Identifies Differential Gene Expression Related To Gravitropism-Horizontal Gravitropism In Creeping Shoots Of Ground-Cover Chrysanthemum

Ground-cover chrysanthemum, a new variety population, is especially fitted for beautifying garden, including two types of low and creeping architecture. The recently developed creeping type is well accepted as a ground-cover garden species, thanks to its stolons similar to those of the strawberry. As many environmental factors, such as light, temperature, moisture, nutrient conditions and other biological which affect plant growth, the gravity is one of the most important environmental factors which determined the form of higher plants. Abundant studies showed that the shoot growth directions are regulated by illumination and gravity. Many mutants with creeping habit have been identified to be related to loss or reduced gravitropism. But now there is little investigation to discover the creeping mechanism of the creeping ground-cover chrysanthemum. The gene library of the curve part of creeping shoots was constructed using molecular biology methods, the gene expression characteristics of the curve part of creeping shoots was analysis. The target gene was cloned and make through expression analysis to reveal the molecular mechanism of the formation of creeping shoots. The main results showed as below:(1) In this study, the bending stems were cut into the upper and lower halves (upper stem segment half, USSH; lower stem segment half, LSSH) by bisection with a razor blade, and two library were constructed. Sequencing of 43 selected clones produced 41 unigenes (40 singletons and 1 unigenes), which were classifiable into 9 functional categories. By BlASTn, BlASTx, COG analysis software such as biological sequence of positive clones and analysis of biological information processing can be divided into 41 gene families (22 of which came from the upper side,19 from the lower side), nucleoside acid sequence on the NCBI accession number FS999558-FS999598. A notable frequency of genes involve in cell wall biosynthesis were found regulate by gravistimulation. ESTs similar to cell-wall-protein genes, such as beta tubulin (TUB), subtilisin-like protease (SBT), glutathione S-transferase (GSTs), and expensing-like protein (EXL), lipid transfer proteins (LTPs), glycine-rich protein (GRP) and membrane proteins, which might participate in primary cell wall or secondary cell wall construction and modification, were up-regulated during gravistimulation in the upper side or lower side. Our findings also highlighted the function of some metal transporter during asymmetric growth, including the boron transporter and ZIP transporter, which were thought to be primarily for maintaining the integrity of cell walls and played important roles in cellulose biosynthesis.(2) Aβ-tubulin gene named CmTUB was successfully cloned from chrysanthemum 'Yuhuajinhua'by RT-PCR and RACE technology, the gene accession number is AB608732. Sequence analysis showed that cDNA full length of chrysanthemum 'Yuhuajinhua'CmTUB gene is 1544bp, encoding 446 amino acids, which consists of 198 amino acid residues of the GTPase domain and 138 amino acid residues of the C-terminal component and includes six connection with tubulin domain-related. Phylogenetic analysis showed that cotton and other dicots have closer relationship with chrysanthemum 'Yuhuajinhua'CmTUB gene. Quantitative PCR analysis showed that CmTUB gene is constitutively expressed genes, gravity can inhibit the expression of CmTUB in the upper side; NAA and CaCl2 can promote the expression of CmTUB in the coated side; TIBA and EGTA can inhibit the expression of CmTUB in the coated side.