(Press-News.org)
Auxin is the first plant hormone—or "phytohormone"—ever identified, with its discovery dating to the late 19th and early 20th centuries. With its discovery, scientists began to understand how small, self-produced organic molecules could influence physiological processes in plants such as growth, cell division, flowering, fruit ripening, and stress responses.
The auxin family of phytohormones promotes cell elongation and root development and is involved in directional growth, such as growing toward light. It works by moving directionally within plant tissues to establish concentration gradients, thereby regulating key developmental processes. This directional transport is orchestrated by three protein families: the PIN, ABCB, and AUX1/LAX families.
While scientists previously understood how PIN proteins export auxin out of cells, the import mechanism by AUX1/LAX proteins remained unclear.
Now, however, research teams led by Prof. SUN Linfeng, Prof. LIU Xin, and Prof. TAN Shutang from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences have unveiled the structures of Arabidopsis AUXIN RESISTANT 1 protein (AUX1) and clarified the molecular mechanism by which this protein transports auxin into the cell via the proton concentration gradient. The study was published in Cell on May 15.
To elucidate the transport mechanism controlled by Arabidopsis AUX1, the researchers employed biochemical assays, structural biology, and computational simulations. Through microscale thermophoresis and isothermal titration calorimetry, they demonstrated that AUX1-mediated auxin binding and transport were proton-dependent and could be inhibited by the known small molecules 1-naphthoxyacetic acid (1-NOA) and 3-chloro-4-hydroxyphenylacetic acid (CHPAA).
Furthermore, using cryo-electron microscopy, the researchers determined high-resolution structures of AUX1 in three distinct states: apo (substrate-free), auxin-bound (IAA), and inhibitor-bound (CHPAA). These structures revealed, for the first time, the overall architecture of the AUX1/LAX family of proteins—which features an inward-facing conformation, with 11 transmembrane helices adopting a classical LeuT fold.
In the auxin-bound structure, several key residues involved in IAA recognition were identified—most notably His249 (H249), which underwent a marked side-chain reorientation upon substrate binding. The functional relevance of these residues was confirmed through site-directed mutagenesis, biochemical assays, and plant physiological experiments.
To further investigate the role of H249 in substrate recognition and proton coupling, the researchers, collaborating with Prof. ZHU Lizhe's team from the Chinese University of Hong Kong (Shenzhen), performed molecular dynamics simulations. Comparative analysis of the IAA- and CHPAA-bound structures showed that, while both ligands occupied a similar binding pocket, they exhibited distinct interaction patterns. These differences provided mechanistic insights into how CHPAA inhibits AUX1-mediated auxin transport.
This study, which reveals for the first time the molecular basis of auxin import mediated by the AUX1/LAX protein family in plants, represents an important breakthrough in understanding plant growth and development.
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The finding adds to our understanding of how subtle genetic changes give rise to new traits, the researchers said.
Lots of mammals come in shades of orange — think tigers, ...
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CellScapes introduces a groundbreaking approach that will combine cutting-edge imaging and powerful ...
At its heart, this research uncovers the hidden geometric principles behind the unique shape of rose petals. While scientists extensively studied shape morphing in natural sheets such as leaves and petals, the team at Hebrew University discovered a new player: MCP incompatibility—a geometric principle that causes the petal’s signature cusps. It turns out that as the petal grows, stress builds at the edges, shaping the curves we recognize and love. The discovery not only uncovered the geometric origin of the shape of rose petals, but also introduces a new paradigm for ...
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South African study identifies two new breast cancer genes in black women
Genetic factors contribute to some 30% of breast cancer cases in SA, necessitating investment in genomic research in African contexts.
A seminal genetic study published in Nature Communication has discovered two genetic variants linked to breast cancer in black South African women, deepening knowledge about the genetic basis for this disease in African populations.
The genome-wide association study (GWAS) of breast cancer is the first to have been done in African women living on the continent.
A GWAS is a powerful ...
A new, incision-free technique developed at UVA Health to treat debilitating brain lesions called cerebral cavernous malformations, or cavernomas, has shown great promise in early testing, halting the growth of the lesions almost entirely.
The new approach could represent a paradigm shift in how the malformations, commonly called CCMs, are treated, the researchers say. The technique uses tiny, gas-filled “microbubbles” propelled by focused sound waves to open the brain’s protective barrier and stunt the growth of the malformations.
“This is a clear example ...
Prevention and treatment campaigns are not adequately targeting the particular needs of the 50+ years age group.
Indeed, between 2000 and 2016, the number of adults aged 50 years and older living with HIV in sub-Saharan Africa doubled. At present, their HIV prevalence is exceeding that of younger adults.
By 2040, one-quarter of people living with HIV in Africa will be aged 50 years and older; tailored awareness and treatment campaigns are pressing.
Dr Luicer Olubayo, a researcher at the Sydney Brenner ...
There is always a need for a refrigerant with a large ΔH at operating temperature. On the other hand, refrigeration equipment generally available typically functions near/below RT. Thus, for ferroelectric refrigeration to be practical, a large ΔH at a transition near/below RT is essential. Representative PST ceramics demonstrate substantial promise for EC refrigeration near RT, attracting considerable interest. The highly ordered PST ceramic always has excellent EC properties, while it is difficult to achieve. Previous researchers often employed a heat treatment process combining high-temperature quenching and long-term annealing to obtain highly ...
New research uncovers the strongest solar event ever detected — rewriting our understanding of space weather and radiocarbon dating.
An international team of scientists has discovered an extreme spike in radiocarbon corresponding to the year 12350 BC during the dusk of the last Ice Age. However, the strength of the event could not be assessed earlier because of the lack of an appropriate model. Presently, it has been identified as the most powerful solar particle storm known to date – a colossal ...
The study, in which the Biodiversity and Evolution Research Group of the UPV/EHU’s Faculty of Science and Technology participated, was carried out within the framework of the international DarkDivNet network and focused on nearly 5,500 locations in 119 regions across the world. In each location studied, the research teams analysed all the plant species present in different habitats to identify dark diversity. This innovative methodology for studying biodiversity made it possible to estimate the potential plant diversity in each study site and compare it with the plants actually present.
The results reveal a hitherto unknown effect of human activities on biodiversity. ...
