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QTL mapping for glycinin and #-conglycinin contents in soybean (Glycine max L. Merr.) Yujie Ma, Guizhen Kan, Xinnan Zhang, Yongli Wang, Wei Zhang, Hongyang Du, and Deyue Yu J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.6b00167 • Publication Date (Web): 12 Apr 2016 Downloaded from http://pubs.acs.org on April 14, 2016
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Journal of Agricultural and Food Chemistry
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QTL mapping for glycinin and β-conglycinin contents in soybean (Glycine max L.
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Merr.)
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Yujie Ma,1 Guizhen Kan,1 Xinnan Zhang,1 Yongli Wang,2 Wei Zhang,1 Hongyang
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Du,1 and Deyue Yu1,*
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1
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Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing
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210095, China
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2
9
China
National Center for Soybean Improvement, National Key Laboratory of Crop
Biofuels Institute, School of the Environment, Jiangsu University, Zhenjiang 212013,
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* To whom correspondence should be addressed. E-mail:
[email protected];
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Telephone Number: +86-25-84396410; Fax: +86-25-84396410
12 13
E-mail addresses of co-authors:
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Yujie Ma:
[email protected] 15
Guizhen Kan:
[email protected] 16
Xinnan Zhang:
[email protected] 17
Yongli Wang:
[email protected] 18
Wei Zhang:
[email protected] 19
Hongyang Du:
[email protected] ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
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Abstract: Compared to β-conglycinin, glycinin contains three to four times the
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methionine
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approximately 40% and 30%, respectively, of the total storage protein in soybean.
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Increasing the soybean storage protein content while improving the ratio of glycinin
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to β-conglycinin is of great significance for soybean breeding and soy food products.
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The objective of this study is to analyze the genetic mechanism regulating the
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glycinin and β-conglycinin contents of soybean by using a recombinant inbred line
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(RIL) population derived from a cross between Kefeng No.1 and Nannong 1138-2.
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221 markers were used to map quantitative trait loci (QTLs) for glycinin (11S) and
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β-conglycinin (7S) contents, the ratio of glycinin to β-conglycinin (RGC) and the sum
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of glycinin and β-conglycinin (SGC). A total of 35 QTLs, 3 pairs of epistatic QTLs
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and 5 major regions encompassing multiple QTLs were detected. Genes encoding the
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subunits of β-conglycinin were localized to marker intervals sat_418-satt650 and
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sat_196-sat_303, which are linked to RGC and SGC; marker sat_318, associated with
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11S, 7S and SGC, was located near Glyma10g04280 (Gy4), which encodes a subunit
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of glycinin. These results, which take epistatic interactions into account, will improve
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our understanding of the genetic basis of 11S and 7S contents and will lay a
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foundation for marker-assisted selection (MAS) breeding of soybean and improving
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the quality of soybean products.
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Keywords: soybean; glycinin; β-conglycinin; QTL; epistatic QTL
and
cysteine
(sulfur-containing
amino
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acids),
accounting
for
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Journal of Agricultural and Food Chemistry
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Introduction
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One-third of the global population suffers from malnutrition and disease due to
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deficiencies in protein, vitamins and certain micronutrients,1 and enhancing the
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nutritional quality of food is a major approach to resolving this issue. The protein
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content is the key factor influencing the nutritional quality of grain crops, and
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researchers have successfully increased the content of some essential amino acids in
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crop plants using genetic engineering.2 Nonetheless, crops such as maize, rice, wheat
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and soybean differ in protein contents, which is a complex quantitatively inherited
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trait that is controlled by the environment, genotype, and interaction between the
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environment and genotype.3
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Soybean [Glycine max (L.) Merr.], one of the most important crops worldwide,
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provides essential proteins and amino acids for humans and animals. Foods made
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from soy, mainly soymilk and tofu, have health benefits for humans, and consumption
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of these foods is increasing. The proportion of protein in soybean is approximately
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35-42%,4 and based on their sedimentation coefficient at 0.5 M ionic strength,
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soybean storage protein can be divided into 2S, 7S, 11S and 15S fractions.5 The main
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storage proteins are 11S and 7S globulins, which account for approximately 40% and
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30%, respectively, of the total seed storage protein. The former is glycinin, whereas
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β-conglycinin comprises the majority of the 7S fraction.6
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Glycinin (11S) usually exits in the form of a hexamer of 360 kDa that consists of
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acidic and basic subunits. In contrast, β-conglycinin (7S) usually exists as a trimer of
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α, α’ and β subunits that is approximately 180 kDa.7 Due to a lack of sulfur-containing
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amino acids, the β subunit is very poor in nutritional quality; in addition, 11S contains
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three to four times more methionine and cysteine than 7S. Thus, simultaneously
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promoting the accumulation of 11S globulin and inhibiting the accumulation of 7S
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Journal of Agricultural and Food Chemistry
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globulin in soybean seed represents a way to increase the content of sulfur-containing
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amino acids and to improve the nutritional quality of soybean. The different storage
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proteins have different characteristics, including heating stability and gel strength in
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soy food because of differences in their molecular structures, isoelectric points and
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amino acid compositions.8 Indeed, the quality of tofu and soymilk is affected by
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different levels of 11S and 7S globulins, and many studies about the relationship
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between storage proteins and soy foods have been reported. Yang and James9 showed
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that the absence of a particular 11S globulin polypeptide and the subsequent protein
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subunit composition affected the texture and water-holding characteristics of tofu. Ma
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et al.10 demonstrated that the ratio of glycinin to β-conglycinin is significantly
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positively correlated with soymilk sensory attributes. Furthermore, Osman et al.11
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studied the preservative action of 11S and 7S globulins on raw bovine milk and
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deduced that 11S could be utilized as a natural preservative in raw milk if permitted.
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Therefore, 11S and 7S determine soybean nutritional quality and functional
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characteristics.
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The traditional method for measuring 7S and 11S involves liquid chromatography,12
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which has the disadvantage of being time consuming and expensive. In contrast, the
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enzyme-linked immunosorbent assay (ELISA) used in the present study is time saving
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and exhibits a high sensitivity for detecting 11S and 7S.13 In addition, traditional
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breeding methods based on phenotypic selection are easily affected by environmental
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factors, gene interactions and interactions between the genotype and environment.
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Therefore, breeders are paying more attention to MAS, which is more rapid and
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accurate than traditional methods, and the application of molecular markers has
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enabled the exploration of quantitative trait loci (QTLs) for traits of yield,14
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quality15-17 and resistance to stress.18 In general, an individual QTL can be described
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Journal of Agricultural and Food Chemistry
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as ‘major’ or ‘minor’ according to the proportion of the phenotypic variation that it
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explains (based on the r2 value). A major QTL has a relatively large r2 value, such
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as >10%, whereas a minor QTL has a small value, r2