Highly comparative genetic analysis for genes located on terminal region of chromosome 4 among several wild species of rice

根状茎是野生稻品种的特征之一。对水稻品种C105204的F2分离分析表明，根茎化性状由4号染色体上的显性基因控制。进一步发现该基因与lg基因有连锁。基于与玉米Lg1的同源性，通过pcr分析，揭示了位于4号染色体上控制舌状叶的ligulless基因（Lg）的基因组序列。Lg基因有414个氨基酸组成的多肽，由3个外显子组成。对部分无舌突变体的Lg基因3635bp进行了基因组序列分析。发现T-65和具有T-65遗传背景的lg近等基因系t - 65lg具有相同的序列。而用NaN3诱导的YH - lg在第1内含子和第2外显子之间的剪接位点发生了单碱基置换G到A，在第2内含子的TC重复序列中加入了1组TC。用EMS诱导的短舌形突变体85ACC152 ln -a在第一个外显子和第一个内含子之间的剪接位点上也发生了单碱基替换，从T到C。虽然YH lg和85ACC152 lg-a在正常mRNA所需的剪接位点发生了非常重要的改变，但T-65 lg的lg基因组序列与T-65没有任何差异。结果表明，T-65 Lg基因上游5′区序列可能与T-65不同。我们从Pl^w植物叶片cDNA文库中分离到两个cDNA OSB1和OSB2，它们与玉米R基因家族中的基本螺旋-环-螺旋（bHLH）蛋白具有显著的同源性。利用F2群体的RFLP分析表明，这两个基因与紫叶表型共分离。短暂互补实验表明，OSB1和OSB2可诱导花青素途径。这些结果表明，Pl^w等位基因可能是复杂的，由至少两个编码bHLH蛋白的基因组成。

Rhizomes of Oryza longistaminata is one of the characteristics of wild species of rice. Analysis of F2 segregation between C105204 (an IRRI's accession of O. longistaminata) and a rice cultivar showed that rhizomatous trait was controlled by a dominant gene on vhromosome 4. Further, this gene was found to be linked with lg gene.Genomic sequence of Liguless gene (Lg) located on chromosome 4, which controls ligule was revealed through PCR-based analysis based on the syntenic homology to maize Lg1. Lg gene has a polypeptide of 414 amino acids and Lg gene is composed of 3 exons.Gernomic sequences, 3635 bp of Lg gene of some liguleless mutants were analyzed. T-65 and a near isogenic line for lg with T-65's genetic background, designated T-65 lg were found to have the same sequence. However, YH lg, which was induced with NaN3 had the single base substitution, G to A, at the splice site between first intron and second exon and add one set of TC in TC repeat at second intron. Short ligule mutant, designated 85ACC152 lg-a, which was induced with EMS also had single base substitution, T to C, at the splice site between first exon and first intron. Although YH lg and 85ACC152 lg-a had very important alteration at splice site required for normal mRNA, T-65 lg which is liguless had any differences of Lg genomic sequence from T-65. This results suggested that sequence of upstream region at 5' of Lg gene in T-65 lg might be different from that of T-65.We isolated two cDNAs, OSB1 and OSB2, from cDNA library of Pl^w plant leaves, showing significant identity to the basic helix-loop-helix (bHLH) proteins found in the maize R gene family. RFLP analyses using an F2 population indicate that both genes co-segregate with the purple leaf phenotype. A transient complementation assay showed that the anthocyanin pathway is inducible by OSB1 or OSB2. These results suggest that the Pl^w allele may be complex and composed of at least two genes encoding bHLH proteins.