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Strigolactones (SLs) are a unique and novel class of phytohormones that regulate numerous processes of growth and development in plants. Besides their endogenous functions as hormones, SLs are exuded by plant roots to stimulate critical interactions with symbiotic fungi but can also be exploited by parasitic plants to trigger their seed germination. In the past decade, since their discovery as phytohormones, rapid progress has been made in understanding the SL biosynthesis and signaling pathway. Of particular interest are the diversification of natural SLs and their exact mode of perception, selectivity, and hydrolysis by their dedicated receptors in plants. Here we provide an overview of the emerging field of SL perception with a focus on the diversity of canonical, non-canonical, and synthetic SL probes. Moreover, this review offers useful structural insights into SL perception, the precise molecular adaptations that define receptor-ligand specificities, and the mechanisms of SL hydrolysis and its attenuation by downstream signaling components.

Despite the fundamental importance of plants to our very survival, student interest in plant biology is in decline as technology draws us further away from nature. Here we introduce "Plant Tracer" (http://www.planttracer.com), a Matlab-based program, which can quantify time-lapse videos of plant movement. We demonstrate that Plant Tracer can be used to distinguish altered movement qualities in the inflorescence (flowering) stem in the Arabidopsis "pgm-1" (phosphoglucomutase) mutant when compared to wildtype, providing a genetic platform for students to evaluate how plants sense and respond to gravity and circumnutation (the back-and-forth swaying of plant organs). We show that both gravitropism and circumnutation is diminished in the "pgm-1" mutant when compared to wildtype. In this way, "Plant Tracer" is a promising instructional tool for biology labs to quantify the genetics of plant movement using smartphones.

KAI2 proteins are plant α/β hydrolase receptors which perceive smoke-derived butenolide signals and endogenous, yet unidentified KAI2-ligands (KLs). The number of functional KAI2 receptors varies among species and KAI2 gene duplication and sub-functionalization likely plays an adaptative role by altering specificity towards different KLs. Legumes represent one of the largest families of flowering plants and contain many agronomic crops. Prior to their diversification, KAI2 underwent duplication resulting in KAI2A and KAI2B. Here we demonstrate that Pisum sativum KAI2A and KAI2B are active receptors and enzymes with divergent ligand stereoselectivity. KAI2B has a higher affinity for and hydrolyses a broader range of substrates including strigolactone-like stereoisomers. We determine the crystal structures of PsKAI2B in apo and butenolide-bound states. The biochemical, structural, and mass spectra analyses of KAI2s reveal a transient intermediate on the catalytic serine and a stable adduct on the catalytic histidine, confirming its role as a bona fide enzyme. Our work uncovers the stereoselectivity of ligand perception and catalysis by diverged KAI2 receptors and proposes adaptive sensitivity to KAR/KL and strigolactones by KAI2B.

Cryptochromes (CRYs) are evolutionarily conserved photoreceptors that mediate various light-induced responses in bacteria, plants, and animals. Plant cryptochromes govern a variety of critical growth and developmental processes including seed germination, flowering time and entrainment of the circadian clock. CRY's photocycle involves reduction of their flavin adenine dinucleotide (FAD)-bound chromophore, which is completely oxidized in the dark and semi to fully reduced in the light signaling-active state. Despite the progress in characterizing cryptochromes, important aspects of their photochemistry, regulation, and light-induced structural changes remain to be addressed. In this study, we determine the crystal structure of the photosensory domain of Arabidopsis CRY2 in a tetrameric active state. Systematic structure-based analyses of photo-activated and inactive plant CRYs elucidate distinct structural elements and critical residues that dynamically partake in photo-induced oligomerization. Our study offers an updated model of CRYs photoactivation mechanism as well as the mode of its regulation by interacting proteins.

Plants are constantly exposed to volatile organic compounds (VOCs) that are released during plant-plant communication, within-plant self-signaling, and plant-microbe interactions. Therefore, understanding VOC perception and downstream signaling is vital for unraveling the mechanisms behind information exchange in plants, which remain largely unexplored. Using the hormone-like function of volatile terpenoids in reproductive organ development as a system with a visual marker for communication, we demonstrate that a petunia karrikin-insensitive receptor, PhKAI2ia, stereospecifically perceives the (−)-germacrene D signal, triggering a KAI2-mediated signaling cascade and affecting plant fitness. This study uncovers the role(s) of the intermediate clade of KAI2 receptors, illuminates the involvement of a KAI2ia-dependent signaling pathway in volatile communication, and provides new insights into plant olfaction and the long-standing question about the nature of potential endogenous KAI2 ligand(s). [ABSTRACT FROM AUTHOR]

The article discusses a study by Jacob B. Landis et al., published in Science (2024), exploring how natural selection influences genetic diversity in barley over long-term adaptation experiments. It is reported that the study sequenced genomes to track the evolutionary trajectory. It found that initially diverse genetic variation in CCII rapidly homogenized, favoring alleles adapted to local conditions like the dry summer season.

Despite the fundamental importance of plants to our very survival, student interest in plant biology is in decline as technology draws us further away from nature. Here we introduce Plant Tracer (http://www.planttracer.com), a Matlab-based program, which can quantify time-lapse videos of plant movement. We demonstrate that Plant Tracer can be used to distinguish altered movement qualities in the inflorescence (flowering) stem in the Arabidopsis pgm-1 (phosphoglucomutase) mutant when compared to wildtype, providing a genetic platform for students to evaluate how plants sense and respond to gravity and circumnutation (the back-and-forth swaying of plant organs). We show that both gravitropism and circumnutation is diminished in the pgm-1 mutant when compared to wildtype. In this way, Plant Tracer is a promising instructional tool for biology labs to quantify the genetics of plant movement using smartphones. [ABSTRACT FROM AUTHOR]

Proteolysis, including post-translational proteolytic processing as well as protein degradation and amino acid recycling, is an essential component of the growth and development of living organisms. In this article, experts in plant proteolysis pose and discuss compelling open questions in their areas of research. Topics covered include the role of proteolysis in the cell cycle, DNA damage response, mitochondrial function, the generation of N-terminal signals (degrons) that mark many proteins for degradation (N-terminal acetylation, the Arg/N-degron pathway, and the chloroplast N-degron pathway), developmental and metabolic signaling (photomorphogenesis, abscisic acid and strigolactone signaling, sugar metabolism, and post-harvest regulation), plant responses to environmental signals (endoplasmic-reticulum associated degradation, chloroplast-associated degradation, drought tolerance, the growth-defense tradeoff)), and the functional diversification of peptidases. We hope these thought-provoking discussions help to stimulate further research., (© The Author(s) 2024. Published by Oxford University Press on behalf of American Society of Plant Biologists.)