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145 results on '"LaFountain, Amy M."'

12. To stripe or not to stripe: the origin of a novel foliar pigmentation pattern in monkeyflowers (Mimulus).

Author

LaFountain, Amy M., McMahon, Hayley E., Reid, Noah M., and Yuan, Yao‐Wu

Subjects
*MOLECULAR probes, *GENE expression, *STRIPES, *GENOME-wide association studies, *PHENOTYPES, *MUTAGENESIS
Abstract

Summary: The origin of phenotypic novelty is one of the most challenging problems in evolutionary biology. Although genetic regulatory network rewiring or co‐option has been widely recognised as a major contributor, in most cases how such genetic rewiring/co‐option happens is completely unknown.We have studied a novel foliar pigmentation pattern that evolved recently in the monkeyflower species Mimulus verbenaceus. Through genome‐wide association tests using wild‐collected samples, experimental crosses of laboratory inbred lines, gene expression analyses, and functional assays, we identified an anthocyanin‐activating R2R3‐MYB gene, STRIPY, as the causal gene triggering the emergence of the discrete, mediolateral anthocyanin stripe in the M. verbenaceus leaf.Chemical mutagenesis revealed the existence of upstream activators and repressors that form a 'hidden' prepattern along the leaf proximodistal axis, potentiating the unique expression pattern of STRIPY. Population genomics analyses did not reveal signatures of positive selection, indicating that nonadaptive processes may be responsible for the establishment of this novel trait in the wild.This study demonstrates that the origin of phenotypic novelty requires at least two separate phases, potentiation and actualisation. The foliar stripe pattern of M. verbenaceus provides an excellent platform to probe the molecular details of both processes in future studies. [ABSTRACT FROM AUTHOR]

Published
2023
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18. Emergence of a floral colour polymorphism by pollinator-mediated overdominance

Author

Kellenberger, Roman T, Byers, Kelsey J R P, De Brito Francisco, Rita M, Staedler, Yannick M, LaFountain, Amy M, Schönenberger, Jürg, Schiestl, Florian P, Schlüter, Philipp M, Kellenberger, Roman T, Byers, Kelsey J R P, De Brito Francisco, Rita M, Staedler, Yannick M, LaFountain, Amy M, Schönenberger, Jürg, Schiestl, Florian P, and Schlüter, Philipp M

Abstract

Maintenance of polymorphism by overdominance (heterozygote advantage) is a fundamental concept in evolutionary biology. In most examples known in nature, overdominance is a result of homozygotes suffering from deleterious effects. Here we show that overdominance maintains a non-deleterious polymorphism with black, red and white floral morphs in the Alpine orchid Gymnadenia rhellicani. Phenotypic, metabolomic and transcriptomic analyses reveal that the morphs differ solely in cyanidin pigments, which are linked to differential expression of an anthocyanidin synthase (ANS) gene. This expression difference is caused by a premature stop codon in an ANS-regulating R2R3-MYB transcription factor, which is heterozygous in the red colour morph. Furthermore, field observations show that bee and fly pollinators have opposite colour preferences; this results in higher fitness (seed set) of the heterozygous morph without deleterious effects in either homozygous morph. Together, these findings demonstrate that genuine overdominance exists in nature.

Published
2019

25. The intramolecular charge transfer state in carbonyl-containing polyenes and carotenoids

Author

Enriquez, Miriam M., Fuciman, Marcel, LaFountain, Amy M., Wagner, Nicole L., Birge, Robert R., and Frank, Harry A.

Subjects
Carbonyl compounds -- Structure, Carbonyl compounds -- Chemical properties, Carbonyl compounds -- Electric properties, Carotenoids -- Structure, Carotenoids -- Chemical properties, Carotenoids -- Electric properties, Charge transfer -- Analysis, Excited state chemistry -- Analysis, Molecular dynamics -- Usage, Polyenes -- Structure, Polyenes -- Chemical properties, Solvation -- Analysis, Chemicals, plastics and rubber industries
Published
2010

27. Ultrafast time-resolved carotenoid to-bacteriochlorophyll energy transfer in LH2 complexes from photosynthetic bacteria

Author

Hong Cong, Niedzwiedzki, Dariusz M., Gibson, George N., Lafountain, Amy M., Gardiner, Alastair T., Cogdell, Richard J., and Frank, Harry A.

Subjects
Bacteria, Photosynthetic -- Properties, Bacteria, Photosynthetic -- Research, Energy transformation -- Research, Chemicals, plastics and rubber industries
Abstract

A steady-state and ultrafast time-resolved spectroscopic examination is presented at room and cryogenic temperatures of four different LH2 pigment-protein complexes containing the Cars, neurosporene, spheroidene, or rhodopin glucoside. This study has resolved the question regarding the cause of the precipitous drop in energy transfer efficiency when the extent of [pi]-electron conjugation of the carotenoid is extended from ten to eleven conjugated carbon-carbon double bonds in LH2 complexes from purple photosynthetic bacteria.

