Abstract
The shoot-apical-meristem (SAM) of Arabidopsis is maintained primarily through two independent pathways by WUS and STM. However, mechanisms for transcriptional regulation of these regulators remain largely unknown. We isolated a T-DNA insertion mutant, sha1 (shoot-apical-meristem arrest 1) in Arabidopsis, in which the T-DNA is inserted in the 5, promoter region of the gene encoding a novel ring-finger protein SHA1. The vegetative SAM of sha1 appears normal during juvenile stage (JV), but becomes fasciated after entering adult stage (AV), and disappears completely at the stage when wildtype begins to bolting. Consequently, no primary inflorescence and floral primordia are formed in sha1. Gene expression analysis reveals that in sha1, CLV1, CLV2 and STM are not significantly altered during both JV and AV, while WUS and CLV3 remain unchanged during JV but are extremely reduced during AV. These results suggest that SHA1 is required for promoting WUS transcription in postembryonic SAM maintenance.
