Studies On Cloning And Expression Of Gibberellin Biosynthesis Related Genes In Wheat

Gibberellin (GA) is an important plant hormone which regulates plant growth and development, including seed germination, stem elongation, leaf expansion, flower and seed development, and root growth. As a result, GAs has great potential in yield and status improvement of crop. Genes encoding the enzymes involved in GA synthesis and metabolism have been cloned and studied in several higher plants, but there are very few reports about this in wheat. In order to investigate the mechanism of GA biosynthesis and metabolism in common wheat (T. aestivum), the GA metabolism related genes (GA3ox1and GA3ox2) were cloned using homology cloning in wheat Ning98-2105and Chinese Spring, and their expression patterns were also analyzed in the paper. The main results are as follows:1. The GA3oxl gene, which is1456bp in full length, was cloned from Chinese Spring (CS), Ning98-2105(containing the dwarf gene Rhtl2),Triticum urartu and Aegilops tauschii. The identity among these GA3oxl genes was found to be more than98%. In Aegilops speltoides, however, the GA3oxl gene is1467bp and the identity among these five GA3oxl genes is more than94%. According to the results of bioinformatic analysis, these GA3oxl genes have three exons and two introns. The sizes of the two introns are80bp and81bp respectively. And the ORF of all five GA3oxl genes is1149bp which encodes a protein with382amino acids.2. The sequences of the three types of GA3ox2gene which are about1800bp in full length were amplified using Ning98-2105(containing dwarf gene Rht12) as materials, named as GA3ox2-1, GA3ox2-2and GA3ox2-3respectively.The full cDNA sequences of GA3ox2genes are about1400bp.These genes contain two introns and have consistent length of sequence and high similarity.The identity between the three GA3ox2 gene sequences isolated from Ning98-2105and Chinese Spring Wheat is93%.The similarity among these three GA3ox2genes themselves is more than99%.3. The GA20oxl gene which is about1200bp in full length was cloned from Chinese Spring (CS) and Ning98-2105(containing the dwarf gene Rht12).The identity between the GA20oxl genes isolated from Ning98-2105and Chinese Spring Wheat is99%.The similarity among three GA3ox2genes themselves is91%to94%.4. It is found that the3copies of TaGA3ox2are localized on the chromosomes3A,3D and3B respectively, and the3copies of TaGA20ox1are localized on the chromosomes4A,5B and5D respectively.5. Real Time-PCR analysis shows that GA3oxl gene gene has the highest expression levels in the uppermost node of Ning98-2105(containing the dwarf gene Rhtl2). It is indicated that GA3oxl may function in wheat node and reduce the length of node in dwarf cultivars. GA3ox2has similar function to GA3ox1in node length regulation. It is interesting that the expression level of GA3ox2in young spike of Ning98-2105is higher than that of the ordinary wheat, which indicates that GA3ox2also has a role in growth regulation of young spike. The expression level of GA20ox1gene was found to be the highest one in the second internode from the panicle of Ning98-2105, which suggests that GA20oxl plays a key role in reducing the length of internode of wheat. In addition, GA20ox2gene has similar roles in internode growth regulation.