The present invention relates to isolated nucleic acid molecules and their corresponding encoded polypeptides able confer the trait of modulated plant size, vegetative growth, organ number, plant architecture, sterility or seedling lethality in plants. The present invention further relates to the use of these nucleic acid molecules and polypeptides in making transgenic plants, plant cells, plant materials or seeds of a plant having such modulated growth or phenotype characteristics that are altered with respect to wild type plants grown under similar conditions.