Rye B chromosomes encode a functional Argonaute-like proteinwith in vitro slicer activities similar to its A chromosome paralog

• Published in: The New phytologist 2017, Vol.213 (2), p.904
• Main Authors: Ma, Wei, Gabriel, Tobias Sebastian, Martis, Mihaela-Maria, Gursinsky, Torsten, Schubert, Veit, Vrana, Jan, Dolezel, Jaroslav, Gundlach, Heidrun, Altschmied, Lothar, Scholz, Uwe, Himmelbach, Axel, Behrens, Sven-Erik, Banaei-Moghaddam, Ali Mohammad, Houben, Andreas
• Format: Article
• Language: English
• Subjects: Argonaute; B chromosomes; B-located genes; gene erosion. gene expression; pseudogenization; Secale cereale
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.14110

B chromosomes (Bs) are supernumerary, dispensable parts of the nuclear genome, whichappear in many different species of eukaryote. So far, Bs have been considered to be geneti-cally inert elements without any functional genes. Our comparative transcriptome analysis and the detection of active RNA polymerase II(RNAPII) in the proximity of B chromatin demonstrate that the Bs of rye (Secale cereale) con-tribute to the transcriptome. In total, 1954 and 1218 B-derived transcripts with an open read-ing frame were expressed in generative and vegetative tissues, respectively. In addition to B-derived transposable element transcripts, a high percentage of short transcripts withoutdetectable similarity to known proteins and gene fragments from A chromosomes (As) werefound, suggesting an ongoing gene erosion process. In vitro analysis of the A- and B-encoded AGO4B protein variants demonstrated that bothpossess RNA slicer activity. These data demonstrate unambiguously the presence of a func-tional AGO4B gene on Bs and that these Bs carry both functional protein coding genes andpseudogene copies. Thus, B-encoded genes may provide an additional level of gene control and complexity incombination with their related A-located genes. Hence, physiological effects, associated withthe presence of Bs, may partly be explained by the activity of B-located (pseudo)genes.