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1. Isoelectronic perturbations to f - d -electron hybridization and the enhancement of hidden order in URu ₂ Si ₂

   https://doi.org/10.1073/pnas.2026591118  

   Wolowiec, Christian T. ; Kanchanavatee, Noravee ; Huang, Kevin ; Ran, Sheng ; Breindel, Alexander J. ; Pouse, Naveen ; Sasmal, Kalyan ; Baumbach, Ryan E. ; Chappell, Greta ; Riseborough, Peter S. ; et al ( May 2021 , Proceedings of the National Academy of Sciences)

   Electrical resistivity measurements were performed on single crystals of URu_2–xOs_xSi₂up tox= 0.28 under hydrostatic pressure up toP= 2 GPa. As the Os concentration,x, is increased, 1) the lattice expands, creating an effective negative chemical pressureP_ch(x); 2) the hidden-order (HO) phase is enhanced and the system is driven toward a large-moment antiferromagnetic (LMAFM) phase; and 3) less external pressureP_cis required to induce the HO→LMAFM phase transition. We compare the behavior of theT(x,P) phase boundary reported here for the URu_2-xOs_xSi₂system with previous reports of enhanced HO in URu₂Si₂upon tuning withPor similarly in URu_2–xFe_xSi₂upon tuning with positiveP_ch(x). It is noteworthy that pressure, Femore »substitution, and Os substitution are the only known perturbations that enhance the HO phase and induce the first-order transition to the LMAFM phase in URu₂Si₂. We present a scenario in which the application of pressure or the isoelectronic substitution of Fe and Os ions for Ru results in an increase in the hybridization of the U-5f-electron and transition metald-electron states which leads to electronic instability in the paramagnetic phase and the concurrent formation of HO (and LMAFM) in URu₂Si₂. Calculations in the tight-binding approximation are included to determine the strength of hybridization between the U-5f-electron states and thed-electron states of Ru and its isoelectronic Fe and Os substituents in URu₂Si₂.

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2. Variation in the flowering time orthologs BrFLC and BrSOC1 in a natural population of Brassica rapa

   https://doi.org/10.7717/peerj.1339  

   Franks, Steven J. ; Perez-Sweeney, Beatriz ; Strahl, Maya ; Nowogrodzki, Anna ; Weber, Jennifer J. ; Lalchan, Rebecca ; Jordan, Kevin P. ; Litt, Amy ( November 2015 , PeerJ)

   Understanding the genetic basis of natural phenotypic variation is of great importance, particularly since selection can act on this variation to cause evolution. We examined expression and allelic variation in candidate flowering time loci inBrassica rapaplants derived from a natural population and showing a broad range in the timing of first flowering. The loci of interest were orthologs of the Arabidopsis genesFLCandSOC1(BrFLCandBrSOC1, respectively), which in Arabidopsis play a central role in the flowering time regulatory network, withFLCrepressing andSOC1promoting flowering. InB. rapa, there are four copies ofFLCand three ofSOC1. Plants were grown in controlled conditions in the lab. Comparisons were mademore »between plants that flowered the earliest and latest, with the difference in average flowering time between these groups ∼30 days. As expected, we found that total expression ofBrSOC1paralogs was significantly greater in early than in late flowering plants. Paralog-specific primers showed that expression was greater in early flowering plants in theBrSOC1paralogsBr004928, Br00393andBr009324, although the difference was not significant inBr009324. Thus expression of at least 2 of the 3BrSOC1orthologs is consistent with their predicted role in flowering time in this natural population. Sequences of the promoter regions of theBrSOC1orthologs were variable, but there was no association between allelic variation at these loci and flowering time variation. For theBrFLCorthologs, expression varied over time, but did not differ between the early and late flowering plants. The coding regions, promoter regions and introns of these genes were generally invariant. Thus theBrFLCorthologs do not appear to influence flowering time in this population. Overall, the results suggest that even for a trait like flowering time that is controlled by a very well described genetic regulatory network, understanding the underlying genetic basis of natural variation in such a quantitative trait is challenging.

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3. AGLF provides C-function in floral organ identity through transcriptional regulation of AGAMOUS in Medicago truncatula

   https://doi.org/10.1073/pnas.1820468116  

   Zhao, Yang ; Liu, Rong ; Xu, Yiteng ; Wang, Minmin ; Zhang, Jing ; Bai, Mingyi ; Han, Chao ; Xiang, Fengning ; Wang, Zeng-Yu ; Mysore, Kirankumar S. ; et al ( February 2019 , Proceedings of the National Academy of Sciences)

