PT  - JOURNAL ARTICLE
AU  - Anlong Jiang
AU  - Zhonglong Guo
AU  - Jiawei Pan
AU  - Yan Zhuang
AU  - Daqing Zuo
AU  - Chen Hao
AU  - Zhaoxu Gao
AU  - Peiyong Xin
AU  - Jinfang Chu
AU  - Shangwei Zhong
AU  - Lei Li
TI  - The &lt;em&gt;PIF1-MIR408-Plantacyanin&lt;/em&gt; Repression Cascade Regulates Light Dependent Seed Germination
AID  - 10.1101/2020.07.20.212340
DP  - 2020 Jan 01
TA  - bioRxiv
PG  - 2020.07.20.212340
4099  - http://biorxiv.org/content/early/2020/07/21/2020.07.20.212340.short
4100  - http://biorxiv.org/content/early/2020/07/21/2020.07.20.212340.full
AB  - Light-sensing seed germination is a vital process for the seed plants. A decisive event in light-induced germination is degradation of the central repressor PHYTOCHROME INTERACTING FACTOR1 (PIF1). It is also known that the balance between gibberellic acid (GA) and abscisic acid (ABA) critically controls germination. But the cellular mechanisms linking PIF1 turnover to hormonal rebalancing remain elusive. Here, employing far-red light-induced Arabidopsis seed germination as the experimental system, we identified Plantacyanin (PLC) as an inhibitor of germination, which is a storage vacuole-associated blue copper protein highly expressed in mature seed and rapidly silenced during germination. Molecular analyses showed that PIF1 directly binds to the MIR408 promoter and represses miR408 accumulation, which in turn post-transcriptionally modulates PLC abundance, thus forming the PIF1-MIR408-PLC repression cascade for translating PIF1 turnover to PLC turnover during early germination. Genetic analysis, RNA-sequencing, and hormone quantification revealed that PLC is necessary and sufficient to maintain the PIF1-mediated seed transcriptome and the low-GA-high-ABA state. Furthermore, we found that PLC domain organization and regulation by miR408 are conserved features in seed plants. These results unraveled a cellular mechanism whereby PIF1-relayed external light signals are converted through PLC-based copper mobilization into internal hormonal profiles for controlling seed germination.