Prieto-Dapena Pilar, Carranco Raúl, Almoguera Concepción, Jordano Juan
Instituto de Recursos Naturales y Agrobiología de Sevilla, Consejo Superior de Investigaciones Científicas (IRNAS-CSIC), Sevilla, Spain.
Plant J. 2025 Jun;122(5):e70261. doi: 10.1111/tpj.70261.
HSFA9 (A9) is a seed-specific transcription factor that contributes to seed longevity in sunflower. A9 also links the regulation of seed maturation with that of early seedling greening through its effects on various light receptors. Transcriptomic analyses of transgenic tobacco seeds suggested that A9 might affect chromatin remodeling. Here, using formaldehyde-assisted isolation of regulatory elements (FAIRE) and micrococcal nuclease digestion, we analyzed the A9 effects on chromatin accessibility shortly after seed imbibition in the proximal promoter region of developmentally relevant genes, including HY5 and PHYA. A9, expressed from a seed-specific promoter, enhanced chromatin accessibility in the analyzed regions. Converse, promoter-specific, effects were observed upon loss-of-function of tobacco A9 (NtA9) in transgenic seeds. Furthermore, a memory effect was observed, as the induced chromatin accessibility persisted for up to 4 days after seed imbibition, when A9 was no longer detected. The A9-induced chromatin effects involved labile/unstable nucleosomes placed at proximal promoter locations where A9 induced substantial nucleosomal depletion. Specific inhibitors of BRAHMA-like ATPase subunits of SWI/SNF (SWItch/Sucrose Non-Fermentable) chromatin-remodeling complexes and histone deacetylase (HDAC) impaired A9-induced memory. Thus, SWI/SNF remodeling and HDAC activity mechanistically contribute to the A9-induced memory. Furthermore, SWI/SNF inhibition specifically reduced the HY5 and PHYA promoter accessibility in both transgenic and non-transgenic seeds. Our results identify HSFA9 as a potential master, short-term, 'epigenetic' regulator that operates in seeds in anticipation of seedling establishment. The new, A9-induced, somatic memory effect reported here may facilitate early seedling greening and stress tolerance during the seed-to-seedling developmental transition.
热激转录因子A9（HSFA9，简称A9）是一种种子特异性转录因子，对向日葵种子的寿命有重要作用。A9还通过影响多种光受体，将种子成熟调控与幼苗早期绿化联系起来。对转基因烟草种子的转录组分析表明，A9可能影响染色质重塑。在此，我们利用甲醛辅助调控元件分离（FAIRE）和微球菌核酸酶消化技术，分析了种子吸胀后不久A9对发育相关基因（包括HY5和PHYA）近端启动子区域染色质可及性的影响。从种子特异性启动子表达的A9增强了分析区域的染色质可及性。相反，在转基因种子中，烟草A9（NtA9）功能丧失时则观察到启动子特异性效应。此外，还观察到一种记忆效应，即当不再检测到A9时，诱导的染色质可及性在种子吸胀后持续长达4天。A9诱导的染色质效应涉及位于近端启动子位置的不稳定核小体，A9在这些位置诱导了大量核小体缺失。SWI/SNF（SWItch/Sucrose Non-Fermentable）染色质重塑复合体中类BRAHMA样ATP酶亚基和组蛋白去乙酰化酶（HDAC）的特异性抑制剂损害了A9诱导的记忆。因此，SWI/SNF重塑和HDAC活性在机制上对A9诱导的记忆有贡献。此外，SWI/SNF抑制特异性降低了转基因和非转基因种子中HY5和PHYA启动子的可及性。我们的研究结果表明，HSFA9是一种潜在的主要短期“表观遗传”调节因子，在种子中发挥作用，为幼苗建立做准备。本文报道的新的A9诱导的体细胞记忆效应可能有助于种子到幼苗发育转变过程中的早期幼苗绿化和胁迫耐受性。