   Floral development is one of the model systems for investigating the mechanisms underlying organogenesis in plants. Floral organ identity is controlled by the well-known ABC model, which has been generalized to many flowering plants. Here, we report a previously uncharacterized MYB-like gene,AGAMOUS-LIKE FLOWER(AGLF), involved in flower development in the model legumeMedicago truncatula. Loss-of-function ofAGLFresults in flowers with stamens and carpel transformed into extra whorls of petals and sepals. Compared with the loss-of-function mutant of the class C geneAGAMOUS(MtAG) inM. truncatula, the defects in floral organ identity are similar betweenaglfandmtag, but the floral indeterminacy is enhanced in theaglfmutant. Knockout ofAGLFin themore »mutants of the class A geneMtAP1or the class B geneMtPIleads to an addition of a loss-of-C-function phenotype, reflecting a conventional relationship ofAGLFwith the canonical A and B genes. Furthermore, we demonstrate thatAGLFactivatesMtAGin transcriptional levels in control of floral organ identity. These data shed light on the conserved and diverged molecular mechanisms that control flower development and morphology among plant species.

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4. Three new karst-dwelling Cnemaspis Strauch, 1887 (Squamata; Gekkoniade) from Peninsular Thailand and the phylogenetic placement of C. punctatonuchalis and C. vandeventeri

   https://doi.org/10.7717/peerj.2884  

   Wood Jr, Perry Lee ; Grismer, L. Lee ; Aowphol, Anchalee ; Aguilar, César A. ; Cota, Micheal ; Grismer, Marta S. ; Murdoch, Matthew L. ; Sites Jr, Jack W. ( January 2017 , PeerJ)

   Three new species of Rock GeckosCnemaspis lineogularissp. nov.,C. phangngaensissp. nov., andC. thachanaensissp. nov. of thechanthaburiensisandsiamensisgroups are described from the Thai portion of the Thai-Malay Peninsula. These new species are distinguished from all other species in their two respective groups based on a unique combination of morphological characteristics, which is further supported by mitochondrial DNA (mtDNA) from the NADH dehydrogenase subunit 2 gene (ND2).Cnemaspis lineogularissp. nov. is differentiated from all other species in thechanthaburiensisgroup by having a smaller maximum SVL 38 mm, 13 paravertebral tubercles, enlarged femoral scales, no caudal bands, and a 19.5–23.0% pairwise sequence divergence (ND2).Cnemaspis phangngaensissp. nov. is differentiated from allmore »other species in the siamensis group by having the unique combination of 10 infralabial scales, four continuous pore-bearing precloacal scales, paravertebral tubercles linearly arranged, lacking tubercles on the lower flanks, having ventrolateral caudal tubercles anteriorly present, caudal tubercles restricted to a single paraveterbral row on each side, a single median row of keeled subcaudals, and a 8.8–25.2% pairwise sequence divergence (ND2).Cnemaspis thachanaensissp. nov. is distinguished from all other species in the siamensis group by having 10 or 11 supralabial scales 9–11 infralabial scales, paravertebral tubercles linearly arranged, ventrolateral caudal tubercles anteriorly, caudal tubercles restricted to a single paravertebral row on each side, a single median row of keeled subcaudal scales, lacking a single enlarged subcaudal scale row, lacking postcloaclal tubercles in males, the presence of an enlarged submetatarsal scale at the base if the 1st toe, and a 13.4–28.8% pairwise sequence divergence (ND2). The new phylogenetic analyses placeC. punctatonuchalisandC. vandeventeriin the siamensis group withC. punctatonuchalisas the sister species toC. huaseesomandC. vandeventerias the sister species toC. siamensis, corroborating previous hypotheses based on morphology. The discovery of three new karst-dwelling endemics brings the total number of nominal ThaiCnemaspisspecies to 15 and underscores the need for continued field research in poorly known areas of the Thai-Malay Peninsula, especially those that are threatened and often overlooked as biodiversity hot spots.

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5. What doesn’t kill them makes them stronger: an association between elongation factor 1- α overdominance in the sea star Pisaster ochraceus and “sea star wasting disease”

   https://doi.org/10.7717/peerj.1876  

   Wares, John P. ; Schiebelhut, Lauren M. ( March 2016 , PeerJ)

   In recent years, a massive mortality event has killed millions of sea stars, of many different species, along the Pacific coast of North America. This disease event, known as ‘sea star wasting disease’ (SSWD), is linked to viral infection. In one affected sea star (Pisaster ochraceus), previous work had identified that the elongation factor 1-αlocus (EF1A) harbored an intronic insertion allele that is lethal when homozygous yet appears to be maintained at moderate frequency in populations through increased fitness for heterozygotes. The environmental conditions supporting this increased fitness are unknown, but overdominance is often associated with disease. Here, we evaluatemore »populations ofP. ochraceusto identify the relationship between SSWD and EF1A genotype. Our data suggest that there may be significantly decreased occurrence of SSWD in individuals that are heterozygous at this locus. These results suggest further studies are warranted to understand the functional relationship between diversity at EF1A and survival inP. ochraceus.

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