Comparative Proteomic Analysis Of Seed Salt-soluble Proteins Accumulation Between Maize Hybrids And Their Parental Inbred Lines

Cereal crops contain large amounts of storage proteins,which have important impacts on their nutritional quality for humans and livestock.Maize is one of the most important cultivated cereals in China.In agricultural production,the maize hybrids are always cultivated mainly due to superior performance of the hybrids.Although many studies have focused on researching the heterosis of maize,the genetic mechanism of heterosis is still not very clear.Besides,these studies mainly focus on the agronomic traits such as crop yield,but little on physiological and biochemical research of heterosis.Maize seeds contain about 10% of the protein,of which 60-80% is storage proteins,and mainly exist in the embryos.However,the protein accumulation patterns specific to salt-soluble proteins(SSPs)in maize embryo between hybrids and their parental inbred lines have not yet been reported.In the present study,two elite inbred lines in China Zheng 58 and Chang 7-2,and their reciprocal hybrids Zheng 58 × Chang 7-2 and Chang 7-2 × Zheng 58 were used as materials,and a proteomic approach was used to identify differentially accumulated SSPs in maize embryo between the hybrids and their parental inbred lines.Besides,the expression patterns of nonadditive accumulated salt-soluble proteins in the hybrids were analyzed.The main results are as follows:(1)From the protein profiles of 2-DE,we found the accumulation patterns of salt-soluble proteins in the hybrids were more similar to their corresponding female parents compared to the male parents.A total of 12 protein spots with at least two-fold abundance change between the reciprocal hybrids and their parental inbred lines were analyzed by using PDQuest 8.0 software.After MS/MS identification,we found most of these differentially accumulated proteins were storage proteins,including some globulin and globulin precursors,and a chaperone protein—small heat shock protein was also identified.These proteins were mainly involved in biological processes such as tissue development,energy metabolism and stress response.(2)Among the 12 differentially accumulated protein spots,nine spots displayed nonadditive accumulation in at least one hybrid.The results of statistical analysis showed that the dominance and partial dominance were the major patterns for the nonadditively accumulated SSPs in both of the hybrids.However,the accumulation pattern for the same protein in the different hybrid combinations was different.(3)The subunits composition of vicilins in the hybrids and their parental inbred lines were analyzed,the results showed that the accumulation patterns of vicilins in the hybrids were more similar to the female parents compared to the other parents.Five polypeptides with molecular weights of about 71,63,50,43 and 29 k Da were isolated from the nature form of vicilins,and no disulfide bond was found in them.In conclusion,in this study,the salt-soluble proteins were extracted and purified from the embryos of the reciprocal hybrids and their parental inbred lines.After both the qualitative and quantitative analysis,we found that the accumulation patterns of the salt-soluble proteins in the reciprocal hybrids revealed matroclinous inheritance.This phenomenon was also verified after a further analysis to the vicilins.The study will provide new information and new ideas for analyzing the mechanism of maize heterosis.