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SMAX1-LIKE (SMXL) proteins in plants are cellular signaling hubs, many of which are posttranslationally regulated by karrikins from smoke, the plant hormones strigolactones (SLs), and/or cues such as light and nutrients. SMXL proteins control diverse aspects of growth, development, and environmental adaptation in plants through transcriptional corepression and interactions with transcriptional regulator proteins. In flowering plants, the SMXL family comprises four phylogenetic clades with different roles. Functions of the aSMAX1 clade include control of germination and seedling development, while the SMXL78 clade controls shoot architecture. We investigated how SMXL roles are specified inArabidopsis thaliana.Through promoter-swapping experiments, we found thatSMXL7can partially replicateSMAX1function, butSMAX1cannot replaceSMXL7. This implies that the distinct roles of these genes are primarily due to differences in protein sequences rather than expression patterns. To determine which part of SMXL proteins specifies downstream control, we tested a series of protein chimeras and domain deletions of SMAX1 and SMXL7. We found an N-terminal region that is necessary and sufficient to specify control of germination, seedling growth, or axillary branching. We screened 158 transcription factors (TFs) for interactions with SMAX1 and SMXL7 in yeast two-hybrid assays. The N-terminal domain was necessary and/or sufficient for most of the 33 potential protein–protein interactions that were identified for SMAX1. This finding unlocks different ways to engineer plant growth control through cross-wiring SMXL regulatory “input” and developmental “output” domains from different clades and lays a foundation for understanding how functional differences evolved in the SMXL family. 

Thermally induced ripples are intrinsic features of nanometer-thick films, atomically thin materials, and cell membranes, significantly affecting their elastic properties. Despite decades of theoretical studies on the mechanics of suspended thermalized sheets, controversy still exists over the impact of these ripples, with conflicting predictions about whether elasticity is scale-dependent or scale-independent. Experimental progress has been hindered so far by the inability to have a platform capable of fully isolating and characterizing the effects of ripples. This knowledge gap limits the fundamental understanding of thin materials and their practical applications. Here, we show that thermal-like static ripples shape thin films into a class of metamaterials with scale-dependent, customizable elasticity. Utilizing a scalable semiconductor manufacturing process, we engineered nanometer-thick films with precisely controlled frozen random ripples, resembling snapshots of thermally fluctuating membranes. Resonant frequency measurements of rippled cantilevers reveal that random ripples effectively renormalize and enhance the average bending rigidity and sample-to-sample variations in a scale-dependent manner, consistent with recent theoretical estimations. The predictive power of the theoretical model, combined with the scalability of the fabrication process, was further exploited to create kirigami architectures with tailored bending rigidity and mechanical metamaterials with delayed buckling instability. 

Strigolactones (SLs) are methylbutenolide molecules derived from β-carotene through an intermediate carlactonoic acid (CLA). Canonical SLs act as signals to microbes and plants, whereas noncanonical SLs are primarily plant hormones. The cytochrome P450 CYP722C catalyzes a critical step, converting CLA to canonical SLs in most angiosperms. Using synthetic biology, we investigated the function ofCYP722A, an evolutionary predecessor ofCYP722C. CYP722A converts CLA into 16-hydroxy-CLA (16-OH-CLA), a noncanonical SL detected exclusively in the shoots of various flowering plants. 16-OH-CLA application restores control of shoot branching to SL-deficient mutants inArabidopsis thalianaand is perceived by the SL signaling pathway. We hypothesize that biosynthesis of 16-OH-CLA by CYP722A was a metabolic stepping stone in the evolution of canonical SLs that mediate rhizospheric signaling in many flowering plants. 

ABSTRACT SMAX1-LIKE (SMXL) proteins are transcriptional co-repressors that regulate many aspects of plant growth and development. Proteins from the SMAX1- and SMXL78-clades of this family are targeted for degradation after karrikin or strigolactone perception, triggering downstream responses. We investigated how SMXL proteins control development.SMXL7can partially replicateSMAX1function in seeds and seedlings, butSMAX1cannot replaceSMXL7in shoot branching control. Therefore, the distinct roles of these genes arise from differences in protein activity more than expression. Analysis of chimeras and domain deletions of SMAX1 and SMXL7 proteins revealed that an N-terminal domain is necessary and sufficient to specify developmental functions. We screened 158 transcription factors for interactions with SMAX1. The N-terminal domain is necessary and/or sufficient for the majority of candidate interactions. These discoveries enable cross-wiring of karrikin and strigolactone control of plant development and lay a foundation for understanding how SMXL proteins evolved functional differences. 

