Dissertation Research: Chloroplast Genome Evolution in a Non-photosynthetic Plant

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The genus Conopholis belongs to a family of parasitic plants, the Orobanchaceae. The plants are obligate parasites on other plants, from which they derive all of their nutrients and water. Possibly as a direct result of this parasitism these plants have lost the ability to photosynthesize and lack the characteristic green color conferred by the presence of chlorophyll. The plastids (the organelle which in green plants houses the photosynthetic metabolism and has its own circular genome containing about 120 genes, including some of those involved in photosynthesis) of Conopholis contain a genome only a third the size of that in green plants and have lost several important photosynthesis genes. This has occurred through the accumulation of several large deletions of DNA. The large amount of variation in the plastid genome detectable between different populations of Conopholis indicate that it is continuing to evolve at an accelerated rate. DNA sequencing methods will be used to investigate how these deletions have occurred and what has happened to plastid genes which have not been deleted. Those that remain intact will be investigated for non-photosynthetic functions. The evolution of the non-functional photosynthesis genes remaining in the plastid genome will be compared with their counterparts in the nuclear genome in order to find out if they have had different fates as a result of different molecular processes occurring in these two genomes.