Complex haploinsufficient interaction between APC11 and CYCLIN A1;2/TARDY ASYNCHRONOUS MEIOSIS in embryo development and seed germination in Arabidopsis

Abstract

Background:Complex haploinsufficiency is characterized by individuals with two heterozygous loci producing a phenotype that is not seen in either of the corresponding single-locus heterozygous individuals. The mutants of the anaphase-promoting complex/cyclosome (APC/C) subunit geneAPC11and the mitotic cyclin geneCYCLIN A1;2/TARDY ASYNCHRONOUS MEIOSIS(TAM) inArabidopsis thalianaare embryo-lethal and defective in meiosis, respectively, but their heterozygous single mutants do not exhibit defective embryo development and seed germination.Methods:Crosses between two heterozygousapc11mutant alleles and two homozygoustammutant alleles, and between two heterozygousapc11mutant alleles and aTAM:TAM-GFPline were conducted. Phenotypes of the F1seeds were analyzed by light microscopy.Results:We found that F1embryos from the crosses between heterozygousapc11-1(APC11/apc11-1) and homozygoustam-2(tam-2/tam-2) or betweenAPC11/apc11-2andtam-2/tam-2were morphologically normal but all the seeds failed to germinate. F1embryos from the crosses betweenAPC11/apc11-2andtam-1/tam-1(weaker allele thantam-2) produced morphologically normal seeds that germinated to form mature plants. However, F1embryos from the crosses betweenAPC11/apc11-1andtam-1/tam-1were abnormal and the seeds failed to germinate. Moreover, F1embryos from the crosses betweenAPC11/apc11-1and aTAM:TAM-GFPline were arrested at early developmental stages while F1embryos from the crosses betweenAPC11/apc11-2and theTAM:TAM-GFPline appeared fully developed but the seeds failed to germinate.Conclusions:Our observations indicate that theapc11andtammutants have an allele-dependent complex haploinsufficient relationship in embryo development and seed germination.