Cytomixis in wheat male meiosis: influence analysis of the substitution of chromosome 1A, 2D, 5A, or 5D

Cytomixis is a process of intercellular nuclear migration (INM) often observable in plant male meiosis. The genes responsible for this phenomenon have not been discovered yet. In an attempt to identify a cytomictic chromosome, we studied the male meiosis of wheat-rye single-chromosome substitution lines. Markers of the chromatin state were analyzed to figure out the nature of INM in cereal plants: is it a rather normal process or a consequence of random injury/deviation? There were no obvious correlations between the loss of wheat chromosome 1A, 2D, 5A, or 5D by hybrid plants and the frequency and cytological picture of INM in their meiosis. Acquisition of rye chromosome 1 Rv, 2 R, or 5 R did not correlate with any changes in the manifestation of INM either. Some unusual cytological patterns of the substituted-chromosome behavior were observed during INM. Chromosomes 1Rv, 2 R, and 5 R, which are alien to the wheat genome, were found to migrate preferentially between meiocytes. Analysis of post-translational histone modifications and synaptonemal-complex formation revealed that the migrating chromatin does not differ from the intact one. It is not inactivated, is properly condensed, and forms bivalents. Our findings suggest that none of the studied chromosomes carry cytomictic genes. At the same time, INM in male meiosis of cereals appears to be a normal process that may be involved in hybrid-genome rearrangements.

Automated summary

Cytomixis is a common phenomenon in plant male meiosis, and through the study of wheat-rye single-chromosome substitution lines, it was found that cytomixis is not correlated with the chromatin state. The rye chromosomes tend to migrate between meiocytes and the migrating chromatin is similar to intact chromatin. This suggests that cytomixis is a normal process that may be involved in hybrid-genome rearrangements.