Provided are method of increasing oil content, growth rate, biomass, yield and/or vigor of a plant. The methods are effected by upregulating in the plant an expression level of a polypeptide comprising an amino acid sequence at least 90% homologous to the amino acid sequence selected from the group consisting of SEQ ID NOs: 199, 166-198, 200-221, 229-307, 311-330, 351-353, 355-361, 363-364, 366-368, 218, 222-228, 308-310, 350, 354, 362, 365, 523-649, 786-920, 1047 and 1048. Also provided are polynucleotides, nucleic acid constructs, polypeptides and transgenic plants expressing same which can be used to increase oil content, growth rate, biomass, yield and/or vigor of a plant and produce oil.