光敏色素互作因子（PIFs）广泛存在于苔藓到被子植物中，并在植物从暗形态建成到光形态建成的转化过程中发挥关键调控作用。PIFs直接与靶基因启动子区域的顺式作用元件结合，调控基因表达，或者与其它调控因子形成复合物，共同调控靶基因表达，PIFs是基因转录调控网络中的核心，通过整合内部和外部的信号以实现对植物体生长发育的调控。植物激素脱落酸（Abscisic Acid，ABA）调控植物的生长发育和对逆境胁迫的响应。ABA信号通路的很多组分已经被鉴定出来。
越来越多的证据证明，ABA与PIFs转录因子家族在光信号通路、植物生长发育和环境适应性方面具有协同作用。但是PIFs转录因子调控ABA信号转导的具体机制并不清楚。
2020年4月，Biochemical and Biophysical Research Communications发表了题为“ Phytochrome-interacting factors regulate seedling growth through ABA signaling”的文章，为揭示PIFs转录因子调控ABA信号转导机制提供了重要线索。
研究结果
1. PIFs转录因子在拟南芥各器官中广泛表达并且受到ABA调控
通过RT-qPCR发现PIF1, PIF3, PIF4和PIF5在多种组织器官和发育阶段均有表达。ABA处理后，PIF1, PIF3和PIF4的表达水平升高，但是PIF5的表达受到抑制。
2. pif突变体在幼苗生长期对脱落酸不敏感
首先构建了pif1, pif3, pif4, pif5, pif3/4/5, pif1/3/4/5和pif1/3/4突变体并对突变效果进行了验证。将突变体和野生型种子在含有ABA的培养基中培养，与野生型相比，pif突变体在幼苗生长阶段，呈现出对ABA脱敏的表型。
3. 过表达PIF3和PIF5增强了幼苗对脱落酸的敏感性
为进一步验证PIFs转录因子在ABA信号通路中的作用，将PIF3和PIF5的过表达株系在ABA的培养基中培养，与野生型相比，过表达植株的生长受到明显抑制，呈现出对ABA超敏感的表型。
4. 通过DAP-seq分析在基因组水平上鉴定PIF3和PIF5转录因子在DNA上的结合位点
已经有多项研究，使用ChIP-seq，对PIFs转录因子在基因组水平的结合位点进行了鉴定，但是ChIP-seq方法受限于特异性抗体的质量，并且操作复杂，实验难度大。本研究使用了一种新的方法：DAP-seq（DNA亲和纯化测序）对PIF3和PIF5在基因组上结合位点进行了鉴定。最终鉴定出PIF的保守motif为G-box，与已有的研究结果一致，并且鉴定出一批ABA响应的基因是PIFs的下游靶基因，比如PYL3，PYL6, PYL12, SnRK2.2, CPK4, CPK6, ABI5, ABF3和KIN1。2020年2月，在Molecular Plant期刊上，使用酵母单杂交、EMSA等技术，证明PIF1、PIP4和PIF5能够结合到ABI5启动子区的G-box上（Qi et al., 2020）。DAP-Seq的结果，与此结果相互印证。本研究证明了DAP-seq的可行性和有效性。
讨论
该研究通过DAP-seq鉴定出很多与ABA相关的PIFs靶基因、参与ABA合成的基因通路以及ABA信号转导通路中的组分。揭示了PIFs参与ABA信号转导的机制并非简单的单向调节，还存在反馈调控闭环。
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