Effect of herbicidal application of 2,4-dichlorophenoxyacetic acid in Arabidopsis

The whole genome expression pattern of Arabidopsis in response to the auxinic herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was evaluated using the Affymetrix ATH1-121501 array. Arabidopsis plants were grown in vitro and were exposed to 1 mM 2,4-D for 1 h, after which time gene transcription levels were measured. In response to the treatment 148 genes showed increased levels of transcription and concurrently 85 genes showed decreased levels of transcript. Genes which showed significant change in transcription levels belonged to the following functional categories: transcription, metabolism, cellular communication and signal transduction, subcellular localisation, transport facilitation, protein fate, protein with binding function or cofactor requirement and regulation of/interaction with cellular environment. Interestingly 25.3% of the genes regulated by the treatment could not be classified into a known functional category. The data obtained from these experiments were used to assess the current model of auxinic herbicide action and indicated that 2,4-D not only modulates the expression of auxin, ethylene and abscisic acid (ABA) pathways but also regulates a wide variety of other cellular functions.