**51. Polysaccharides**

**47. Vestitonereductase and chalconereductase**

flowers, leaves, stems, and roots [51].

**49. 5'-adenylylsulfate reductase**

**50. Soybean ATP sulfurylase**

plant metabolism [52].

Relationships

254

tion pathway [53].

The complete mRNA sequences of two soybean genes-vestitone reductase and chalcone re‐ ductase, were amplified using the rapid amplification of cDNA ends methods. Soybean ves‐ titone reductase gene encodes a 327 amino-acid protein with pronounced resemblance to *Medicago sativa* vestitone reductase. The soybean chalcone reductase gene encodes a 314 ami‐ no-acid protein highly homologous to the kudzu vine and medicago sativa chalcone reduc‐ tases. The two genes were differentially expressed in soybean embryos and endosperm,

A Comprehensive Survey of International Soybean Research - Genetics, Physiology, Agronomy and Nitrogen

A screening for genes involved in root nodule senescence has resulted in the isolation of the senescence-associated nodulin 1 (SAN1) multigene family from soybean. The SAN1-encod‐ ed proteins display sequence resemblance and highly conserved motifs with plant 2-oxoglu‐ tarate-dependent dioxygenases (2-ODDs). SAN1A is downregulated whereas SAN1B is upregulated during senescence induced by treatment with fixed nitrogen or darkness. The expression of the SAN1genes is not found only in nodules, signifying a more general role in

Soybean seeds contain only low levels of sulfur-containing amino acids. Although expressed in various tissues throughout the plant, there is an abundant expression of the APS reduc‐ tase gene and activity of the encoded protein in the early developmental stages of soybean seed, which decreases as the seed matures. Sulfur and phosphorus deprivation and coldtreatment elevate the expression level, while nitrogen starvation reduces APS reductase mRNA transcript and protein levels. This study allows an insight into the sulfur assimila‐

Analysis of the ATP sulfurylase ATPS clone isolated from a soybean seedling cDNA library revealed an open-reading frame, encoding a 52-kDa polypeptide with an Nterminal chloroplast/plastid transit peptide. ATP sulfurylase mRNA was present with the highest abundance in root tissue. mRNA accumulated and the specific activity of ATP sulfurylase in root tissue was enhanced by cold treatment. The transcript levels and specific activity of the enzyme dropped during the later stages of seed develop‐ ment. Augmenting the expression levels of this key enzyme during soybean seed de‐

**48. Genes related to 2-oxoglutarate-dependentdioxygenases**

Soluble soybean polysaccharide (SSPS) was fractionated into two sub-fractions, a highmolecular-weight fraction (HMF) and a low-molecular-weight fraction (LMF) by the ethanol-extraction method. The major constituent of HMF was a large polysaccharide with covalently-attached peptides, probably corresponding to the intact SSPS mole‐ cule. LMF was composed of free peptides and saccharides of small size, which might have occurred as by-products during the process of SSPS production. HMF exhibited high ability to emulsify oil droplets and stabilize alpha-casein dispersions in an acid‐ ic pH region. LMF showed lower activity in this regard although but it had higher potency in preventing the oxidation of emulsified lipids. The data indicate that HMF and LMF possess dissimilar structural and functional characteristics, and that the combination of the two sub-fractions displays the multiple functions of commercial SSPS [55].
