Arsenic toxicity is well known in plants; however, little is known about the mechanisms of the toxicity or the genetic functions that confer that toxicity. In this study, using a combination of forward and reverse genetics, I isolated three Arabidopsis (Arabidopsis thaliana) mutants that were hypersensitive to arsenate, arsenate overly-sensitive 1 (aos1), plastid lipoamide dehydrogenase 2 (ptlpd2) and mitochondrial lipoamide dehydrogenase 2 (mtlpd2). Each mutant displayed decreased root and shoot growth, as well as enhanced accumulation of anthocyanins during arsenate exposure, compared with wild-type (WT) plants. The aos1 mutant was found to arise from a 107 kb DNA rearrangement that disrupted the plastid lipoamide dehydrogenase 1 (ptLPD1) gene, which encodes the E3 subunit of the plastid pyruvate dehydrogenase complex (ptPDC). The T-DNA insertion in aos1-1 co-segregated with the enhanced arsenate sensitivity and three independent transgenic lines carrying T-DNA insertions in ptLPD1 were more sensitive to arsenate than WT plants, establishing that mutation of ptLPD1 is responsible for arsenate sensitivity in aos1. Also, the function of ptLPD2 in respect to arsenate sensitivity was demonstrated by the enhanced arsenate sensitivity of two independent ptlpd2 loss-of-function mutants plants. Similarly, two independent mtlpd2 T-DNA insertional mutants displayed arsenic hypersensitivity, with the T-DNA insertion in mtlpd2-2 co-segregating with the enhanced arsenate sensitivity phenotype, indicating that mutation of mtLPD2 was responsible for the increased arsenate sensitivity. The mtlpd2 mutant also exhibited decreased amounts of mtLPD and total mtLPD activity. aos1, mtlpd2 and ptlpd2 mutant plants were also found to be more sensitive to arsenite than WT plants, but were same as wild-type plants in sensitivity to zinc, copper, nickel and cadmium.
|Qualification||Doctor of Philosophy|
|Publication status||Unpublished - 2009|