Published
2008

42. Origin of the Bathochromic Shift of Astaxanthin in Lobster Protein: 2D Electronic Spectroscopy Investigation of beta-Crustacyanin

Author

Christensson, Niklas, Zidek, Karel, Magdaong, Nikki Cecil M., LaFountain, Amy M., Frank, Harry A., Zigmantas, Donatas, Christensson, Niklas, Zidek, Karel, Magdaong, Nikki Cecil M., LaFountain, Amy M., Frank, Harry A., and Zigmantas, Donatas

Abstract

We report on ultrafast spectroscopy study of beta-crustacyanin, the carotenoprotein responsible for the coloration of the lobster shell. beta-Crustacyanin is formed by two closely positioned astaxanthin molecules encapsulated in protein. The 2D electronic spectroscopy together with two-color pump-probe was applied to investigate the electronic structure, the excited-state dynamics, and the influence of the excitonic interaction between the two carotenoids in beta-crustacyanin. By using the similar to 20 Is laser pulses tuned to absorption bands of the S-0-S-2 and S-1-S-n transitions of carotenoids, we were able to trace full excitation relaxation dynamics, starting with S-2-S-1 relaxation on the similar to 30 fs time scale and finishing with the ground-state recovery of 3.2 ps. Superimposed on the relaxation dynamics in the 2D spectra, we observed long-lived beating signals at the characteristic frequencies of astaxanthin vibrational modes. We assign these oscillations to the ground-state vibrational wavepacket dynamics. All major features of the 2ll spectra, including amplitude and phase maps of the long-lived oscillations, were reproduced by employing the exciton-vibronic model. Consistent modeling of all optical properties of beta-crustacyanin (including absorption and circular dichroism spectra) points to the relatively weak coupling between the two astaxanthin molecules (similar to 250 cm(-1)). This implies that the excitonic coupling provides insignificant contribution to the bathochromic shift in beta-crustacyanin. We discuss the origin of the shift and propose that it is caused by two major effects: conformational changes of astaxanthin molecules (increase in effective conjugation length) together with increased charge-transfer character of the S-2 state. We put the bathochromic shift in the broad perspective of other "blue" carotenoids properties.

Published
2013

48. Spectroscopic Investigation of the Carotenoid Deoxyperidinin: Direct Observation of the Forbidden S0 → S1 Transition.

Author

Greco, Jordan A., LaFountain, Amy M., Naoto Kinashi, Tetsuro Shinada, Kazuhiko Sakaguchi, Shigeo Katsumura, Magdaong, Nikki Cecil M., Niedzwiedzki, Dariusz M., Birge, Robert R., and Frank, Harry A.

Subjects
*CAROTENOIDS, *CARBONYL group, *FUNCTIONAL groups, *ABSORPTION, *FLUORESCENCE spectroscopy
Abstract

This paper presents a spectroscopic investigation of deoxyperidinin, a synthetic peridinin analogue in which the carbonyl functional group in peridinin was replaced by a nonconjugated methylene group. Steady-state and ultrafast time-resolved absorption and fluorescence spectroscopic experiments are carried out on deoxyperidinin in n-hexane and acetonitrile at room temperature and in 2-methyltetrahydrofuran at 77 K. The spectra of deoxyperidinin have higher vibronic resolution compared to those of peridinin. The higher resolution is due to a substantial reduction in both molecular conformational disorder and inhomogeneous broadening of the spectra of deoxyperidinin compared to peridinin. Features in the steady-state absorption spectrum of deoxyperidinin that are not evident in the spectrum of peridinin are unambiguously assigned to the forbidden S0 (1¹Ag-) → S1 (2¹Ag-) absorption transition. The characteristics of both the steady-state and time-resolved spectra are interpreted using EOM-CCSD, SAC-CI, and MNDO-PSDCI quantum computational formalisms that provided a theoretical framework for understanding the photophysical properties of the molecules. [ABSTRACT FROM AUTHOR]

Published
2016
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49. An R2R3- MYB transcription factor regulates carotenoid pigmentation in Mimulus lewisii flowers.

Author

Sagawa, Janelle M., Stanley, Lauren E., LaFountain, Amy M., Frank, Harry A., Liu, Chang, and Yuan, Yao‐Wu

Subjects
CAROTENOIDS, TRANSCRIPTION factors, GENE expression in plants, PLANT molecular genetics, RNA interference
Abstract

Carotenoids are yellow, orange, and red pigments that contribute to the beautiful colors and nutritive value of many flowers and fruits. The structural genes in the highly conserved carotenoid biosynthetic pathway have been well characterized in multiple plant systems, but little is known about the transcription factors that control the expression of these structural genes., By analyzing a chemically induced mutant of Mimulus lewisii through bulk segregant analysis and transgenic experiments, we have identified an R2R3- MYB, Reduced Carotenoid Pigmentation 1 ( RCP1), as the first transcription factor that positively regulates carotenoid biosynthesis during flower development., Loss-of-function mutations in RCP1 lead to down-regulation of all carotenoid biosynthetic genes and reduced carotenoid content in M. lewisii flowers, a phenotype recapitulated by RNA interference in the wild-type background. Overexpression of this gene in the rcp1 mutant background restores carotenoid production and, unexpectedly, results in simultaneous decrease of anthocyanin production in some transgenic lines by down-regulating the expression of an activator of anthocyanin biosynthesis., Identification of transcriptional regulators of carotenoid biosynthesis provides the 'toolbox' genes for understanding the molecular basis of flower color diversification in nature and for potential enhancement of carotenoid production in crop plants via genetic engineering. [ABSTRACT FROM AUTHOR]

Published
2016
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