RNA Polymerases IV and V Are Involved in Olive Fruit Development

Abstract

Transcription is performed in most eukaryotes by three multimeric complexes (RNA polymer-ases I, II and III). However, plants contain two additional RNA polymerases (IV and V), which have evolved from RNA polymerase II. RNA polymerases II, IV and V contain both common and specific subunits that may specialize some of their functions. We herein searched for the genes that putatively code for the specific subunits of RNA polymerases IV and V, and the cor-responding of RNA polymerase II in olive. Based on the homology with the genes of Arabidop-sis thaliana, 13 genes that putatively code for the specific subunits of polymerases IV and V, and 16 genes that code for the corresponding specific subunits of polymerase II, were identified in olive. The expression analysis in different organs/tissues, biotic and abiotic stresses and a de-velopment process revealed that the expression of the RNA polymerases IV and V genes was induced during the initial fruit development steps. In lines with RNA polymerases IV and V in-volved in the transcription of long non-coding RNAs this induction was accompanied by rele-vant changes in expression of this type of RNAs. The expression of the intergenic and intronic long non-coding RNAs tended to increase in the early steps of developing fruit. These changes in the expression of long non-coding RNAs may be important for controlling gene expression during fruit development. In addition, some intergenic transcripts are susceptible to be pro-cessed and to become siRNAs, which are known to play a role in gene expression control. This reinforces the hypothesis that RNA polymerases IV and V may play a role in fruit development throughout the synthesis of long non-coding RNAs.