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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 is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

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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

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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

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E-mail addresses of co-authors:

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Yujie Ma: [email protected]

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Guizhen Kan: [email protected]

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Xinnan Zhang: [email protected]

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Yongli Wang: [email protected]

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Wei Zhang: [email protected]

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Hongyang Du: [email protected]

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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