Browsing by Author "Katti, Christiana"
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Cloning of the opsin genes present in Bothrops atrox (Viperidae) retina(PUCE - Quito, 2017) Stacey Solís, Micaela; Katti, ChristianaThe visual system of vertebrates has evolved over millions of years to adapt to nocturnal or diurnal habits as well as different environments where varying spectral range and intensity of light are present. Although much is known about the visual system of vertebrates in general, studies about reptiles, and snakes in particular, are scarce. Reptiles display great diversity regarding their retinal structure, and different types of retinas exist (pure cone, mostly rod or duplex retina); however, the same five opsins are found in all of these animals. Because of their nocturnal and fossorial origins, snakes only have three of these visual opsins, namely: RH1 (rhodopsin-like 1) present in rods, LWS (long10 wavelength sensitive), and SWS1 (short-wavelength sensitive 1) that are present in cones. The study of snakes´ opsins has been largely ignored in the past; however, its importance has become clear within the past few years, and studies which reconsider Wall´s transmutation theory, proposed back in 1934, have emerged. In this study, we cloned the full length of RH1 and LWS opsins, as well of a part of the SWS1 opsin present in Bothrops atrox and have used these sequences to predict the Maximal absorbance (λmax) for each protein. This is the first report focusing on viper opsins; we report the first full length sequences available for opsins of this family, which has been poorly studied so far.Item Metadata only The diversity and adaptive evolution of visual photopigments in reptiles(2019-11-11) Katti, Christiana; Katti, ChristianaReptiles are a highly diverse class that consists of snakes, geckos, iguanid lizards, and chameleons among others. Given their unique phylogenetic position in relation to both birds and mammals, reptiles are interesting animal models with which to decipher the evolution of vertebrate photopigments (opsin protein plus a light-sensitive retinal chromophore) and their contribution to vision. Reptiles possess different types of retinae that are defined primarily by variations in photoreceptor morphology, which range from pure-cone to rod-dominated retinae with many species possessing duplex (rods and cones) retinae. In most cases, the type of retina is thought to reflect both the lifestyle and the behavior of the animal, which can vary between diurnal, nocturnal, or crepuscular behavioral activities. Reptiles, and in particular geckos and snakes, have been used as prime examples for the “transmutation” hypothesis proposed by Walls in the 1930s-1940s, which postulates that some reptilian species have migrated from diurnality to nocturnality, before subsequently returning to diurnal activities once again. This theory further states that these behavioral changes are reflected in subsequent changes in photoreceptor morphology and function from cones to rods, with a return to cone-like photoreceptors once again. Modern sequencing techniques have further investigated the “transmutation” hypothesis by using molecular biology to study the phototransduction cascades of rod- and cone-like photoreceptors in the reptilian retina. This review will discuss what is currently known about the evolution of opsin-based photopigments in reptiles, relating habitat to photoreceptor morphology, as well as opsin and phototransduction cascade gene expression.Item Metadata only Identificación de las proteínas visuales en reptiles ecuatorianosKatti, ChristianaLa Escuela Superior Politécnica del Litoral, impulsando la sociedad del conocimiento, mediante la Facultad de Ciencias de la Vida encargada de organizar las cuadragésimas XL Jornadas Nacionales de Biología, evento promocionado por la Sociedad Ecuatoriana de Biología y que se constituye como el más importante espacio para la difusión de la investigación e innovación en el área de las Ciencias de la Vida; a realizarse desde el 16 al 18 de noviembre de 2016 en el Campus Prosperina de la ESPOL, en el Auditorio del Centro de Información Bibliotecario y cuenta con la participación de investigadores nacionales e internaciones en las temáticas antes escritas, con el horario de 09h00 hasta las 18h00.Item Metadata only Opsin-based photopigments expressed in the retina of a South American pit viper, Bothrops atrox (Viperidae)(2018-12) Katti, Christiana; Katti, ChristianaAlthough much is known about the visual system of vertebrates in general, studies regarding vision in reptiles, and snakes in particular, are scarce. Reptiles display diverse ocular structures, including different types of retinae such as pure cone, mostly rod, or duplex retinas (containing both rods and cones); however, the same five opsin-based photopigments are found in many of these animals. It is thought that ancestral snakes were nocturnal and/or fossorial, and, as such, they have lost two pigments, but retained three visual opsin classes. These are the RH1 gene (rod opsin or rhodopsin-like-1) expressed in rods and two cone opsins, namely LWS (long-wavelength-sensitive) and SWS1 (short-wavelength-sensitive-1) genes. Until recently, the study of snake photopigments has been largely ignored. However, its importance has become clear within the past few years as studies reconsider Walls’ transmutation theory, which was first proposed in the 1930s. In this study, the visual pigments of Bothrops atrox (the common lancehead), a South American pit viper, were examined. Specifically, full-length RH1 and LWS opsin gene sequences were cloned, as well as most of the SWS1 opsin gene. These sequences were subsequently used for phylogenetic analysis and to predict the wavelength of maximum absorbance (λmax) for each photopigment. This is the first report to support the potential for rudimentary color vision in a South American viper, specifically a species that is regarded as being nocturnal.