237 research outputs found
Group-invariant soliton equations and bi-Hamiltonian geometric curve flows in Riemannian symmetric spaces
Universal bi-Hamiltonian hierarchies of group-invariant (multicomponent)
soliton equations are derived from non-stretching geometric curve flows
\map(t,x) in Riemannian symmetric spaces , including compact
semisimple Lie groups for , . The derivation
of these soliton hierarchies utilizes a moving parallel frame and connection
1-form along the curve flows, related to the Klein geometry of the Lie group
where is the local frame structure group. The soliton
equations arise in explicit form from the induced flow on the frame components
of the principal normal vector N=\covder{x}\mapder{x} along each curve, and
display invariance under the equivalence subgroup in that preserves the
unit tangent vector T=\mapder{x} in the framing at any point on a curve.
Their bi-Hamiltonian integrability structure is shown to be geometrically
encoded in the Cartan structure equations for torsion and curvature of the
parallel frame and its connection 1-form in the tangent space T_\map M of the
curve flow. The hierarchies include group-invariant versions of sine-Gordon
(SG) and modified Korteweg-de Vries (mKdV) soliton equations that are found to
be universally given by curve flows describing non-stretching wave maps and
mKdV analogs of non-stretching Schrodinger maps on . These results provide
a geometric interpretation and explicit bi-Hamiltonian formulation for many
known multicomponent soliton equations. Moreover, all examples of
group-invariant (multicomponent) soliton equations given by the present
geometric framework can be constructed in an explicit fashion based on Cartan's
classification of symmetric spaces.Comment: Published version, with a clarification to Theorem 4.5 and a
correction to the Hamiltonian flow in Proposition 5.1
Hamiltonian evolutions of twisted gons in \RP^n
In this paper we describe a well-chosen discrete moving frame and their
associated invariants along projective polygons in \RP^n, and we use them to
write explicit general expressions for invariant evolutions of projective
-gons. We then use a reduction process inspired by a discrete
Drinfeld-Sokolov reduction to obtain a natural Hamiltonian structure on the
space of projective invariants, and we establish a close relationship between
the projective -gon evolutions and the Hamiltonian evolutions on the
invariants of the flow. We prove that {any} Hamiltonian evolution is induced on
invariants by an evolution of -gons - what we call a projective realization
- and we give the direct connection. Finally, in the planar case we provide
completely integrable evolutions (the Boussinesq lattice related to the lattice
-algebra), their projective realizations and their Hamiltonian pencil. We
generalize both structures to -dimensions and we prove that they are
Poisson. We define explicitly the -dimensional generalization of the planar
evolution (the discretization of the -algebra) and prove that it is
completely integrable, providing also its projective realization
Symplectically-invariant soliton equations from non-stretching geometric curve flows
A moving frame formulation of geometric non-stretching flows of curves in the
Riemannian symmetric spaces and is
used to derive two bi-Hamiltonian hierarchies of symplectically-invariant
soliton equations. As main results, multi-component versions of the sine-Gordon
(SG) equation and the modified Korteweg-de Vries (mKdV) equation exhibiting
invariance are obtained along with their bi-Hamiltonian
integrability structure consisting of a shared hierarchy of symmetries and
conservation laws generated by a hereditary recursion operator. The
corresponding geometric curve flows in and
are shown to be described by a non-stretching wave map and a
mKdV analog of a non-stretching Schr\"odinger map.Comment: 39 pages; remarks added on algebraic aspects of the moving frame used
in the constructio
The blackgrass genome reveals patterns of non-parallel evolution of polygenic herbicide resistance
Globally, weedy plants are a major constraint to sustainable crop production. Much of the success of weeds rests with their ability to rapidly adapt in the face of human-mediated management of agroecosystems. Alopecurus myosuroides (blackgrass) is a widespread and impactful weed affecting agriculture in Europe. Here we report a chromosome-scale genome assembly of blackgrass and use this reference genome to explore the genomic/genetic basis of non-target site herbicide resistance (NTSR). Based on our analysis of F2 seed families derived from two distinct blackgrass populations with the same NTSR phenotype, we demonstrate that the trait is polygenic and evolves from standing genetic variation. We present evidence that selection for NTSR has signatures of both parallel and non-parallel evolution. There are parallel and non-parallel changes at the transcriptional level of several stress- and defense-responsive gene families. At the genomic level, however, the genetic loci underpinning NTSR are different (non-parallel) between seed families. We speculate that variation in the number, regulation and function of stress- and defense-related gene families enable weedy species to rapidly evolve NTSR via exaptation of genes within large multi-functional gene families. These results provide novel insights into the potential for, and nature of plant adaptation in rapidly changing environments
RNA and protein biomarkers for detecting enhanced metabolic resistance to herbicides mesosulfuron-methyl and fenoxaprop-ethyl in black-grass (Alopecurus myosuroides)
BACKGROUND: The evolution of non-target site resistance (NTSR) to herbicides leads to a significant reduction in herbicide control of agricultural weed species. Detecting NTSR in weed populations prior to herbicide treatment would provide valuable information for effective weed control. While not all NTSR mechanisms have been fully identified, enhanced metabolic resistance (EMR) is one of the better studied, conferring tolerance through increased herbicide detoxification. Confirming EMR towards specific herbicides conventionally involves detecting metabolites of the active herbicide molecule in planta, but this approach is time consuming and requires access to well-equipped laboratories.
