The Roles of the NANA and LEPIDA Genes in Regulating the Stem Growth in Arabidopsis thaliana

Genetic, physiological, and morphological studies of dwarf mutants of Arabidopsis thaliana (L.) Heynh. from the collection of the Department of Genetics and Breeding, Moscow State University, showed that the NA and LE genes are involved in regulating elongation of internode cells and sensitivity to various hormones. The na mutation suppressed stem growth only in the presence of the active LE gene. The absence of the LE activity (in the lele homozygote) restored stem growth of the na mutant to the level characteristic of thele-2 mutant, and a decrease inLE activity (in LE/le heterozygote) almost completely suppressed the na phenotype. Phenotypic analysis of homozygous double mutants and heterozygotes obtained by crossing the na and le-2 mutants showed that the recessive le-2 allele has an epistatic effect on the semidominant na allele and that the genes possibly control consecutive steps of one biochemical pathway or one morphogenetic process. A hypothetical scheme was proposed for the interaction of the NA and LE gene products.