Abstract: The present invention relates to polynucleotides and their use in methods of increasing the carotenoid content of seeds. In particular the invention provides a polynucleotide comprising: (a) a region which comprises as operably linked components (i) a promoter which provides for seed preferred expression; and (ii) a nucleotide sequence derived from a bacterium which sequence encodes a carotene desaturase; and (iii) a transcription termination region; and (b) a further region which comprises as operably linked components (i) a promoter which provides for seed preferred expression; and (ii) a nucleotide sequence encoding a phytoene synthase which sequence is derived from a plant selected from the group consisting of: tomato (Lycopersicon sp.); pepper (Capsicum sp.); maize (Zea sp.) and rice (Orzya sp.) or a bacterium; and (iii) a transcription termination region. The disclosed polynucleotides are particularly suitable for use in production of rice seed which comprise high amounts of coloured carotenoids.

Abstract: A recombinant plant genome contains a gene cascade such that it is incapable of producing a mature plant but requires the presence of a chemical inducer. The gene cascade includes a gene switch which is inducible by external application of a chemical inducer and which controls expression of a gene product which affects expression of a second gene in the genome. Survival or development of the plant is dependant upon either expression or non-expression of the second gene and application of the inducer, therefore, selects whether or not the plant develops. In one example the second gene encodes a cytotoxic molecule and expression of that gene is fatal to the plant. In another example the second gene encodes a desirable characteristic which may be excised selectively by applying or withholding chemical application. The second gene may be placed under control of a development regulated promoter.