Two SEPALLATA MADS-Box Genes, and , Have Cooperative Functions Required for Sepal Development in Tomato.

MADS-box transcription factors have crucial functions in numerous physiological and biochemical processes during plant growth and development. Previous studies have reported that two MADS-box genes, and play important regulatory roles in the sepal development of tomato, respectively. However, the functional relationships between these two genes are still unknown. In order to investigate this, we simultaneously studied these two genes in tomato. Phylogenetic analysis showed that they were classified into the same branch of the SEPALLATA (SEP) clade. qRT-PCR displayed that both and transcripts are preferentially accumulated in sepals, and are increased with flower development. During sepal development, is increased but is decreased. Using the RNAi, tomato plants with reduced mRNA generated enlarged and fused sepals, while simultaneous inhibition of and led to larger (longer and wider) and fused sepals than that in -RNAi lines. qRT-PCR results exhibited that the transcripts of genes relating to sepal development, ethylene, auxin and cell expansion were dramatically changed in -RNAi sepals, especially in --RNAi sepals. Yeast two-hybrid assay displayed that SlMBP21 can interact with SlMBP21, SlAP2a, TAGL1 and RIN, and SlMADS1 can interact with SlAP2a and RIN, respectively. In conclusion, and cooperatively regulate sepal development in tomato by impacting the expression or activities of other related regulators or via interactions with other regulatory proteins.