation by glycosyl- and malonyl-transferases. The diversity of NAE metabolites points to participation in multiple downstream pathways for regulation and function. NAEs with acyl chains of 18C are typically the most predominant types in vascular plants. Whereas in nonvascular plants and some algae, the arachidonic acid-containing NAE, anandamide (a functional “endocannabinoid” in animal systems), was recently reported. A signaling role for anandamide and other NAEs is well established in vertebrates, while NAEs and their oxylipin metabolites are recently becoming appreciated for lipid mediator roles in vascular plants. Here, the NAE metabolism and function in plants are overviewed, with particular emphasis on processes described in vascular plants where most attention has been focused. 

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