Maize (Zea mays) is one of the world's most important crops and a recognized model for biological research, with some individuals having supernumerary B chromosomes. This B chromosome has been studied for decades, yet its gene expression across different plant tissues has not been thoroughly described. Here, we present a comprehensive transcriptomic atlas of the maize plant with and without the B chromosome. By analysing 11 tissues/organs, we found that genes encoded by the B chromosome contribute to the transcriptome throughout plant growth, with the highest activity observed in reproductive organs. Co-expression analysis revealed a cluster of 30 genes expressed specifically in tassels and indicated that Shortage in chiasmata 1 is a promising candidate for regulation of crossover frequency mediated by the B chromosome. In addition to its own transcriptional activity, our results also demonstrated that the B chromosome influences the expression of genes located on the A chromosome in all the tissues that we analysed. As well as providing new insights into the expression and regulatory effects of the B chromosome, our study has also generated fundamental information that will provide a basis for exploring its wider biological role.

Department of Cell Biology and Genetics Palacký University Šlechtitelů 27 Olomouc 779 00 Czech Republic

Institute of Experimental Botany of the Czech Academy of Sciences Centre of Plant Structural and Functional Genomics Šlechtitelů 31 Olomouc 779 00 Czech Republic

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