2012 Annual Report
1a.Objectives (from AD-416):
To elucidate regulatory mechanisms of genes that control saturated fatty acid
composition in sobyean seed; to characterize the mechanisms that control phytate
content in seeds, and the impact of low phytate on seed viability and soy meal
digestibility; to identify genes and gene products that cause immune responses to
soybean and devise ways to mitigate these reactions.
1b.Approach (from AD-416):
Evaluate metabolite levels and expression of genes encoding enzymes of the phytate biosynthetic pathway of low and normal phytate seeds in response to increasing P supply; Evaluate amino acid substitution in desaturase genes; Evaluate differences in the amount of allergens bound to soy protein, determine their location in the protein, and assess variation in their structure. BSL-1. 10/01/06.
The stability of seed set and seed composition for two conventional (20-30% oleic acid) and six mid-oleic (50-60% oleic acid) soybean genotypes was investigated using growth chambers set for 12 or 9 hour day lengths. Under short day (9 h) conditions, pod number and seed number at maturity declined significantly compared to a 12 h day for both conventional and mid-oleic genotypes.
A bulk seed increase of low phytate soybean lines was completed. Poultry feeding experiments with low phytate and conventional phytate soybean were begun and preliminary data are being analyzed.
Protein blot analyses clearly indicate that sera from dogs, pigs, rabbits and fish have antibodies against multiple proteins other than the seed storage proteins. We are collaborating with ARS-SRCC, New Orleans to determine if proteins bound to antibodies against the soy proteins can be identified directly by mass spectrometry. In brief, rabbit antibodies against non seed-storage proteins are enriched and attached to a magnetic bead. The antibody-bead complex is used to purify the antigenic soy proteins and the bound proteins identified using mass spectrometry. If this approach is unsuccessful standard two-dimensional gels electrophoresis can be employed.
Carbohydrates associated with antinutritional factors (raffinose, stachyose and phytate) and taste components (monosaccharides, sucrose and starch) were measured in seeds of 1500 soybean mutants. Phytate was also indirectly measured by determining the level of free phosphate. Mutants with increased starch and/or sucrose and decreased levels of antinutritional factors were identified. Some lines planted in the winter nursery were lost because they shattered and were replanted this summer. One interesting line appears to have reduced levels of phytate, raffinose and stachyose.
Mutagenesis of soybean resulted in potentially valuable changes in seed soluble carbohydrate and starch levels. Soybean varieties with high starch, low phytate, and high sugar content are provide better taste and nutrition and are desired by the human and animal food industry. ARS researchers at Raleigh, NC confirmed that 2 lines were high in starch, 4 were lines low in phytate, and 4 lines had high sucrose to raffinose ratios after a second year of testing. The performance of these lines is being evaluated in the field this year and crosses are being made with elite lines.
Day length used to probe stability of the M23 mid-oleic soybean. M23 is an X-ray mutant line with a mid-oleic acid phenotype that has been used in breeding to improve oleic acid content. ARS researchers at Raleigh, NC compared the phenotypic responses of M23 with those of conventional and non mutagenized mid-oleic genotypes to short day length manipulation and found additional characteristics unique to M23. Short day (9 hour) responses for M23 include significantly decreased protein content, significantly increased oil and oleate content, in addition to delayed senescence and the production of many pod primordia which fail to develop.