Branch patterns in trees and art
image:
Leonardo da Vinci’s sketch of a tree illustrates the principle that combined thickness is preserved at different stages of ramification.
view moreCredit: Institut de France Manuscript M, p. 78v.
The math that describes the branching pattern of trees in nature also holds for trees depicted in art—and may even underlie our ability to recognize artworks as depictions of trees.
Trees are loosely fractal, branching forms that repeat the same patterns at smaller and smaller scales from trunk to branch tip. Jingyi Gao and Mitchell Newberry examine scaling of branch thickness in depictions of trees and derive mathematical rules for proportions among branch diameters and for the approximate number of branches of different diameters. The authors begin with Leonardo da Vinci’s observation that trees limbs preserve their thickness as they branch. The parameter α, known as the radius scaling exponent in self-similar branching, determines the relationships between the diameters of the various branches. If the thickness of a branch is always the same as the summed thickness of the two smaller branches, as da Vinci asserts, then the parameter α would be 2. The authors surveyed trees in art, selected to cover a broad geographical range and also for their subjective beauty, and found values from 1.5 to 2.8, which correspond to the range of natural trees. Even abstract works of art that don’t visually show branch junctions or treelike colors, such as Piet Mondrian’s cubist Gray Tree, can be visually identified as trees if a realistic value for α is used. By contrast, Mondrian’s later painting, Blooming Apple Tree, which sets aside scaling in branch diameter, is not recognizable as a tree. According to the authors, art and science provide complementary lenses on the natural and human worlds.
Combined cross-sectional area (πr2 ) is preserved across branching. The tree on the right uses such transects to count the number of branches n that have radius approximately r to derive a fractal scaling relationship.
Three trees generated by the same random algorithm differ only in the value of α used to compute the branch diameters. The algorithm stops adding branches when the radius reaches roughly 1/10th that of the trunk, creating exponentially more branches for higher values of α.
Credit
Jingyi Gao and Mitchell Newberry
Gray Tree, by Piet Mondrian, 1911.
Blossoming apple tree, by Piet Mondriaan, 1912.
Journal
PNAS Nexus
Article Title
Scaling in branch thickness and the fractal aesthetics of trees
Article Publication Date
11-Feb-2025
Grapevine anthocyanins: how drought stress triggers colorful adaptations
image:
Model describing how drought mediates ABA-induced anthocyanin biosynthesis via the VvAREB2-miR156b-VvSBP8/13 pathway in grape berries.
view moreCredit: Horticulture Research
New research has uncovered a surprising silver lining to drought conditions—enhancing the color and quality of grapes by increasing anthocyanin levels through a finely tuned molecular pathway. Scientists have identified how drought stress activates the ABA signaling pathway, triggering the microRNA miR156b. This microRNA, in turn, suppresses specific inhibitors (VvSBP8 and VvSBP13) of anthocyanin production, effectively removing roadblocks to pigment accumulation. With these barriers lifted, the MBW complex—a key regulator of anthocyanin biosynthesis—forms more efficiently, leading to richer, deeper hues in grape berries. This discovery not only advances our understanding of grapevine resilience but also offers practical strategies for improving grape quality in drought-prone regions, presenting significant opportunities for the global wine industry.
Anthocyanins, the pigments responsible for the vibrant red and purple hues of grape berries and wines, are highly sensitive to environmental conditions, particularly water availability. While moderate drought has long been observed to enhance anthocyanin levels, the molecular mechanisms underlying this phenomenon have remained elusive. Given the critical role of water management in viticulture, unlocking the regulatory pathways that govern anthocyanin accumulation under drought stress could provide game-changing insights for grape growers and winemakers worldwide.
A new study (DOI: 10.1093/hr/uhad293), published on January 2, 2024, in Horticulture Research, by researchers from Nanjing Agricultural University and Northwest A&F University, has now bridged this knowledge gap. The study reveals how drought stress stimulates anthocyanin biosynthesis in grape berries via the ABA signaling pathway and the microRNA miR156b. These findings offer crucial insights into how grapevines respond to water scarcity and provide a foundation for enhancing grape quality through precise genetic and environmental interventions.
Delving into the molecular intricacies, the researchers identified miR156b as a master regulator of anthocyanin biosynthesis under drought conditions. Their study showed that drought stress elevates the transcription factor VvAREB2, which directly binds to the promoter of the miR156b gene, switching on its expression. This activation is pivotal, as miR156b selectively targets and suppresses VvSBP8 and VvSBP13, two transcription factors known to inhibit the MYB-bHLH-WD40 (MBW) complex, a crucial driver of anthocyanin biosynthesis. By neutralizing these inhibitors, miR156b allows the MBW complex to function unimpeded, resulting in a significant boost in anthocyanin production. The study further demonstrated that manipulating miR156b levels in grape calli and berries directly impacts anthocyanin accumulation—with overexpression of miR156b leading to intensified pigmentation, while suppression reduced anthocyanin levels. This intricate regulatory network, involving ABA signaling, miR156b, and the MBW complex, provides a comprehensive model of how drought stress enhances anthocyanin production in grapes. Furthermore, it suggests miR156b as a potential genetic target for breeding drought-resilient, high-quality grape cultivars.
