The effects of the deficiency of the allergenicα-subunit on soybean amino acid(AA)composition were studied using the cultivar Dongnong 47(DN47)as a genetic background.The near-isogenic line(NIL)NIL-DN47-Δα of DN47,with an introgression of theα-null trait allele from the high protein donor parent RiB,was created by marker assisted background selection and used to investigate the AA content and nutritional quality.The contents of crude protein,the total AAs,the total essential amino acids(EAAs)and sulfur-containing(Met and Cys)AAs increased by 4.11%,4.16%,5.20% and 11.96%,respectively in NIL-DN47-Δα compared with DN47.Analyses of the total EAAs(TEAAs)and the EAA index(EAAI)revealed that both parameters in NIL-DN47-Δα were higher than those in DN47.The null-allele of theα-subunit positively affected the AA scores.The quantitative changes in free AAs(FAAs)in the developing seeds of NIL-DN47-Δα and DN47 were compared as of 15 days after flowering(DAF)until maturity.The results showed that the total FAA content in NIL-DN47-Δα was significantly higher than that in the DN47 throughout the late maturation stage(40-60 DAF)of seeds.The high concentration of the FAAs in cgy-2 mutant seeds was a consequence of the high rates of synthesis and/or accumulation of individual FAAs during seed maturation where 25 DAF was an important turning point in the accumulation of the FAAs.The FAA contents of single soybeanα-null,double(α+α′)and triple(α+α′+group I)-null mutant combination lines were investigated.In all of these combinations,introduction of the cgy-2 gene invariably raised the FAA content of mature seeds above that of the DN47.In summary,the enhanced protein quality in cgy-2 mutants resulted from several factors.(1)There was a general increase in the contents of most AAs and FAAs in NIL-DN47-Δα.(2)The induced synthesis of free Arg contributed effectively to the high FAAs of various storage-protein-deficiency mutants.For example,in the S2(null α,group I),the free Arg content was seven times as much as
Studies have shown that the three subunits of β-conglycinin are the main potential allergens of soybean sensitive patients.And β-conglycinin has adverse effects on nutrition and food processing.So solation and production of lines with lowerβ-conglycinin content has been the focus of recent soybean breeding projects.Soybean lines with deficiency in one or all subunits of β-congIycinin have been obtained.An effective and rapid system to identify such mutations will facilitate genetic manipulation of the β-conglycinin subunit composition.Here,two segregating F2 populations were developed from crosses between Cgy-1/cgy-1(CC),anα'-lacking line(△α'),and DongNong 47(DN47),a wild-type(Wt)Chinese soybean cultivar with normal globulin components,and Cgy-2/cgy-2(CB),an a-lacking line(△α),and DN47.These populations were used to estimate linkage among the egy-1(conferring α'-null)and cgy-2(α-null)loci and simple sequence repeat(SSR)markers.Seven SSR markers(Sat_038,Satt243,Sat_307,Sat_109,Sat_231,Sat_108 and Sat_190)were determined to co-scgregate with cgy-1,and six SSR markers(Satt650,Satt671,Sat_418,Sat_170,Satt292 and Sat_324)co-segregated with cgy-2.Linkage maps being composed of seven SSR markers and egy-1 locus,and six SSR markers and the cgy-2 locus were then constructed.It assigned that the egy-1 gene to chromosome 10 at a position between Sat_307 and Sat_231,and the cgy-2 gene to chromosome 20 at a position between Satt650 and Satt671.These markers should enable map-based cloning of the egy-1 and cgy-2 genes.For different subunit-deficiency types[α'-null,α-null and(α'+α)-null types],the two sets of SSR markers could also detect of polymorphism between three normal cultivars and seven related mutant lines.The identification of these markers is great significance to the molecular marker-assisted breeding of soybean/9-conglycinin subunits.
Pang ZeLi Ming-xueZhou Jin-taoQiu Zhen-dongSong Ying-jiSong Yan-ruWaqar AhmedSong BoLiu Shan-shan
