Publication: Análisis estructural y funcional del cromosoma B de centeno
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2021-05-07
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Universidad Complutense de Madrid
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Abstract
Los cromosomas B (Bs) son cromosomas accesorios que aparecen en adición al grupo estándar de cromosomas (As) y están presentes numerosas especies de plantas, animales y hongos. Los Bs al no ser esenciales, presentan gran número de polimorfismos tanto numéricos como estructurales. Los Bs se mantienen en las poblaciones mediante mecanismos de acumulación o impulso que les permiten transmitirse en frecuencias superiores a las esperadas. El mecanismo de acumulación en centeno, es postmeiótico y se denomina no disyunción.
La estructura de algunos Bs, como el de maíz, ha sido estudiada en detalle y ha permitido resolver distintos interrogantes sobre su origen, comportamiento en las divisiones celulares y transmisión; por ese motivo se decidió realizar un análisis estructural y funcional del B de centeno. Se realizó un mapa físico de alta resolución en el estadio de paquitena mediante Hibridación in situ Fluorescente (FISH) de las secuencias Bilby (retrotransposón específico de los centrómeros de centeno) ScCCS1, Sc192pb, ScCRW2, pBs301-1 y Sc6C6-3 (secuencias de centeno con homología a distintas regiones del retrotransposón centromérico de trigo CRW); CRRye (parte del retrotransposón centromérico CR específico de centeno); ScCL11-1 (retrotransposón de la familia Copia específico del B de centeno); ADN de orgánulos; Sc9c130, Sc21c67, Sc26c38, Sc55-3.FGA, Sc63-2.FGA, E3900 y D1100 (secuencias repetidas del brazo largo del B de centeno). Se observó que todas las secuencias centroméricas y pericentroméricas (salvo pBs301-1 y Sc6C6-3) se encontraban además en los bloques heterocromáticos 2 y 3 del brazo largo del B. El análisis funcional de estas secuencias en metafase I, mostró que la organización del centrómero del B es diferente a la de los As. Las secuencias específicas del brazo largo se encuentran en la región distal del mismo, ocupando los bloques 2, 3, 4, 5 y 6. ScCL11-1 es la única secuencia presente en las regiones centromérica y pericentroméricas (donde se produce la no disyunción) y en el bloque 6 (región controladora de la no disyunción). Por otra parte, el ADN de orgánulos se localiza en regiones centroméricas y pericentroméricas, así como en los bloques 1, 2, 3 y 4...
B Chromosomes (Bs) are accessory chromosomes that appear in addition to the standard set of chromosomes (As). They are present in numerous species of plants, animals, and fungi. Bs are maintained in populations by accumulation or impulse mechanisms, allowing them to be transmitted at higher than expected frequencies. In grasses, the accumulation mechanism is postmeiotic, and it is called nondisjunction. Furthermore, as B chromosomes are not essential, they show a large number of both numerical and structural polymorphisms. Studies of the maize B structure have allow to solve questions about its origin, behaviour and transmission; for that reason, it was decided to carry out a structural and functional analysis of rye B. High-resolution mapping was performed by Fluorescent in situ Hybridization (FISH) at pachytene with following probes: Bilby (retrotransposon specific of rye centromeres); ScCCS1, Sc192pb, ScCRW2, pBs301-1 and Sc6C6-3 (rye sequences with homology to different regions of the wheat centromeric retrotransposon CRW); CRRye (CR centromeric retrotransposon specific of rye) ; ScCL11-1 (Copia retrotransposon specific of the rye B); Organellar DNA; Sc9c130, Sc21c67, Sc26c38, Sc55-3.FGA, Sc63-2.FGA, E3900 and D1100 (repeat sequences of the long arm of rye B). All the centromeric and pericentromeric sequences (except pBs301-1 and Sc6C6-3) were also found in heterochromatic blocks 2 and 3. The functional analysis of these same sequences at metaphase I has revealed that the organization of the B centromere is different to As centromeres. The specific sequences of the long arm are found in the distal region of the arm, occupying blocks 2, 3, 4, 5 and 6. ScCL11-1 is the only sequence present in the centromeric and pericentromeric regions (nondisjunction region) and in block 6 (nondisjunction controlling region). On the other hand, organellar DNA is located in the centromeric and pericentromeric regions, as well as in blocks 1, 2, 3 and 4. Most of the centromeric sequences are also found in an interstitial region of the long arm, which suggest a dicentric origin for the rye B; however, no CENH3 signal was seen outside the centromere...
B Chromosomes (Bs) are accessory chromosomes that appear in addition to the standard set of chromosomes (As). They are present in numerous species of plants, animals, and fungi. Bs are maintained in populations by accumulation or impulse mechanisms, allowing them to be transmitted at higher than expected frequencies. In grasses, the accumulation mechanism is postmeiotic, and it is called nondisjunction. Furthermore, as B chromosomes are not essential, they show a large number of both numerical and structural polymorphisms. Studies of the maize B structure have allow to solve questions about its origin, behaviour and transmission; for that reason, it was decided to carry out a structural and functional analysis of rye B. High-resolution mapping was performed by Fluorescent in situ Hybridization (FISH) at pachytene with following probes: Bilby (retrotransposon specific of rye centromeres); ScCCS1, Sc192pb, ScCRW2, pBs301-1 and Sc6C6-3 (rye sequences with homology to different regions of the wheat centromeric retrotransposon CRW); CRRye (CR centromeric retrotransposon specific of rye) ; ScCL11-1 (Copia retrotransposon specific of the rye B); Organellar DNA; Sc9c130, Sc21c67, Sc26c38, Sc55-3.FGA, Sc63-2.FGA, E3900 and D1100 (repeat sequences of the long arm of rye B). All the centromeric and pericentromeric sequences (except pBs301-1 and Sc6C6-3) were also found in heterochromatic blocks 2 and 3. The functional analysis of these same sequences at metaphase I has revealed that the organization of the B centromere is different to As centromeres. The specific sequences of the long arm are found in the distal region of the arm, occupying blocks 2, 3, 4, 5 and 6. ScCL11-1 is the only sequence present in the centromeric and pericentromeric regions (nondisjunction region) and in block 6 (nondisjunction controlling region). On the other hand, organellar DNA is located in the centromeric and pericentromeric regions, as well as in blocks 1, 2, 3 and 4. Most of the centromeric sequences are also found in an interstitial region of the long arm, which suggest a dicentric origin for the rye B; however, no CENH3 signal was seen outside the centromere...
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Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Biológicas, Departamento de Genética, Fisiología y Microbiología, leída el 13/01/2021