SWI/SNF ATPase SPLAYED modulates ABA catabolism and GA biosynthesis in ABA-inhibition of seed germination
The phytohormone abscisic acid (ABA) promotes seed dormancy and inhibits seed germination and seedling development. It remains unclear how chromatin remodeling influences ABA responses. In the present study, an artificial microRNA targeting two Sucrose Non-Fermenting 2 (SNF2)-family chromatin remodeling ATPases, SPLAYED (SYD) and PHOTOPERIOD-INDEPENDENT EARLY FLOWERING1 (PIE1), was identified through unbiased forward genetic screenings of artificial microRNA (amiRNA)-expressing pooled seed libraries exhibiting ABA-insensitive seed germination. T-DNA insertional mutants of syd and pie1, along with amiRNA-expressing knockdown lines amiR-SYD and amiR-PIE1, confirmed that SYD, but not PIE1, is essential for promoting ABA-inhibition of seed germination. Transcriptome analyses revealed that the ABA catabolism gene CYP707A3 and the gibberellin (GA) biosynthesis genes GA20OX2, GA20OX3, GA3OX2, GA3OX3, and GA3OX4 were upregulated in amiR-SYD mutant seeds compared to control seeds under ABA treatment during germination. The ABA hyposensitivity observed in amiR-SYD mutants was reversed by treatment with uniconazole, an inhibitor of ABA catabolism and GA biosynthesis, suggesting that the reduced ABA sensitivity in amiR-SYD mutants results from increased ABA degradation and GA production. These findings demonstrate that the SYD-associated chromatin remodeling complex positively regulates ABA responses during seed germination, unlike its close homolog BRAHMA (BRM), which acts as a negative regulator of the ABA response. Overall design: Expression profiling of amiR-HsMYO control and amiR-SYD seeds germinated under control and ABA conditions for 24 hrs.