Arabidopsis seed germination speed is controlled by SNL histone deacetylase-binding factor-mediated regulation of AUX1

Histone acetylation is known to affect the speed of seed germination, but the molecular regulatory basis of this remains ambiguous. Here we report that loss of function of two histone deacetylase-binding factors, SWI-INDEPENDENT3 (SIN3)-LIKE1 (SNL1) and SNL2, results in accelerated radicle protrusion and growth during seed germination. AUXIN RESISTANT 1 (AUX1) is identified as a key factor in this process, enhancing germination speed downstream of SNL1 and SNL2. AUX1 expression and histone H3 acetylation at lysines 9 and 18 is regulated by SNL1 and SNL2. The D-type cyclins encoding genes CYCD1;1 and CYCD4;1 display increased expression in AUX1 over-expression lines and the snl1snl2 double mutant. Accordingly, knockout of CYCD4;1 reduces seed germination speed of AUX1 over-expression lines and snl1snl2 suggesting the importance of cell cycling for radicle protrusion during seed germination. Together, our work identifies AUX1 as a link between histone acetylation mediated by SNL1 and SNL2, and radicle growth promoted by CYCD1;1 and CYCD4;1 during seed germination.