Abstract
BackgroundRetrotransposons are heterogeneous sequences, widespread in eukaryotic genomes, which refer to the so-called mobile DNA. They resemble retroviruses, both in their structure and for their ability to transpose within the host genome, of which they make up a considerable portion. Copia- and Gypsy-like retrotransposons are the two main classes of retroelements shown to be ubiquitous in plant genomes. Ideally, the retrotransposons life cycle results in the synthesis of a messenger RNA and then self-encoded proteins to process retrotransposon mRNA in double stranded extra-chromosomal cDNA copies which may integrate in new chromosomal locations.ResultsThe RT-PCR and IRAP protocol were applied to detect the presence of Copia and Gypsy retrotransposon transcripts and of new events of integration in unstressed plants of a sunflower (Helianthus annuus L.) selfed line. Results show that in sunflower retrotransposons transcription occurs in all analyzed organs (embryos, leaves, roots, and flowers). In one out of sixty-four individuals analyzed, retrotransposons transcription resulted in the integration of a new element into the genome.ConclusionThese results indicate that the retrotransposon life cycle is firmly controlled at a post transcriptional level. A possible silencing mechanism is discussed.
Highlights
Retrotransposons are heterogeneous sequences, widespread in eukaryotic genomes, which refer to the so-called mobile DNA
Class I elements, which includes all REs, can transpose through a replicative mechanism which involves the transcription of an RNA intermediate by the enzyme machinery of the host cell, and subsequent retrotranscription to cDNA and integration into the host genome by the enzymes encoded by the retrotransposon RNA
Such a "copy and paste" mechanism has been largely successful during the evolution of eukaryotes in which class I elements represent the largest portion of higher plant genomes
Summary
Retrotransposons are heterogeneous sequences, widespread in eukaryotic genomes, which refer to the so-called mobile DNA. The mobile component of the genome is represented by sequences, called transposable elements (TEs), which are potentially able to change their chromosomal location (transposition) through different mechanisms This feature has a cladistic significance and TEs are subdivided into two main classes to their mechanism of transposition, retrotransposons (REs, class I) and DNA transposons (class II). Class I elements, which includes all REs, can transpose through a replicative mechanism which involves the transcription of an RNA intermediate by the enzyme machinery of the host cell, and subsequent retrotranscription to cDNA and integration into the host genome by the enzymes encoded by the retrotransposon RNA Such a "copy and paste" mechanism has been largely successful during the evolution of eukaryotes in which class I elements represent the largest portion of higher plant genomes. Non-autonomous elements do not carry enough coding capacity to allow them to transpose autonomously, they are able to move using enzymes encoded by other elements [2]
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