Characterization and map-based cloning of miniature2-m1, a gene controlling kernel size in maize

摘要

Kernel development plays an important role in determining kernel size in maize.Here we present the cloning and characterization of a maize gene,nitrate transporter1.5(NRT1.5),which controls small kernel phenotype by playing an important role in kernel development.A novel recessive small kernel mutant miniature2-m1(mn2-m1)was isolated from self-pollinated progenies of breeding materials.The mutant spontaneously showed small kernel character arresting both embryo and endosperm development at an early stage after pollination.Utilizing 21 polymorphic SSR markers,the mn2-m1 locus was limited to a 209.9-kb interval using 9176 recessive individuals of a BC1 segregating population from mn2-m1/B73.Only one annotated gene was located in this 209.9 kb region,Zm00001 d019294,which was predicted to encode nitrate transporter1.5(NRT1.5).Allelism tests confirmed that mn2-m1 was allelic to miniature2-m2(mn2-m2)and miniature2-710 B(mn2-710 B).The mn2-m1 and mn2-m2 alleles both had nucleotide deletions in the coding region resulting in premature termination,and the mn2-710 B allele had some missence mutations.Subcellular localization showed that Miniature 2(MN2)is localized in the plasma membrane.Quantitative real-time PCR(qRT-PCR)analysis revealed that the expression of MN2 and some genes involved in the basal endosperm transfer layer(BETL)and embryo surrounding region(ESR)development were affected in mn2-m1 seeds.These results suggested that MN2 plays an important role in maize seed development.