Genetic Analysis On A Long Sterile Lemma Gene In Rice

Rice(Oryza sativa L.) is one of the most important food crops in the world, and it is the model plant for studying the molecular genetic mechanism of plant development in monocot. The mechanism of floral organ specification is always a hot topic in plant molecular biology, by contrast, mechanism that regulate the development of organs to monocot crops remain unclear. The appearance of long sterile lemma rice is important for studying mechanism under sterile lemma development of rice, uncover the interaction between different genes involved in flower development, and this is also a significant contribution to perfect and reinforce the flower organ development model of monocotyledon.We found a long sterile lemma rice in the materials imported from the United States, and temporarily named as Y93. In this study, we investigated it’s morphology of the floral organs and agronomic traits. Meanwhile, genetic analysis and gene mapping of the long sterile lemma gene were conducted. The main results were followed as bellows:1. Morphology and agronomic traits of Y93. In a natural growing condition in Nanjing, the height of Y93 was about 1.4 meter. The plant type was loose, leaves were long curved, stem was slender and prone to lodging, and its main traits were inclined to indica rice variety. The length of sterile lemma in Y93 was significantly greater than the length of lemma, showed a phenotype of lemma coated with sterile lemma. After removing the lemma/petal of Y93 and 9311, it was found that there is no significant difference among the other floral organs in addition to the sterile lemma. Based on the analysis results of agronomic traits, it was found that the length of sterile lemma of Y93 was significantly greater than in 9311. In addition, the brown of Y93 was lower than 9311.2. Genetic analysis of the long sterile lemma. In this study, F1 and F2 population which generated from Y93×9311, were studied in order to determine the genetic model of long sterile lemma gene. Both F1 plants of Y93×9311 and 9311×Y93 showed normal length of sterile lemma (as variety 9311). However, the F2 population showed remarkable segregation. A total of 1065 F2 plants was observed, and there were 262 plants showed long sterile lemma, and the others showed normal. Therefore, the separation ratio of long sterile lemma plants to normal plants was 1:3.06. The χ2 test for F2 population indicated that it is agreed to Mendel separation ratio of 1:3. All these results showed that the long sterile lemma was controlled by a single recessive gene, and temporary named lsl (long sterile lemma).3. The mapping of lsl gene.262 recessive plants of F2 population which was constructed from a cross of Y93×9311 were used as gene mapping population. Using map-based cloning method and SSR molecular markers, the lsl gene was mapped on the short arm of Chromosome 7 between RM5344 and RM3225, and the genetic distance was 0.38 cM and 2.10 cM, respectively.4. The position of lsl gene on rice genome was substantially the same with G1 gene which has been reported previously. According to the full-length DNA sequence of G1, we designed two primers, and used the DNA of Y93 and 9311 as template to amplify and sequence. Sequence analysis showed that the sequence of 9311 was exactly the same with G1 gene, and that of Y93 showed two sense point mutations. Counting from the start codon ATG, a T to G transition at nucleotide position 569 lead to methionine translation into arginine. Deletion of the G in the nucleotide position 584 resulted in an amino acid expression change and a premature termination of transcription. The result indicated that lsl gene is a new allelic of G1 gene.