Dr. Tengfei Xu, one of the lead researchers, underscores the transformative nature of these findings: "Our study establishes a direct molecular link between drought stress and anthocyanin biosynthesis, mediated by the ABA signaling pathway and miR156b. This discovery opens new possibilities for improving grape quality and resilience in water-limited environments, offering a sustainable approach to viticulture in the face of climate change."
Beyond scientific discovery, this research carries profound implications for viticulture and grape breeding. Understanding the molecular mechanisms that drive anthocyanin accumulation under drought conditions can help growers refine irrigation strategies to maximize grape quality while conserving water. Additionally, the insights gained could accelerate the development of drought-tolerant grape varieties, ensuring more sustainable wine production in an era of increasing climate challenges. By harnessing the power of genetics and precision agriculture, this study offers a blueprint for a more resilient and vibrant future for the global wine industry.
###
References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhad293
Funding information
This work was supported by the National Natural Science Foundation of China (grants 32371924, 32260727, and 31801811), the Key Research and Development Program of Shaanxi Province (grant 2023-GHZD-17), the Key Research and Development Programme of Xinjiang Province (grant 2022B02034-3), and the China Agriculture Research System (grant CARS-29-zp-6).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2022. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.
Journal
Horticulture Research
Subject of Research
Not applicable
Article Title
miR156b-targeted VvSBP8/13 functions downstream of the abscisic acid signal to regulate anthocyanins biosynthesis in grapevine fruit under drought
Study finds that birds-of-paradise are
biofluorescent
Research suggests that “hidden” phenomenon provides enhanced signaling for hierarchy and courtship displays
image:
Biofluorescence is seen on an emperor bird-of-paradise (Paradisaea guilielmi) in the American Museum of Natural History's collection.
view moreCredit: © Rene Martin
New research by scientists at the American Museum of Natural History and the University of Nebraska-Lincoln reports, for the first time, the widespread occurrence of biofluorescence in birds-of-paradise. The study, based on Museum specimens collected since the 1800s, finds biofluorescence in 37 of the 45 known birds-of-paradise species and suggests that this special “glow” is important among males for hierarchy and mating displays. The research is published today in the journal Royal Society Open Science.
“The unique mating rituals and displays of birds-of-paradise have fascinated scientists and spurred a myriad of studies focused on trait evolution and sexual selection,” said the study’s lead author Rene Martin, an assistant professor at the University of Nebraska-Lincoln who conducted this work when she was a postdoctoral researcher at the Museum. “It seems fitting that these flashy birds are likely signaling to each other in additional, flashy ways.”
Biofluorescence is a phenomenon that occurs when an organism absorbs light, transforms it, and emits it as a different color. In recent years, Museum Curator John Sparks, an ichthyologist, and his colleagues have identified previously unknown biofluorescence in hundreds of species across the tree of life, with a particular focus on fishes. Using a specialized photography setup with ultraviolet and blue lights and emission filters, the researchers have captured biofluorescence in animals ranging from sharks to turtles to corals. About a decade ago, Sparks worked closely with Museum ornithologists to search for biofluorescence in the Museum’s vast collection among a subset of birds that are known for their courtship displays.
“Despite there being over 10,000 described avian species, with numerous studies that have documented their bright plumage, elaborate mating displays, and excellent vision, surprisingly very few have investigated the presence of biofluorescence,” Sparks said.
Bowerbirds and fairy wrens failed to glow, but among birds-of-paradise, Sparks found bright green-yellow fluorescence. Sparks’ initial work was continued recently by Martin and Emily Carr, a Ph.D. student in the Museum’s Richard Gilder Graduate School. Together, the team took a closer look at biofluorescence in birds-of-paradise, which live across eastern Australia, Indonesia, and New Guinea, finding that the birds also fluoresce when exposed to UV light, not just blue light. This phenomenon is especially prominent in males, focused on their bright plumage and skin in areas that are highlighted during displays: the inner mouth and bill, feet, and feathers on the head, neck, and belly. In females, biofluorescence is usually restricted to plumage on the chest and belly.
“These birds live near the equator, where there is an abundance of bright solar light year-round, and they live in forests where the complexity of light is significantly affected by differences in the canopy and where biofluorescent signals may be enhanced,” Carr said.
Studies based on closely related species found that the pigments in the birds’ eyes align with the fluorescence peaks that the researchers measured. Based on this, the authors infer that birds-of-paradise can see these biofluorescent patterns, which enhance contrast against dark plumage and possibly play an important role in courtship and hierarchy.
Funding for this work was provided by the American Museum of Natural History’s Department of Ichthyology, the Richard Gilder Graduate School, and the Gerstner Scholarship.
Study DOI: https://doi.org/10.1098/rsos.241905
Biofluorescence is seen on the plumage of an emperor bird-of-paradise (Paradisaea guilielmi) in the American Museum of Natural History's collection.
Credit
@ Rene Martin
No comments:
Post a Comment