背景+问题：Hormone-like signaling peptides play essential roles in plant growth and development; however, few peptides regulating root development have been identified in rice (Oryza sativa). 

主要研究：Here, we combined liquid chromatography–tandem mass spectrometry (LC-MS/MS) with whole-genome in silico screening for root-secreted peptides in rice. 

结果1-PEP1鉴定：We identified the five-amino-acid PEPTIDE 1 (PEP1) encoded by OsPEP1 (LOC_Os11g09560).

结果2-OsPEP1表达模式：OsPEP1 was expressed highly in root tissues, especially root cap cells and epidermal cells in the root maturation zone. Exogenous application of PEP1 inhibited primary root growth. 

结果3-OsPEP1敲低表型：Notably, OsPEP1 RNA interference (RNAi) lines had short primary roots with small meristems and short cells in the root elongation zone; furthermore, the short root phenotype of OsPEP1 RNAi plants could be rescued by exogenous application of PEP1. 

结果4-转录组：Our transcriptome data further revealed that PEP1 could reprogram the expression of genes in different pathways, including oxidation–reduction.

结果5-OsPEP1过表达：OsPEP1 overexpression lines similarly displayed short roots, although this phenotype was not rescued by exogenous PEP1. 

结论：These results suggest that root growth can be inhibited by both too much and too little PEP1. Our findings highlight PEP1 as a candidate plant peptide hormone regulating root development in rice.

 摘 要 

类似于激素的信号转导多肽在植物的生长和发育中发挥重要作用；但是，目前鉴定的与水稻根发育调控相关的多肽很少。本文中，作者利用液相色谱-质谱/质谱（LC-MS/MS），结合全基因组范围的多肽生信预测，对水稻根分泌的多肽进行鉴定。作者鉴定到了一个由5个氨基酸组成的多肽OsPEP1，该多肽由水稻LOC_Os11g09560基因编码。OsPEP1在根组织中高表达，尤其是根成熟区的根冠细胞和表皮细胞。外源施加PEP1会抑制初生根的生长。值得注意的是，OsPEP1 RNA干扰（RNAi）株系初生根较短，分生组织较小，根伸长区的细胞长度较短；此外，外源施加PEP1可以拯救OsPEP1 RNAi株系的短根表型。进一步的转录组数据分析显示，PEP1重编程多个通路的基因转录表达，包括氧化还原途径。OsPEP1过表达株系同样表现出短根，但是外源施加PEP1不能拯救该表型。这些结果表明，过多和过少的PEP1都能抑制根系生长。本文的研究结果表明，PEP1是一种调节水稻根系发育的候选植物肽类激素。