Shi H, Zhong S, Mo X, Liu N, Nezames CD, Deng XW

Seed germination is the first step for seed plants to initiate a new life cycle. Light plays a predominant role in promoting seed germination, where the initial phase is mediated by photoreceptor phytochrome B (phyB). Previous studies showed that PHYTOCHROME-INTERACTING FACTOR1 (PIF1) represses seed germination downstream of phyB. Here, we ...

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identify a positive regulator of phyB-dependent seed germination, LONG HYPOCOTYL IN FAR-RED1 (HFR1). HFR1 blocks PIF1 transcriptional activity by forming a heterodimer with PIF1 that prevents PIF1 from binding to DNA. Our whole-genomic analysis shows that HFR1 and PIF1 oppositely mediate the light-regulated transcriptome in imbibed seeds. Through the HFR1-PIF1 module, light regulates expression of numerous genes involved in cell wall loosening, cell division, and hormone pathways to initiate seed germination. The functionally antagonistic HFR1-PIF1 pair constructs a fail-safe mechanism for fine-tuning seed germination during low-level illumination, ensuring a rapid response to favorable environmental changes. This study identifies the HFR1-PIF1 pair as a central module directing the whole genomic transcriptional network to rapidly initiate light-induced seed germination.

Date: Oct. 31, 2013

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