A Preliminary Study On The Molecular Mutational Mechanism Of Genic Male-sterile Rice Dwarfing Mutants

Since the rice dwarfing breedings made the output of the rice increase breakthroughly, the research workers pay attention to the hereditary research of the dwarfness, exploration and qualification of new dwarf-ancestors. Our group succeeded in obtaining the dwarfing mutants SV1S and SV14S from the rice variety Zhu-1S with the technique of somaclonal variation. The result indicate that SV1S and SV14S are dwarfing Thermo-Sensitive genic male sterile line. They could inherit stably and obviously in reducing the height of plants, had the ability to resist lodging and obvious superiority in combining ability. They are new-type variety might be spreaded widely in rice production. But there was lack of research to the mutational mechanism of the dwarfing rice. The molecular mutational mechanism of the dwarfing mutants remained unknown. So Zhu-1S and the dwarfing mutants SV1S and SV14S were analysed, to carry out preliminary studying on the molecular mechanism of dwarfing mutant, and the main results were described as follows: 1, Sensitivity to exogenous GA(gibberellion) of Zhu-1S ,SV1S and SV14S Zhu-1S and the dwarfing mutants SV1S and SV14S were used as the plant materials, we analyzed the response of endosperm,the second leaf sheath and internodes to exogenous GA3. The results showed that the endosperm of Zhu-1S was more sensitive to exogenous GA3 than those of SV1S and SV14S; Their second leaf sheaths of three kinds of rice materials didn't extend obviously when in the range of 10-10mol/L to 10-9mol/L, But the elongation of second leaf sheaths was obvious when the concentration of GA3 was above 10-9mol/L. The lengths of their second leafs were from 3.5cm to 4.0cm at their maximum when the concentration of GA3 was 10-5mol/L. It showed that their second leaf sheaths were all sensitive to exogenous GA3; during certain concentration, GA3 could heighten their internodes obviously, length of their internodes were all sensitive to exogenous GA3.But the position effected by GA3 and the concentration sensitive to GA3 were different. Exogenous GA3 effected the height of Zhu-1S by the second and third internodes compared with SV1S and SV14S by their three internodes. The concentration of GA3 that Zhu-1S was sensitive to was from 10-4mol/L to 10-3mol/L compared with SV1S and SV14S in the rang of 10-4mol/L. The results showed that SV1S and SV14S were dwarfing mutants sensitive to GA3. 2, Analysis of the dwarfing mutant at DNA molecular level The diversities of Zhu-1S, SV1S and SV14S at the total DNA and mtDNA level were analysed respectively by RAPD molecular markers. A total of sixty arbitrary ten-mer oligonucleotide primers were screened with the genomic DNA of the three rice lines (Zhu1-S, SV1S, SV14S). Twelve primers produced thirty-three polymorphism fragments, Three of them produced six obviously repeatable polymorphic markers among rice lines tested. These results indicate it is different in genomic DNA between rice variety Zhu-1S and its dwarfing mutant SV1S and SV14S. Using these RAPD markers, the three rice lines can be effectively identified, and the genetic relationship among them can be shown; because the dwarfing mutant SV1S and SV14S were produced from rice variety Zhu-1S with the technique of Somaclonal Variation. It was reported that the cytoplasm DNA might mutate during culturing, so we analysis the diversity of Zhu-1S, SV1S and SV14S at the mtDNA level by RAPD molecular markers. The mtDNA from these materials were screened primarily by sixty random sequence primers. Ten polymorphic fragments different between the three materials were produced by the primers S43, S48 and S60 of the sixty primers, these results indicate it is different in mtDNA between rice variety Zhu-1S and its dwarfing mutant SV1S and SV14S, which showed somaclonal variation could induced wide-rang of mutation not only in the rice genome but also at the mtDNA level. What concrete connection of variation at the DNA level above-mentioned with the dwarfing character are being studied further by our group.