*email: nasuda.shuhei.5z@kyoto-u.ac.jp , yamamori.koichi.2k@kyoto-u.ac.jp

Gametocidal (Gc) genes in wheat are selfish genetic factors that preferentially transmit themselves to progeny by inducing chromosome breakage in the gametes lacking them. Gc genes are carried by the Gc chromosomes derived from Aegilops spp., and induce chromosome breakage during the first pollen mitosis when introduced hemizygously into the bread wheat genome. So far, at least five Gc genes have been reported and none of their responsible genes have been identified.

In this study, single-cell RNA-seq (scRNA-seq) analysis was performed on single pollen grains isolated from anthers at a post-meiotic stage. By comparing the expression profiles of each pollen, we intended to detect changes in the expression patterns related to the chromosome breakage induced by the Gc gene. In total 32 pollen grains from the Gc2 nulli- (hereafter, Gc2-null, n = 8), hemi- (Gc2-hemi, n = 16) and homo-zygous (Gc2-homo, n = 8) lines in the ‘Fielder’ background were analyzed by scRNA-seq. Chromosome breakage is expected to occur in a half of the pollen derived from Gc2-hemi, but not in Gc2-null and Gc2-homo.

Analysis of transcriptome patterns by UMAP (uniform manifold approximation and projection) for dimension reduction indicated that gene expression patterns of the pollen grains were largely classified into two groups; pollen grains from Gc2-null and Gc2-homo formed a group and all the pollen grains from Gc2-hemi formed another group. Within the Gc2-hemi group, pollen grains were further classified into two subgroups. We presume one subgroup corresponds to the pollen with chromosome breakage and the other to the ones without it.

To examine the characteristics of the pollen groups indicated by UMAP, we screened for the differentially expressed genes (DEGs) among the groups. In a comparison between pollen of Gc2-hemi and the other lines, the DEGs related to histone and genome stability were detected. Moreover, differences in expression levels of the histone-related genes were observed in a comparison between the two subgroups of pollen from Gc2-hemi.

This study was in part supported by Cabinet Office, Government of Japan, Moonshot R&D Program.