Comparison of meiotic transcriptomes of three maize inbreds with different origins reveals differences in cell cycle and recombination

Authors: GRACIA, NELSON - University Of Minnesota; YIN, LU - Arizona State University; DUKOWIC-SCHULZE, STEFANIE - University Of Minnesota; MILSTED, CLAIRE - Arizona State University; KIANIAN, PENNY - University Of Minnesota; Kianian, Shahryar; PAWLOWSKI, WOJCIECH - Cornell University; CHEN, CHANGBIN - Arizona State University

Submitted to: BMC Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2022
Publication Date: 10/12/2022
Citation: Gracia, N., Yin, L., Dukowic-Schulze, S., Milsted, C., Kianian, P.M., Kianian, S., Pawlowski, W.P., Chen, C. 2022. Comparison of meiotic transcriptomes of three maize inbreds with different origins reveals differences in cell cycle and recombination. BMC Genomics. 23. Article 702. https://doi.org/10.1186/s12864-022-08922-w.
DOI: https://doi.org/10.1186/s12864-022-08922-w

Interpretive Summary: Meiosis is essential for sexual reproductive eukaryotes, during which homologous chromosomes pair, recombine and segregate, resulting in haploid gametes after two rounds of cell divisions following one round of genome duplication. During meiosis, homologous recombination occurs where homologous chromosome segments exchange and crossovers are formed. Homologous recombination not only facilitates successful reproduction, but also gives rise to novel allelic combinations which are the basis of genetic diversity. To determine if gene expression patterns are different among maize lines at critical stages, an RNA-Seq experiment was performed on CML228 male meiocytes and compared with B73 and Mo17 male meiocyte data obtained previously. Genes such as Zyp1 and Zip4 playing a role in limiting class I cross over formation were up-regulated in CML228 while Mus81 playing a role in promoting class II cross overs was down-regulated in CML228. Results suggest a possible link between differential expression of certain cellular processes and environmental stress such as heat, particularly in relation to homologous recombination. The link between environmental stress and DSB-induced repair requires further study.

Technical Abstract: Background: Cellular events during meiosis can differ between inbred lines in maize. Substantial differences in the average number of chiasmata and double-strand breaks per meiotic cell have been documented among CML228, a tropical maize inbred line, B73 and Mo17, temperate maize lines. To determine if gene expression might explain these observed differences, an RNA-Seq experiment was performed on CML228 male meiocytes which was compared to B73 and Mo17 male meiocytes. Results: Overall, the degree of similarity in expression patterns between the three maize lines reflect their genetic relatedness: B73 and Mo17 had similar meiotic expressions and CML228 had a more distinct expression profile. Many of the genes that were expressed at higher levels in CML228 were related to heat stress response such as membrane and localization genes. While genes involved in cell cycle related processes and replication-stress-mediated DNA repair were down-regulated in CML228. The expression of some of these genes were previously found to be specific to meiotic tissues. In addition, some but not all DSB-induced repair genes were up-regulated in CML228. Particularly, Zyp1 and Zip4 playing a role in limiting class I CO formation were up-regulated in CML228 while Mus81 playing a role in promoting class II CO formation was down-regulated in CML228. Conclusions: These results suggest a possible link between differential expression of these cellular processes and environmental stress such as heat, particularly in relation to homologous recombination. The link between environmental stress and DSB-induced repair seemed to be more complex and requires further study. The findings that the players playing a role in limiting class I CO formation (Zyp1 and Zip4) were up-regulated in CML228 and that the player Mus81 playing a role in promoting class II CO formation was down-regulated in CML228 might be linked to the lower CO number observed in CML228 previously. The results suggest a possible relationship between environment and meiotic recombination, which remains to characterized in more detail. In summary, we used natural maize inbred lines that have adapted to different climatic conditions and have shown their differences in expression landscape in male meiocytes.