RESULTS: In this study, we explore the potential of using molecular biomarkers to detect EMR before herbicide treatment in black-grass (Alopecurus myosuroides). We test the reliability of selected biomarkers to predict EMR, and survival after herbicide treatments in both reference and 27 field-derived black-grass populations collected from sites across the UK. The combined analysis of the constitutive expression of biomarkers, and metabolism studies confirmed three proteins namely, AmGSTF1, AmGSTU2 and AmOPR1, as differential biomarkers of EMR toward the herbicides fenoxaprop-ethyl and mesosulfuron in black-grass.
CONCLUSION: Our findings demonstrate that there is potential to use molecular biomarkers to detect EMR toward specific herbicides in black-grass without reference to metabolism analysis. However, biomarker development must include testing at both transcript and protein levels in order to be reliable indicators of resistance. This work is a first step towards more robust resistance biomarker development, which could be expanded into other herbicide chemistries, for on-farm testing and monitoring EMR in uncharacterised black-grass populations
RNA and protein biomarkers for detecting enhanced metabolic resistance to herbicides mesosulfuron-methyl and fenoxaprop-ethyl in black-grass (<em>Alopecurus myosuroides</em>)
\ua9 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. BACKGROUND: The evolution of non-target site resistance (NTSR) to herbicides leads to a significant reduction in herbicide control of agricultural weed species. Detecting NTSR in weed populations prior to herbicide treatment would provide valuable information for effective weed control. While not all NTSR mechanisms have been fully identified, enhanced metabolic resistance (EMR) is one of the better studied, conferring tolerance through increased herbicide detoxification. Confirming EMR towards specific herbicides conventionally involves detecting metabolites of the active herbicide molecule in planta, but this approach is time-consuming and requires access to well-equipped laboratories. RESULTS: In this study, we explored the potential of using molecular biomarkers to detect EMR before herbicide treatment in black-grass (Alopecurus myosuroides). We tested the reliability of selected biomarkers to predict EMR and survival after herbicide treatments in both reference and 27 field-derived black-grass populations collected from sites across the UK. The combined analysis of the constitutive expression of biomarkers and metabolism studies confirmed three proteins, namely, AmGSTF1, AmGSTU2 and AmOPR1, as differential biomarkers of EMR toward the herbicides fenoxaprop-ethyl and mesosulfuron in black-grass. CONCLUSION: Our findings demonstrate that there is potential to use molecular biomarkers to detect EMR toward specific herbicides in black-grass without reference to metabolism analysis. However, biomarker development must include testing at both transcript and protein levels in order to be reliable indicators of resistance. This work is a first step towards more robust resistance biomarker development, which could be expanded into other herbicide chemistries for on-farm testing and monitoring EMR in uncharacterised black-grass populations. \ua9 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry
Integrable generalizations of Schrodinger maps and Heisenberg spin models from Hamiltonian flows of curves and surfaces
A moving frame formulation of non-stretching geometric curve flows in
Euclidean space is used to derive a 1+1 dimensional hierarchy of integrable
SO(3)-invariant vector models containing the Heisenberg ferromagnetic spin
model as well as a model given by a spin-vector version of the mKdV equation.
These models describe a geometric realization of the NLS hierarchy of soliton
equations whose bi-Hamiltonian structure is shown to be encoded in the Frenet
equations of the moving frame. This derivation yields an explicit
bi-Hamiltonian structure, recursion operator, and constants of motion for each
model in the hierarchy. A generalization of these results to geometric surface
flows is presented, where the surfaces are non-stretching in one direction
while stretching in all transverse directions. Through the Frenet equations of
a moving frame, such surface flows are shown to encode a hierarchy of 2+1
dimensional integrable SO(3)-invariant vector models, along with their
bi-Hamiltonian structure, recursion operator, and constants of motion,
describing a geometric realization of 2+1 dimensional bi-Hamiltonian NLS and
mKdV soliton equations. Based on the well-known equivalence between the
Heisenberg model and the Schrodinger map equation in 1+1 dimensions, a
geometrical formulation of these hierarchies of 1+1 and 2+1 vector models is
given in terms of dynamical maps into the 2-sphere. In particular, this
formulation yields a new integrable generalization of the Schrodinger map
equation in 2+1 dimensions as well as a mKdV analog of this map equation
corresponding to the mKdV spin model in 1+1 and 2+1 dimensions.Comment: Published version with typos corrected. Significantly expanded
version of a talk given by the first author at the 2008 BIRS workshop on
"Geometric Flows in Mathematics and Physics
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