TY - JOUR
T1 - B chromosomes showing active ribosomal RNA genes contribute insignificant amounts of rRNA in the grasshopper Eyprepocnemis plorans
AU - Ruiz-Estévez, Mercedes
AU - Badisco, Liesbeth
AU - Broeck, Jozef Vanden
AU - Perfectti, Francisco
AU - López-León, María Dolores
AU - Cabrero, Josefa
AU - Camacho, Juan Pedro M.
N1 - Publisher Copyright:
© 2014, Springer-Verlag Berlin Heidelberg.
PY - 2014/11/19
Y1 - 2014/11/19
N2 - The genetic inertness of supernumerary (B) chromosomes has recently been called into question after finding several cases of gene activity on them. The grasshopper Eyprepocnemis plorans harbors B chromosomes containing large amounts of ribosomal DNA (rDNA) units, some of which are eventually active, but the amount of rRNA transcripts contributed by B chromosomes, compared to those of the standard (A) chromosomes, is unknown. Here, we address this question by means of quantitative PCR (qPCR) for two different ITS2 amplicons, one coming from rDNA units located in both A and B chromosomes (ITS2A+B) and the other being specific to B chromosomes (ITS2B). We analyzed six body parts in nine males showing rDNA expression in their B chromosomes in the testis. Amplification of the ITS2B amplicon was successful in RNA extracted from all six body parts analyzed, but showed relative quantification (RQ) values four orders of magnitude lower than those obtained for the ITSA+B amplicon. RQ values differed significantly between body parts for the two amplicons, with testis, accessory gland and wing muscle showing threefold higher values than head, gastric cecum and hind leg. We conclude that the level of B-specific rDNA expression is extremely low even in individuals where B chromosome rDNA is not completely silenced. Bearing in mind that B chromosomes carry the largest rDNA cluster in the E. plorans genome, we also infer that the relative contribution of B chromosome rRNA genes to ribosome biogenesis is insignificant, at least in the body parts analyzed.
AB - The genetic inertness of supernumerary (B) chromosomes has recently been called into question after finding several cases of gene activity on them. The grasshopper Eyprepocnemis plorans harbors B chromosomes containing large amounts of ribosomal DNA (rDNA) units, some of which are eventually active, but the amount of rRNA transcripts contributed by B chromosomes, compared to those of the standard (A) chromosomes, is unknown. Here, we address this question by means of quantitative PCR (qPCR) for two different ITS2 amplicons, one coming from rDNA units located in both A and B chromosomes (ITS2A+B) and the other being specific to B chromosomes (ITS2B). We analyzed six body parts in nine males showing rDNA expression in their B chromosomes in the testis. Amplification of the ITS2B amplicon was successful in RNA extracted from all six body parts analyzed, but showed relative quantification (RQ) values four orders of magnitude lower than those obtained for the ITSA+B amplicon. RQ values differed significantly between body parts for the two amplicons, with testis, accessory gland and wing muscle showing threefold higher values than head, gastric cecum and hind leg. We conclude that the level of B-specific rDNA expression is extremely low even in individuals where B chromosome rDNA is not completely silenced. Bearing in mind that B chromosomes carry the largest rDNA cluster in the E. plorans genome, we also infer that the relative contribution of B chromosome rRNA genes to ribosome biogenesis is insignificant, at least in the body parts analyzed.
KW - B chromosome
KW - Gene expression
KW - qPCR
KW - rDNA
KW - rRNA genes
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U2 - 10.1007/s00438-014-0880-y
DO - 10.1007/s00438-014-0880-y
M3 - Article
C2 - 24997085
AN - SCOPUS:84916904320
SN - 1617-4615
VL - 289
SP - 1209
EP - 1216
JO - Molecular Genetics and Genomics
JF - Molecular Genetics and Genomics
IS - 6
ER -