The bagrada bug,Bagrada hilaris(Burmeister), is an emerging agricultural pest in the Americas, threatening agricultural production in the southwestern United States, Mexico and Chile, as well as in the Old World (including Africa, South Asia and, more recently, Mediterranean areas of Europe). Substantive transcriptomic sequence resources for this damaging species would be beneficial towards understanding its capacity for developing insecticide resistance, identifying viruses that may be present throughout its population and identifying genes differentially expressed across life stages that could be exploited for biomolecular pesticide formulations. This study establishesB.hilaristranscriptomic resources for eggs, 2^ndand 4^thlarval instars, as well as male and female adults. Three gene families involved in xenobiotic detoxification—glutathione S-transferases, carboxylesterases and cytochrome P450 monooxygenases—were phylogenetically characterized. These data were also qualitatively compared with previously published results for two closely related pentatomid species—the brown marmorated stink bug,Halyomorpha halys(Stål), and the harlequin bug,Murgantia histrionica(Hahn)—to elucidate shared enzymatic components of terpene-based sex pheromone biosynthetic pathways. Lastly, the sequence data were screened for potential RNAi- and virus-related content and for genes implicated in insect growth and development. 

Hormone-activated proteolysis is a recurring theme of plant hormone signaling mechanisms. In strigolactone signaling, the enzyme-receptor DWARF14 (D14) and an F-box protein, MORE AXILLARY GROWTH2 (MAX2), mark SUPPRESSOR OF MAX2 1- LIKE (SMXL) family proteins SMXL6, SMXL7, and SMXL8 for rapid degradation. Removal of these transcriptional corepressors initiates downstream growth responses. The homologous proteins SMXL3, SMXL4, and SMXL5, however, are resistant to MAX2- mediated degradation. We discovered that the smxl4 smxl5 mutant has enhanced responses to strigolactone. SMXL5 attenuates strigolactone signaling by interfering with AtD14-SMXL7 interactions. SMXL5 interacts with AtD14 and SMXL7, providing two possible ways to inhibit SMXL7 degradation. SMXL5 function is partially dependent on an EAR motif that typically mediates interactions with the TOPLESS family of transcriptional corepressors. However, we find that loss of the EAR motif reduces SMXL5-SMXL7 interactions and the attenuation of strigolactone signaling by SMXL5. We hypothesize that integration of SMXL5 into heteromeric SMXL complexes reduces the susceptibility of SMXL6/7/8 proteins to strigolactone-activated degradation, and that the EAR motif promotes the formation or stability of these complexes. This mechanism may provide a way to spatially or temporally fine-tune strigolactone signaling through the regulation of SMXL5 expression or translation. 

Conical surfaces pose an interesting challenge to crystal growth: A crystal growing on a cone can wrap around and meet itself at different radii. We use a disk-packing algorithm to investigate how this closure constraint can geometrically frustrate the growth of single crystals on cones with small opening angles. By varying the crystal seed orientation and cone angle, we find that—except at special commensurate cone angles—crystals typically form a seam that runs along the axial direction of the cone, while near the tip, a disordered particle packing forms. We show that the onset of disorder results from a finite-size effect that depends strongly on the circumference and not on the seed orientation or cone angle. This finite-size effect occurs also on cylinders, and we present evidence that on both cylinders and cones, the defect density increases exponentially as circumference decreases. We introduce a simple model for particle attachment at the seam that explains the dependence on the circumference. Our findings suggest that the growth of single crystals can become frustrated even very far from the tip when the cone has a small opening angle. These results may provide insights into the observed geometry of conical crystals in biological and materials applications. 

We investigate the ground-state configurations of two-dimensional liquid crystals with p-fold rotational symmetry (p-atics) on fixed curved surfaces. We focus on the intrinsic geometry and show that isothermal coordinates are particularly convenient as they explicitly encode a geometric contribution to the elastic potential. In the special case of a cone with half-angle β, the apex develops an effective topological charge of −χ, where 2πχ = 2π(1 − sin β) is the deficit angle of the cone, and a topological defect of charge σ behaves as if it had an effective topological charge Qeff = (σ − σ2/2) when interacting with the apex. The effective charge of the apex leads to defect absorption and emission at the cone apex as the deficit angle of the cone is varied. For total topological defect charge 1, e.g., imposed by tangential boundary conditions at the edge, we find that for a disk the ground-state configuration consists of p defects each of charge +1/p lying equally spaced on a concentric ring of radius d = ( p−1 3p−1 ) 1 2p R, where R is the radius of the disk. In the case of a cone with tangential boundary conditions at the base, we find three types of ground-state configurations as a function of cone angle: (i) for sharp cones, all of the +1/p defects are absorbed by the apex; (ii) at intermediate cone angles, some of the +1/p defects are absorbed by the apex and the rest lie equally spaced along a concentric ring on the flank; and (iii) for nearly flat cones, all of the +1/p defects lie equally spaced along a concentric ring on the flank. Here the defect positions and the absorption transitions depend intricately on p and the deficit angle, which we analytically compute. We check these results with numerical simulations for a set of commensurate cone angles and find excellent agreement.