Physical localization and probable transcriptional activity of 18S–5.8S–26S rRNA gene loci in some Asiatic Cymbidiums (Orchidaceae) from north-east India

• Published in: Gene Vol. 499; no. 2; pp. 362 - 366
• Main Authors: Sharma, Santosh Kumar, Mehra, Poonam, Kumari, Jyoti, Kumar, Sundip, Kumaria, Suman, Tandon, Pramod, Rao, Satyawada Rama
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.05.2012
• Subjects: cell nucleolus; Cymbidium; epigenetics; evolution; FISH; fluorescence; fluorescence in situ hybridization; genes; Genes, Plant; Genes, rRNA; In Situ Hybridization, Fluorescence; India; loci; Orchidaceae; Orchidaceae - genetics; ploidy; rDNA; ribosomal DNA; ribosomal RNA; RNA, Ribosomal - genetics; transcription (genetics); Transcription, Genetic; Transcriptionally active; South East Asia; India; rDNA; Transcriptionally active; Orchidaceae; FISH; SPAR; ITS; Cymbidium
• ISSN: 0378-1119; 1879-0038
• DOI: 10.1016/j.gene.2012.03.007

Fluorescence in situ hybridization based physical localization of 45S ribosomal DNA in eight horticulturally important species of Cymbidium (Orchidaceae) from north-east India (South-East Asia) has been carried for the first time. Observations revealed only one pair of chromosomes had NOR loci. Three, out of eight Cymbidiums showed decondensed, dispersed, extended form of hybridization signals of rDNA as dots of fluorescence (transcriptionally active), where as the rest of the Cymbidiums revealed condensed (non-active) forms, hence demonstrated the heteromorphism in size, intensities and their appurtenance which may be under epigenetic control. Except for the ribosomal genes, no other active genes have been reported to reside within the nucleoli. Such observations provide useful chromosome landmarks and provide valuable evidence about the genome evolution, speciation and ploidy both at molecular and chromosomal levels which is more or less highly ambiguous in family Orchidaceae. ► FISH based physical localization of 45S rDNA has been carried out in Cymbidiums. ► Results showed that Cymbidiums had only one pair of NOR loci. ► 3 Cymbidiums showed decondensed, dispersed, extended form of hybridization signals. ► Heteromorphic signals as dots of fluorescence may be transcriptionally active sites. ► Study offers valuable evidence for genome evolution, speciation and ploidy in orchids.