Obtainment Of Kernel Mutants Based On MNU Mutagenesis Of Pollen Germ Cells Of Maize And Their Characterization

Maize(Zea mays L.),one of the major food crops,is the important resource widely used in agriculture,food,feed,energy and many other fields.With the shift of life sciences to the era of post-genomic researches,maize science has begun to enter the functional-genomic researches for revealing expression of functional genes and their genetic mechanisms regulating characters,the cultivation of maize cultivars is also tending to achieve diversified breeding objectives.Maize genome contain about 32,000 genes(http://www.maizegdb.org),most of them are functional genes concerning the character expression in maize.Development and utilization of maize mutants have promoted the identification and functional analysis of some genes,but biological functions of most maize genes are still unknown.One of main reasons causing this situation is insufficiency of mutant materials due to lower efficiency of maize mutagenesis.Recently,the technology for N-methyl-N-nitrosourea(MNU)mutagenesis on pollen germ cells of maize has been established in our laboratory.This technology has the significantly improved efficiency of broad-spectrum induction of genic mutations,compared with the reported EMS mutagenesis of maize.Its application can provide the efficient technical-support for large-scale development of various mutant materials for the functional-genomic researches and breeding of maize.Characters in maize seed,as the basic factors determining the yield and quality of maize kernel and the value of maize-derived products,have attracted long-term attention in maize genetic and breeding researches.About400 genes concerning the expressions of kernel characters in maize have been registered in the Maize Genetics and Genomics Database.In order to provide the various genic-mutant materials for identifying the unknown genes regulating the kernel characters expressions,in this study,41 homozygous kernel mutants of maize were obtained,characterized and named as ZMKM series,after screening the 346 M2 kernel populations and their progeniesderived by the MNU treatment of pollen germ cells of the wild type maize inbred line,A378.Compared with A378,the ZMKM series mutants showed the various alterations of kernel characters and endosperm starch properties,and also had the changes in culm,leaf or panicle types of characters.The ZMKM1 and ZMKM2 were the shrunken-kernel mutants,which showed the depression,opacity and reluster characters in kernels.The ZMKM3-ZMKM5 were the waxy-endosperm mutants with the cream-like white endosperms and depressed embryos.The ZMKM6-ZMKM9 were the white-endosperm mutants,showing the characters white endosperms and floury bottom.The ZMKM10-ZMKM18 showed the characters of abnormal yellows such as golden,orange or deep yellows in endosperms;among them,the ZMKM10 and ZMKM11 also had the concave characteristics at the base of endosperms,the ZMKM12 also had the characteristics of square kernels,the ZMKM15 and ZMKM16 also had the characteristics of round kernels.The ZMKM19-ZMKM24 were embryonic form mutants;among them,the ZMKM19-ZMKM21 and ZMKM22-ZMKM24 showed the wrinkle and depressions in embryos respectively.The ZMKM25-ZMKM37 were the mutants for seed-coats colors;among them,the ZMKM25-ZMKM33 and the ZMKM34-ZMKM37 showed the stripe and the uniform color change in seed coats.The ZMKM38-ZMKM41 were the small-kernel mutants which also had the characteristics of depression and abnormal yellow deposition in bottoms,three of them also had the round kernel characteristic.In order to explore the qualitative characters of endosperm components in kernel mutants,we further analyzed the properties of endosperm starch in the six representative mutants,ZMKM1,ZMKM5,ZMKM34,ZMKM8,ZMKM17 and ZMKM32.Compared with A378,the ZMKM1,significantly reduced the contents of amylose,amylopectin and total starch,showing the characteristics of globular and density-increased starch granules.The ZMKM5 and ZMKM34,that decreased the amylose and increased the amylopectin and total starch showed the depression increase and flocculent attachment on starch granule surface.The ZMKM8,ZMKM17 and ZMKM32,that all significantly increased the amylose content,showed the characteristics of the pointedness weakening on starch granules surface.The mutants obtained in this study can be used in the genetic and breeding researches of maize,including the genetic analysis,proteomic characterization,transcriptome and c DNA identification,gene cloning and coding protein analysis,and new cultivar cultivation.Their application is expected to promote the identification of unknown functional-genes,the understanding of genetic mechanism kernel-character expressions in kernel and the realization of breeding goal for diversification of kernel quality of corn.