Expression Of Mitochondrial Genes In Nucleus In Arabidopsis Thaliana And Functional Analysis Of Maize Gene ZmSpx1

Mitochondria are important organelles in eukaryotic cell,and are considered the powerhouses of the cell that provide the energy necessary for cell activities.According to the endosymbiont hypothesis,mitochondria were once free-living oxygen-using prokaryotes,and during the evolution,most mitochondrial genes have been transferred to the nucleus.The mitochondria now only retain a small portion of their ancestral genome,and the expression of mitochondrial genes always needs post-transcriptional processing by nucleus-encoded factors.In plant,the processing of mitochondrial genes are necessary for the function of mitochondria,and dysfunction of processing often leads to severe consequences for plant development and fertility.To explore the function of the transfer of mitochondrial genes and investigate the coordination between plant development and mitochondria,we generated transgenic plants of eight mitochondrial genes using Arabidopsis thaliana,all the eight genes were edited and spliced,and to target mitochondria we used the first 29 amino acids of yeast(Saccharomyces cerevisiae)cytochrome c oxidase IV(Sccox4)as the signal peptide.Analysis of the relative mRNA transcript abundance of the genes Atnad4 and Atnad7 in transgenic plants revealed that,although the genes in nucleus were expressed stably,the expression level was not higher than wild-type plants,except the Atnad7 transgenic line 26.Our data also showed that there were no significant differences in the development between transgenic plants and wild-type plants.In addition,we explored the function of maize gene ZmSpxl,which encodes a SPX protein.Protein ZmSPX1 was obtained by screening the cDNA library of maize ear with yeast two-hybrid for the interacting protein of DELLA protein d8.DELLA proteins act as plant growth repressors in GA signaling pathway.In maize,both GA-deficient mutants and GA insensitive mutant D8 carry the bisexual flowers in ear,which indicates ZmSPXl may play an important role in the sex determination of flowers in ear.We obtained mutant Zmspxl from the UniformMu population,and our results showed the flowers in ear of Zmspxl are normal.Zmspxl has two alternative splicing forms,one is normally spliced,the other lack the 5' 80 nucleotides of the third exon.The abnormal splicing form encodes a mutant protein with the structure of SPX domain was changed and the interaction with DELLA protein d8 was lost.