Objective  Role of SlSIP1L12, an SIP1 subfamily gene of trihelix transcription factors, played in tomato seed germination was investigated.

  Method  Expressions under and responses to phytohormone and abiotic stress of SlSIP1L12 were tested by RT-PCR. The RNAi technology was used to suppress the SlSIP1L12 expression to reveal its function on the seed germination. ELISA was applied to detect the endogenous ABA contents in the seeds.

  Result   (1) The length of SlSIP1L12 was 1 125bp in AC⁺⁺ that encoded 374 amino acids. The phylogenetic analysis confirmed that SIP1 genes had indeed evolved in AC⁺⁺. (2) SlSIP1L12 was primarily expressed in the stems and mature leaves, and secondly, in the flowers and fruits. (3) The suppressed expression of SlSIP1L12 could be artificially induced by ABA or dehydration, which implied a close relationship between the gene and ABA. (4) The germination of the SlSIP1L12 transgenic seeds was faster and grew to longer radicles than control. (5) ABA contents were significantly reduced in the transgenic seeds 7d after germination.

  Conclusion  The downregulated SlSIP1L12 that stimulated germination of tomato seeds was postulated to be closely associated with the ABA response of the plant.