Zea mays Raw sequence reads

Ubiquitination and deubiquitination are important post-translational regulations in eukaryotes. Recent studies in Arabidopsis showed that they could affect all plant growth and development aspects. However, there needed to be more knowledge about their involvement in maize kernel development.In this study, we worked on a novel EMS-induced maize kernel mutant ubp5, which had small and dark appearance, along with arrested embryo development and defectiveness in the endosperm. Through gene mapping and allelic verification, we identified that ZmUBP5 with c.1372C>T|p.Q458* mutation was the causal for this kernel mutant. ZmUBP5 was annotated as a ubiquitin-specific protease (UBP) with deubiquitinase activity, and it was localized to nuclear, while the stop_gained mutation could disrupt this. Omics analysis showed that the ubp5 mutation affected transcriptome, proteome, and ubiquitinome in maize kernel developent at a global level. Through protein interaction and degradation experiments, we proved that ZmUBP5 could interact with and might regulate the ubiquitination level of ZmEMB140. ZmEMB140 was annotated as a spliceosome-associated protein essential for splicing. Maize mutant with a stop_gained mutation (c.652C>T|p.Q218*) in ZmEMB140 showed smaller kernel size with smaller embryos and endosperm. Furthermore, we proved that ZmEMB140 was involved in pre-mRNA processing by affecting alternative splicing. ZmEMB140 could interact with four U6 snRNA-associated Sm-like proteins (LSM) and two pre-mRNA processing factors (PRP).Our study revealed for the first time the mechanism by which deubiquitinase ZmUBP5 is involved in the regulation of maize kernel development.

泛素化（Ubiquitination）与去泛素化（deubiquitination）是真核生物中重要的翻译后调控方式。近期在拟南芥（Arabidopsis）中的研究表明，二者可影响植物生长发育的所有环节。然而，目前对于其参与玉米籽粒发育过程的认知仍较为匮乏。本研究针对一个新型乙基甲磺酸（EMS）诱变的玉米籽粒突变体ubp5展开探究，该突变体籽粒外观瘦小且色泽加深，同时伴随胚胎发育停滞与胚乳发育缺陷。通过基因定位与等位基因验证，我们鉴定出携带c.1372C>T|p.Q458*突变的ZmUBP5为导致该籽粒突变表型的因果基因。ZmUBP5被注释为具有去泛素化酶活性的泛素特异性蛋白酶（ubiquitin-specific protease, UBP），定位于细胞核，而该终止密码子获得型突变（stop_gained mutation）可破坏其亚细胞定位。多组学分析显示，ubp5突变在全局水平上影响玉米籽粒发育过程中的转录组、蛋白质组与泛素化组。通过蛋白质相互作用与降解实验，我们证实ZmUBP5可与ZmEMB140相互作用，并可能调控其泛素化水平。ZmEMB140被注释为一种对剪接过程至关重要的剪接体相关蛋白。携带ZmEMB140中c.652C>T|p.Q218*终止密码子获得型突变的玉米突变体，其籽粒尺寸更小，胚胎与胚乳均发育不全。此外，我们证实ZmEMB140通过影响可变剪接参与前体mRNA（pre-mRNA）加工过程。ZmEMB140可与4种U6小核RNA相关Sm样蛋白（U6 snRNA-associated Sm-like proteins, LSM）以及2种前体mRNA加工因子（pre-mRNA processing factors, PRP）发生相互作用。本研究首次揭示了去泛素化酶ZmUBP5参与调控玉米籽粒发育的分子机制。