Gene Mapping And Expression Analysis On A Ultra-Dwarf Mutant In Upland Cotton

Dwarf plant resources are few in upland cotton.A ultra-dwarf mutant, as a new mutant inheritance has been previously studied by our item group, which indicated that the mutant was controlled by single recessive gene, of inheritance in a simple mode, to be proved a gibberellin synthesis-deficient mutant. In this paper, the ultra-dwarf mutant were researched in several aspects as follows.1. Seventy pairs polymorphic primers were picked out from1350primers, covering all the identified chromosomes by screened in parents and near-isogenic lines. Then mapped with F2population, from intraspecific crosses of "ultra-dwarf1" and "Xinluzao16", by bulked segregation analysis. Linkage analysis and molecular linkage map of ultra-dwarf mutant gene du was constructed by Join Map4.0. Thirty-six primers were linked to eight linked groups, and du was linked to LG01. Seven co-dominant markers linked to du were NAU2679、NAU2749、NAU905、NAU2838、NAU5373、NAU2238and NAU4946. Based on the known genetic map of tetraploid cotton,markers NAU4946、NAU2238、NAU905、 NAU5373and NAU2679were on the chromosome6, and the target gene du was located between NAU2238and NAU4946, their genetic distance were3.5cM and1.5cM, respectively. Hence, the du gene was located on the chromosome6.2."Ultra-dwarf1" is a gibberellin synthesis-deficient mutant. Used "Ultra-dwarf1"and its wild-type as materials, analyzed their expressions of the key enzyme gene related to GA biosynthesis by real-time fluorescent quantitative PCR. The results showed that occurrence of the ultra-dwarf mutant was closely related to the down-regulated expression of three key enzymes genes:ent-kaurene oxidase, copatyl diphosphate synthase and ent-kaurenoic acid oxidase. The amount of gene expression of the mutant was only10.4%-.26.3%and25.3%compared with wild-type.3. The down-regulated expression of ent-kaurene oxidase gene was the most obviously, its cDNA fragments was sequenced, then got a sequence with a size of79bp. As a query probe, compared with the sequence of mRNA in other crops by tblastx, the result showed that the sequence has high homologous to the mRNA sequence of the ent-kaurene oxidase related to GA biosynthesis. The similar amino acid sequences including of Ricinus communis, Castanea mollissima, Populus trichocarpa, ZEA, Lactuca sativa, Oryza sativa, Stevia rebaudiana, Cucurbita maxima, Momordica charantia, Coffea, Fragaria and Arabidopsis thaliana were compared to the amino acid sequence of the original EST sequences (DT574281). The results indicated that the primers to be designed by this sequence was in conserved domains, indirectly proved that the reasonable of the designed primers. The result established a foundation for cloning full length of the key enzyme gene in the cotton.