Chong Sher Ney, Ravindran Pratibha, Kumar Prakash P
Department of Biological Sciences and Research Centre on Sustainable Urban Farming, Faculty of Science, National University of Singapore, 14 Science Drive 4, Singapore, 117543, Singapore.
A*STAR Infectious Diseases Labs (A*STAR IDL), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore.
Plant Cell Rep. 2025 Aug 1;44(8):188. doi: 10.1007/s00299-025-03582-y.
RGL2:DOF6 protein complex enhances BAT1 expression, which promotes primary seed dormancy in Arabidopsis, likely by inhibiting brassinosteroid biosynthesis. Hence, BAT1 acts as a novel gibberellin and brassinosteroid signaling crosstalk intermediate. A transcription factor complex including RGA-LIKE2 (RGL2) and DNA-BINDING ONE ZINC FINGER6 (DOF6) helps enforce primary seed dormancy. To elucidate the underlying mechanism by which the RGL2:DOF6 complex can enhance primary seed dormancy, we initiated a search for the downstream targets of this transcription complex. Using RNA sequence analysis, BRASSINOSTEROID-RELATED ACYLTRANSFERASE1 (BAT1) was identified to be a downstream target gene of the RGL2:DOF6 complex. Various genetic and molecular analyses were conducted using the mutant and overexpression lines. BAT1 is a known modulator of endogenous brassinosteroid (BR) levels. We observed that freshly harvested, unstratified bat1 mutant seeds germinated earlier, while BAT1 overexpression lines germinated later than the wild-type (WT) seeds. Consistently, dry-storage and cold-stratification of WT seeds, treatments that help to break dormancy, caused suppression of BAT1 expression levels. RT-qPCR and luciferase-based transcriptional assays showed that BAT1 expression could be enhanced by DOF6 in combination with RGL2 (i.e., by RGL2:DOF6 complex), a gibberellin (GA) signaling factor. BAT1 expression was also enhanced in abscisic acid (ABA)-treated seeds, which exhibit delayed germination. The function of BAT1 in sustaining primary seed dormancy is likely to occur via inhibition of BR biosynthesis because DOF6 overexpression seeds show suppression of BR biosynthetic genes (DWF1 and ROT3). Overall, these observations reveal that BAT1 serves as a crosstalk intermediate between BR and GA signaling pathways as one of the mechanisms in the regulation of primary seed dormancy.
RGL2:DOF6蛋白复合体增强了BAT1的表达，这可能通过抑制油菜素甾醇生物合成来促进拟南芥的初级种子休眠。因此，BAT1作为一种新的赤霉素和油菜素甾醇信号转导串扰中间体。一个包括类RGA2（RGL2）和DNA结合单锌指6（DOF6）的转录因子复合体有助于维持初级种子休眠。为了阐明RGL2:DOF6复合体增强初级种子休眠的潜在机制，我们开始寻找这个转录复合体的下游靶点。通过RNA序列分析，确定油菜素甾醇相关酰基转移酶1（BAT1）是RGL2:DOF6复合体的下游靶基因。利用突变体和过表达系进行了各种遗传和分子分析。BAT1是内源性油菜素甾醇（BR）水平的已知调节因子。我们观察到，新鲜收获的、未层积的bat1突变体种子发芽较早，而BAT1过表达系种子比野生型（WT）种子发芽晚。一致地，WT种子的干贮藏和冷层积处理有助于打破休眠，导致BAT1表达水平受到抑制。RT-qPCR和基于荧光素酶的转录分析表明，DOF6与RGL2（即RGL2:DOF6复合体）（一种赤霉素（GA）信号因子）联合可增强BAT1的表达。在脱落酸（ABA）处理的种子中，BAT1的表达也增强，这些种子表现出发芽延迟。BAT1在维持初级种子休眠中的功能可能是通过抑制BR生物合成来实现的，因为DOF6过表达种子显示出BR生物合成基因（DWF1和ROT3）受到抑制。总体而言，这些观察结果表明，BAT1作为BR和GA信号通路之间的串扰中间体，是调节初级种子休眠的机制之一。
