1a.Objectives (from AD-416)
1) Correlate metabolites during seed development with final seed composition; and. 2)Explore the basis for variation in seed composition as a function of canopy position.
1b.Approach (from AD-416)
The proposed studies will focus on three broad aims. First, we will build on our observation that the free pool of amino acids (in particular asparagine) during development is correlated positively with seed protein content at maturity. Free amino acids will be extracted from rapidly growing seeds and quantitated using GC-MS. We will attempt to identify quantitative trait loci associated with the free asparagine pool in developing seeds of a segregating inbred population that has previously been genotyped. Concurrent studies will examine the levels of enzymes involved in asparagine metabolism (asparaginase and asparagine synthetase) using custom anti-peptide antibodies for immunoblotting analysis. Second, we will initiate a new effort to identify soybean genotypes containing high levels of sulfur amino acids (methionine and cysteine) in mature seeds. If preliminary findings can be confirmed, appropriate crosses will be made to begin to move the high-sulfur trait into enhanced germplasm lines. Third, we will continue to examine the effect of canopy position on seed composition. In general, seeds that develop at the top of the canopy have more protein, less oil, and fatty acids contain more monounsaturated oleic (18:1), compared to seeds at the bottom of the canopy. Our current results suggest that quantitative differences exist among genotypes in these responses. In the proposed studies, we will determine whether these canopy position effects may simply reflect sensitivity to environmental parameters within the canopy and concurrently, appropriate crosses will be made to identify controlling genes.
The overall goal of this research is to identify physiological determinants that control or impact seed composition. One specific project is focused on the variation in seed composition as influenced by canopy position. We have observed that seed produced at the top of the canopy tend to be higher in protein and lower in oil. In addition, the fatty acid composition of the oil is also affected with seed from the top of the canopy having higher content of oleic acid (18:1). Analyses are currently underway to examine a large data set collected from plants growing at multiple locations and over several years to determine whether the canopy effect is genetically controlled. Collectively, these studies may help to develop soybean cultivars with increased seed protein content and greater compositional stability. This work relates to NP302 Component 2C: Develop high-value products.