背景回顾：Pre-mRNA splicing is a crucial step in gene expression whereby the spliceosome produces constitutively and alternatively spliced transcripts. These transcripts not only diversify the transcriptome, but they also play essential roles in plant development and responses to environmental changes. 

提出问题：Much evidence indicates that regulation at the pre-mRNA splicing step is important for flowering time control; however, the components and detailed mechanism underlying this process remain largely unknown. 

主要发现：Here, we identified the splicing factor RNA BINDING PROTEIN 45d (RBP45d), a member of the RBP45/47 family in Arabidopsis thaliana. 

结果1-基因鉴定：Using sequence comparison and biochemical analysis, we determined that RBP45dis a component of the U1 small nuclear ribonucleoprotein (U1 snRNP) with functions distinct from other family members. 

结果2-RBP45d-PRP39a-U1 snRNP：RBP45d associates with the U1 snRNP by interacting with pre-mRNA-processing factor 39a (PRP39a) and directly regulates alternative splicing (AS) for a specific set of genes. 

结果3-功能缺失突变：Plants with loss of RBP45d and PRP39a function exhibited defects in temperature-induced flowering, potentially due to the misregulation of temperature-sensitive AS of FLOWERING LOCUS M as well as the accumulation of the flowering repressor FLOWERING LOCUS C. 

结论：Taken together, RBP45d is a U1 snRNP component in plants that functions with PRP39a in temperature-mediated flowering.

 摘 要 

前体mRNA剪切是基因表达的一个重要步骤，剪切体会产生两种类型的转录本，即组成型和可变剪切转录本。这些转录本不仅丰富了转录组的多样性，同时也在植物的发育极其对外界环境变化的响应过程中发挥重要作用。很多证据表明，前体RNA剪切步骤的调控对于开花时间调控是非常重要的；但是，该过程中参与者及具体的分子机制还不清楚。本文中，作者在拟南芥中鉴定到了RBP45/47家族的一个剪切因子RBP45d。利用序列比较和生化分析，作者发现RBP45d是U1核微小核糖核蛋白的一个组分，其功能不同于其所属家族的其它成员。RBP45d通过与前体mRNA加工因子PRP39a互作，从而参与U1 snRNP，直接调控某类特定基因的可变剪切。RBP45d和PRP39a功能缺失突变的植株在温度诱导的开花方面存在缺陷，直接原因是由于温度敏感基因FLM可变剪切的失调，以及开花抑制因子FLC的积累。综上，本文的研究揭示了RBP45d是植物中U1 snRNP的组分，与PRP39a一道作用于植物中温度介导的开花。