Antagonistic action of TILLERS ABSENT1 and FLORAL ORGAN NUMBER2 regulates stem cell maintenance during axillary meristem development in rice

Summary Shoot branches are formed from the axillary meristem and their formation is a key process in plant development. Although our understanding of the mechanisms underlying stem cell maintenance in the shoot apical meristem ( SAM ) is progressing, our knowledge of these mechanisms during the process of axillary meristem development is insufficient. To elucidate the genetic mechanisms underlying axillary meristem development in rice ( Oryza sativa ), we undertook a molecular genetic analysis focusing on TILLERS ABSENT 1 ( TAB 1 ) and FLORAL ORGAN NUMBER 2 ( FON 2 ), respective orthologs of the WUSCHEL and CLAVATA 3 genes involved in SAM maintenance in Arabidopsis ( Arabidopsis thaliana ). We revealed that stem cells were established at an early stage of axillary meristem development in the wild‐type, but were not maintained in tab1 . By contrast, the stem cell region and TAB 1 expression domain were expanded in fon2 , and FON 2 overexpression inhibited axillary meristem formation. These results indicate that TAB 1 is required to maintain stem cells during axillary meristem development, whereas FON 2 negatively regulates stem cell fate by restricting TAB 1 expression. Thus, the genetic pathway regulating SAM maintenance in Arabidopsis seems to have been recruited to play a specific role within a narrow developmental window – namely, axillary meristem establishment – in rice.