Genetic interactions regulating seed phytate and oligosaccharides in soybean (Glycine max L.)

Abstract

Two low-phytate soybean (Glycine max (L.) Merr.) mutant lines-V99-5089 (mips mutation on chromosome 11) and CX-1834 (mrp-l and mrp-n mutations on chromosomes 19 and 3, respectively) have proven to be valuable resources for breeding of low-phytate, highsucrose, and low-raffinosaccharide soybeans, traits that are highly desirable from a nutritional and environmental standpoint. A recombinant inbred population derived from the cross CX1834 x V99-5089 provides an opportunity to study the effect of different combinations of these three mutations on soybean phytate and oligosaccharides levels. Of the 173 recombinant inbred lines tested, 163 lines were homozygous for various combinations of MIPS and two MRP loci alleles. These individuals were grouped into eight genotypic classes based on the combination of SNP alleles at the three mutant loci. The two genotypic classes that were homozygous mrp-l/mrp-n and either homozygous wild-type or mutant at the mips locus (MIPS/mrp-l/mrp-n or mips/mrp-l/mrp-n) displayed relatively similar~55% reductions in seed phytate, 6.94 mg g-1 and 6.70 mg g-1 respectively, as compared with 15.2 mg g-1 in the wild-type MIPS/MRP-L/MRP-N seed. Therefore, in the presence of the double mutant mrp-l/mrp-n, the mips mutation did not cause a substantially greater decrease in seed phytate level. However, the nutritionally-desirable high-sucrose/low-stachyose/low-raffinose seed phenotype originally observed in soybeans homozygous for the mips allele was reversed in the presence of mrp-l/mrp-n mutations: homozygous mips/mrp-l/mrp-n seed displayed low-sucrose (7.70%), high-stachyose (4.18%), and the highest observed raffinose (0.94%) contents per gram of dry seed. Perhaps the block in phytic acid transport from its cytoplasmic synthesis site to its storage site, conditioned by mrp-l/mrp-n, alters myo-inositol flux in mips seeds in a way that restores to wild-type levels the mips conditioned reductions

Raffinose Family Oligosaccharides: Friend or Foe for Human and Plant Health?

“…However, these food processing methods are time-consuming and lead to loss of nutrients and sometimes have consumer acceptability issues. Therefore, alternative approaches from a breeding perspective have been used to select cultivars with a low level of raffinose and stachyose ( Obendorf and Górecki, 2012 ; Redekar et al, 2020 ) or inhibiting galactinol synthase activity ( Bock et al, 2009 ) and over-expression of α -galactosidase in seeds by genetic manipulation ( Polowick et al, 2009 ). Screening legumes for low RFOs contents has been carried out in many species such as chickpea ( Raja et al, 2015 ; Gangola et al, 2016 ), lentil ( Tahir et al, 2011 , 2012 ), pea ( Peterbauer et al, 2003 ), and soybean ( Blackman et al, 1992 ; Dierking and Bilyeu, 2008 ; Obendorf and Górecki, 2012 ).…”

Network Inference of Transcriptional Regulation in Germinating Low Phytic Acid Soybean Seeds

“…In contrast to the mrp mutations, mips mutations, in addition to reducing seed phytic acid also result in reduced raffinosaccharides and increased sucrose, a unique and highly desirable soybean seed phenotype ( Saghai Maroof and Buss, 2011 ; Redekar et al, 2020 ). Therefore, there is added value in developing soybean mips lines with good field performance and yield.…”

Optimizing raffinose family oligosaccharides content in plants: A tightrope walk

“…The RFOs and phytic acid biosynthetic pathways share a common intermediate (myoinositol). Low phytic acid mutants have increased myoinositol levels, possibly contributing to RFOs accumulation ( Zhawar et al., 2011 ; Redekar et al., 2020 ). Higher sucrose concentrations also increase the accumulation of raffinose ( Borisjuk et al., 2002 ).…”

“…The content and composition of RFOs vary across the genotypes and environmental conditions ( Table 1 ) ( Kumar et al., 2010 ; Redekar et al., 2020 ). Seeds are the primary storage site for RFOs.…”