Cloning And Functional Analysis Of Emp11 And ZmSmk3 Controlling Kernel Development In Maize

The correlative characters of maize kernels are complex quantitative traits and the kernel size and plumpness are regulated by the development of kernel,which are affecting maize yield.So far,many genes related to kernel development are cloned in maize,but the regulatory mechanism of seed development is still unclear.The discovery of these genes will contribute to deciphering the molecular mechanism of seed development in maize.Our study cloned two new genes Emp11 and Zm Smk3,belonging to PPR and m TERF family,respectively.Both of the two genes influence the development of kernels.We analyzed their function by molecular experiments.The main results were as follows:1.Cloning and functional analysis of Emp11 for kernel development in maize.The development of homozygous emp11-1 kernels was arrested early,the basal endosperm transfer layer was abnormal and the starch accumulation was delaying,which resulting in shrunken and empty pericarp phenotype.The mutant phenotype was controlled by a single recessive nuclear gene and the allelism test and RNAi transformation further demonstrated the mutation of Emp11 can lead to defective seeds.Emp11 was expressed constitutively,with higher levels in the ear,ovary,embryo(especially in SAM),aleurone and BETL in the endosperm.Emp11 encode a P-type PPR protein located in mitochondria.The loss of Emp11 showed a failure in intron splicing of nad1 four introns and a severe reduction in complex I assembly and activity,resulting in abnormal structure and disturbed function of mitochondria,alternate oxidase pathway was activated as compensation mechanism of energy supply,which seriously impaired kernel development,and showed empty pericarp seeds in maize.2.Cloning and functional analysis of Zm Smk3 for kernel development in maize.Zmsmk3 behaved as a monogenic recessive trait and the Mu transposon in the promoter of Zm Smk3 resulted in small kernels.The Zm Smk3 expressed in all tissues tested,with higher levels in the stem,ear,ovary,embryo and BETL in the endosperm.Zm Smk3 encoded an m TERF protein with two m TERF motifs and the protein located in mitochondria.The loss of Zm Smk3 showed a failure in intron splicing of nad4 intron1 and nad1 intron4,exhibited a reduction in complex I assembly and activity and impaired mitochondria structure,which resulted in oxidative phosphorylation disturbance.Under this low energy condition,the alternative respiratory pathway is activated.The DEGs related to starch biosynthetic pathway and zein gene family were down-regulated in the mutant.Interestingly,Zm Smk3 may also participate in responses to abiotic stress.