Allele Specific Gene Regulation in Maize Floral Organs

玉米P基因编码一个myb同源转录调控因子，调控玉米花器官中类黄酮色素合成的三个基因。P-rr等位基因决定果皮和穗轴颖片的色素沉着，而P-wr等位基因只决定穗轴颖片的色素沉着，而不决定果皮的色素沉着。导致P-wr等位基因器官特异性表达的机制将被研究。虽然果皮是无色的，穗轴的颖片是红色的，但两种组织都含有P-wr转录本。还确定了这两个等位基因编码的蛋白质在Myb DNA结合域外的两个位置以及在c端的截断和替换上存在差异。基于粒子枪的瞬态分析系统将用于确定P-wr蛋白的哪些变化负责器官特异性表达。除了瞬时检测外，还将通过在转基因植物中表达P-wr cDNA来研究P-wr等位基因在体内的表达模式。已经发现P-wr位点包含一个由大约5个拷贝的12.6 kb DNA序列组成的重复DNA，该位点的基因组组织将进一步研究。功能的P-wr基因将通过使用Ds插入来鉴定。将对另外两个P基因等位基因的cDNA克隆进行测序，并研究它们对P-wr表达的反式修饰剂UFO的响应性。这一研究结果将有助于阐明植物发育过程中产生特定基因表达模式的基本调控机制。＊＊＊

9601285 Peterson The maize P gene encodes a Myb-homologous transcriptional regulator of three genes for flavonoid pigment biosynthesis in certain maize floral organs. The P-rr allele specifies pigmentation of both the kernel pericarp and cob glumes, while the P-wr allele pigments the cob glumes but not the kernel pericarps. The mechanism(s) leading to organ-specific expression of the P-wr allele will be investigated. It has been found that both tissues contain P-wr transcripts although the pericarps are colorless and the cob glumes are red. It has also been determined that the proteins encoded by these two alleles differ at two positions outside the Myb DNA binding domain and by a truncation and replacement at the C-terminus. A particle-gun based transient assay system will be used to determine which changes in the P-wr protein are responsible for organ-specific expression. In addition to transient assays the in vivo expression pattern of the P-wr allele will be studied by expressing the P-wr cDNA in transgenic plants. It has been found that the P-wr locus contains a repetitive DNA consisting of approximately 5 copies of a 12.6 kb DNA sequence and the genomic organization of the locus will be further investigated. The functional P-wr gene will be identified by the use of a Ds insertion. cDNA clones from two additional P gene alleles will be sequenced and their responsiveness to UFO, a trans-modifier of P-wr expression, will be studied. %%% The results of this study will help to elucidate fundamental regulatory mechanisms which produce specific patterns of gene expression during plant development. ***