Copia-like retrotransposons in a precocious mutant of trifoliate orange [Poncirus trifoliata (L.) Raf

Abstract

SummaryRetrotransposons are known to be involved in genetic instability in Citrus. The presence of copia-like retrotransposons was investigated in a precocious trifoliate orange (PTO) accession, a mutant that can flower and set fruit in 1-year-old seedlings. Ten copia-like reverse transcriptase (RT) fragments were cloned from its genome. The predicted amino acid sequences of these fragments showed that they shared the typical conservative and diverse properties of copia-like retrotransposons, and were divided into two sub-groups. Genomic hybridisation using one of the fragments (RT7) as a probe showed an extra copy was present exclusively in PTO. Inverse sequence tagged repeat (ISTR) analysis based on copia-like retrotransposon fingerprints detected two extra bands, and one band missing, in PTO. Despite the lack of transcriptional activity in the flowers and leaves of PTO, our results suggest that new transposition of copia-like retrotransposons has occurred in PTO, which might be related to the precocious trait of this mutant.