1a. Objectives (from AD-416):
1) Identify genetic loci which contribute positive alleles to seed yield and quality traits and which control variation in seed quality, especially seed oil, protein, carbohydrate content, and fatty acid composition of legume seeds; develop strategies to facilitate effective transfer of useful genes into cultivated legumes; 1a) Mapping and characterizing mutant alleles that contribute to variation in seed fatty acid composition; 1b) Discovery of the molecular identity of genes that influence overall protein or oil content by forward genetics approaches. 2) Determine epigenetic patterns in soybean seeds during development, assess relationships between chromatin state and gene expression, and develop approaches to modify gene expression in developing seeds; 2a) Genome-wide profiling of epigenetic state and gene expression in developing soybean seeds by chromatin immunoprecipitation followed by sequencing (ChIP-seq) and RNA sequence-based expression profiling (RNA-seq).
1b. Approach (from AD-416):
The project uses molecular biological approaches to study the regulation of genes that are required for soybean seed development. Biochemical approaches are used to study the interactions and function of gene products that are important for the accumulation of storage proteins or fatty acids in seeds. Molecular and genetic tools are used to define genes and genetic intervals that contribute to seed protein and oil content in mutant plants.
3. Progress Report:
We are working with a number of soybean lines with altered fatty acid composition to characterize the genes involved in seed composition as well as to evaluate the effects of combination of mutant alleles to stack composition traits. We have identified 6 mutations in the SACPD-C gene and verified that these mutations are related to increased levels of stearic acid in soybean seeds. These mutations confer an increased level of stearic acid in the seed which will make soybean oil more useful in cooking fats. Another goal for the improvement of soybean oil is to increase the levels of oleic acid to increase the stability of the oil. During this project period we continued to characterize soybean fatty acid mutants with increased levels of oleic acid, identifying 7 lines carrying new mutations in known genes that result in high levels of oleic acid, and range in oleic acid content from 33-46%. These mutations may be combined to result in even higher levels of oleic acid and prove to be a useful resource for soybean breeders and geneticists. To identify novel mutations, we have expanded our efforts to generate both conventional and next-generation genetic mapping populations to identify the genes responsible for several other fatty acid traits, including alterations in linolenic acid, palmitic acid, and stearic acid. One milestone this year was to use the bulk segregant resequencing technique to identify genes responsible for altered fatty acid content. This technique uses next-generation sequencing on individuals from a segregating population that share a fatty acid phenotype to quickly identify linked genes. This growing season we have obtained the tissue and will finish the phenotyping of an additional generation to ensure that the lines that will be used for sequencing are true-breeding. We have initiated a new project to identify the transcriptional regulators bound to the promoters of seed storage protein genes during seed development, seed samples have been collected that will be analyzed in the fall.