Fine Mapping Of The Maize Dwarf Gene Dt And The Pilot Study About Its Dwarfing Mechanism

At present, 25 dwarf genes had been identified, but most of them had kind of bad inherit linkage therefore restricting their use in maize breeding. So it is important to develop and identify a new source of dwarf gene to broaden the genetics basis of maize breeding. Dwarf mutants in plant are crucial for elucidating regulating mechanisms for plant hormone synthesis and signal transduction development. So it is important to develop and identify a new source of dwarf gene for investigators.Maize dwarf mutant 52333Dt was bred by Shandong Agricultural University. The dwarfing trait was controlled by a new single dominant gene, which was temporarily named Dt. Dt gene was located between 199151-1 and 216865-6 by P11/52333Dt//P11, and the physical distance was about 1 Mb between them. Based on previous study, the article carried on preliminary research on the dwarfing mechanism, and fine mapping of Dt gene. The results were as follows:1. Dwarfing mechanism of maize dwarf mutant 52333DtIn segregation population, the plant height of dwarf individuals was only 49.57 % of high individuals, and dwarf individuals had one more internodes compared with high individuals on average, were shortened equally. Cytological observation revealed that the internodes were shortened because the cells stretch in dwarf individuals stem were inhibited. There were no obvious difference of endogenous hormones GA,ZR,ABA content in near-isogenic lines. However, the difference of IAA content was notable. We deduced IAA relates to dwarfing mechanism.2. Fine mapping of Dt gene(1) Based on previous mapping, we built B73/52333Dt//B73 and Mo17/52333^Dt//Mo17 for fine mapping. Genetic linkage analysis showed that physical map of ctg415 was conversed. In practice, the physical distance between 199151-1 and 216865-6 was about 4Mb.(2) We used 147 pairs SSR markers for fine mapping. ^Dt gene was located between 207675-5 and 200041-1 by B73/52333^Dt//B73, and the physical distance was about 1.2 Mb between them. ^Dt gene was located between 1941137 and 199382-1 by Mo17/52333^Dt//Mo17, and the physical distance was about 1.2 Mb between them. ^Dt gene was located between 187790-4 and 199382-1 by P11/52333^Dt//P11, and the physical distance was about 400 Kb between them. The mapping location by P11/52333^Dt//P11 was minimal, and in the locations by B73/52333^Dt//B73 and Mo17/52333^Dt//Mo17.(3) Combination the size of three populations and SSR mapping situation, we used 3500 BC₁ individuals of P11/52333^Dt//P11 for fine mapping. We successfully developed CAPS markers C196159-7 and C187790-15. ^Dt gene was finally mapped between markers 187790-4 and C187790-15, in one genomic sequencing BAC (AC187790). The genetic distance from 187790-4 was 0.06 cM, and the genetic distance from C187790-15 was 0.14 cM. The physical distance between 187790-4 and C187790-15 was about 100 Kb. It was a solid foundation for cloning the dwarf gene and studying its functions.