Abstract
HSI2 and HSL1 are B3 domain transcriptional repressors of Arabidopsis thaliana. Seeds of double knockouts of hsi2 and hsl1 (KK mutant) obtained by a cross express seed maturation genes about 4 days after germination, accumulate seed storage proteins and oil in swollen hypocotyls, and stop growth 7 days after germination. To understand the mechanisms by which HSI2 and HSL1 repress the seed maturation program after germination, we introduced dexamethasone (DEX)-inducible RNAi for HSL1 in hsi2 mutant (HSL1-RNAi) and DEX-inducible RNAi for HSI2 in hsl1 mutant (HSI2-RNAi). Although germination of seeds of both transformants in the presence of DEX caused swelling of hypocotyls and severe growth retardation, DEX-induced gene expression pattern of HSL1-RNAi was more similar to that observed in KK mutants. We are also examining the possibility that B3 domain of HSI2 recognize RY motif in the promoters of many seed maturation genes.
