The maize imprinted gene floury3 encodes a PLATZ protein required for tRNAs and 5S rRNA transcription through interaction with RNA polymerase Ⅲ

【摘要】：Maize floury3(fl3) is a classic semi-dominant negative mutant that exhibits severe defects in endosperm but appears normal in the plant.The mutant phenotype only occurs when fl3 is transmitted through the female.We cloned the fl3 gene and determined that it encodes a PLATZ(PLant-specific AT-rich and Zinc-bind) protein.FI3 is specifically expressed in starchy endosperm cells.It revealed that//3 results from a point mutation,which results in an Asn to His replacement in the PLATZ domain.Protein sequence alignment of FI3 alleles from 165 inbred lines and its orthologues from other species demonstrated that the Asn residue is extremely conserved,indicating that this amino acid is critical for FI3's function.Transformation of fl3 in maize and rice reproduced the same floury phenotype in seeds,confirming the cloned gene being FI3.We also investigated the expression levels of the FI3 and fl3 alleles and their methylation status in their reciprocal crosses and found this gene is subject to imprinting,which leads to a suppressed expression of fl3 when transmitted from the male,which may partially explain its semi-dominant behavior in the genetic analysis.Yeast two-hybrid screening and then BiFC and Co-IP revealed that FL3 protein interacts with RPC53 and TFC1,two critical components of the RNA polymerase Ⅲtranscription complex.In fl3,the levels of many of tRNAs and 5 S rRNA transcribed by RNA polymerase III are significantly reduced,suggesting that the incorrect f13 protein may affect their biogenesis.The transcriptome was dramatically altered in//3,in which the differentially expressed genes are primarily enriched in pathways related to translation,ribosome,misfolded protein responses and nutrient reservoir activity.As a consequence,these changes may lead to defects in endosperm development and storage reserve filling in fl3.

【作者单位】：National Key Laboratory of Plant Molecular Genetics,CAS Center for Excellence in Molecular Plant Sciences,Institute of Plant Physiology & Ecology,Shanghai Institutes for Biological Sciences,Chinese Academy of Sciences Institute of Biotechnology and Nuclear Technology,Sichuan Academy of Agricultural Science College of Agronomy,Shenyang Agricultural University
【分类号】：Q943.2;S513