Determination Of β-glucan Content And CSLH Gene Cloning Among Avena Species

The genus Avena L. belonging to Aveneae. Pooideae, Gramineae, including about 29 species, six genome constitutions (A, C, AB, AC, CC and AACCDD). Oat is an important crop with higher nutrition and economic value, and usually used for food and feed. Oat β-glucan has important function in reducing the cholesterol, low-density lipid, preventing and treating diabetes and cardiovascular disease. Germplasms with low β-glucan is often used as feed, while high β-glucan germplasms available for health food and medicine development. However, oat p-glucan content around the world is unclear at present. In order to take advantage of oat β-glucan, we measured the β-glucan content of 112 oat germplasms, and cloned CSLH gene which encoding oat β-glucan synthesis. We made phylogenetic analysis of all gene sequences obtained to understand the origin and evolution of Avena species, then clarify the classification of individual species. The main results are as follows:1. We used mixed-linkage beta-glucan assay procedure(EBC Methods 3.11.1) to measure the β-glucan content of 112 oat populations all over the world. Results showed that β-glucan content was significant difference between populations, the minimum content was 1.15%, the highest level reached 8.37%, all materials had average content of 4.31%. Only three populations had β-glucan content more than 7%, they were CN25849, CN25859, CN25897. Only population PI258663 and CN21405 had β-glucan content less than 2%. In this study, species A. atlantica, A. barbata and A. sterilis has β-glucan content more than 5.7%, species A. sativa and A. ventricosa has P-glucan content less than 2%. Of all materials tested, species with extreme β-glucan content was present in diploids. As diploid has the highest average level, and Cv diploid has the lowest average level. These species or populations can be used to develop high β-glucan content products or low β-glucan forage species.2. We obtained 334 CSLH gene sequences in total, and 86 most representative sequences were selected to make phylogenetic analysis. Remarkable difference exists in different oats species, populations or copies. There was one copy type in diploids, more than two kinds of copy type in polyploid species. We selected 10 populations with high β-glucan and 10 populations with low β-glucan, translated their exon into amino acid, then did sequence alignment and build phylogenetic tree. Results showed that different populations had 350-353 amino acids, populations with high or low β-glucan content were different in DNA (435bp) and amino acid (145aa). The amino acid of high β-glucan materials were "VLLARA", while low β-glucan materials were "VL-ARP". We may clone this different fragment for β-glucan molecular breeding.3. In order to make clear of the relationships between diploid species, all diploid sequences were used to phylogenetic analysis. Results showed that As diploid populations scattered in different branches, while others A populations stayed in a single branch, indicating that As genome was the fastest evolution type among all A diploids. This situation also made it difficult to judge the relationships of A diploids. All C diploid populations interleaved together, indicating that they had close relationship each other.4. In order to make clear of the origin and evolution among polyploid species of Avena, we build different phylogenetic trees. Results showed that tetraploid AB species A. agadiriana clustered into a separate branch, separating from the other three AB tetraploids, indicating that A. agadiriana was different from the other AABB tetraploids. Different hexaploid species stayed together with different A genome diploids, such as A. sativa with A. hirtula and A. wiestii, A. fatua with A. damascena, A.sativa ssp.nuda with A. strigosa, indicating that different diploids all might be the A genome source of hexaploids. Each C diploids was likely to be the C donor of polyploid species. The clustering analysis of all genomes indicated that there was a sub-branch contained A. agadiriana, AC genome tetraploids A. insularis, A. murphyi, A. maroccana, and several hexaploids. Combining conclusions of previous studies, we speculated that this branch was the D genome source of polyploids, but this hypothesis needed more evidence to confirm.