Ethylene is a plant hormone that regulates multiple processes, including plant growth and pathogen defense. Dong et al. studied the response of Arabidopsis to exposure to harpin, a protein produced by certain plant pathogenic bacteria that causes pleiotropic responses. In Arabidopsis, harpin causes root elongation, increases in plant size and mass, and resistance to aphid infestation. Using reverse transcription polymerase chain reaction (RT-PCR), the authors demonstrated that many of the genes induced by harpin were also induced by ethylene. Analysis of mutant plants further demonstrated that ethylene signaling, but not salicylic acid or jasmonate signaling, was required for the harpin response. Finally, analysis of plants with mutations in genes encoding two components of the ethylene pathway, EIN2 or EIN5, indicated that EIN2 was required for aphid resistance, whereas EIN5 was required for plant growth enhancement. These results provide insight into the molecular mechanisms by which ethylene can control diverse plant responses.
H.-P. Dong. J. Peng, Z. Bao, X. Meng, J. M. Bonasera, G. Chen, S. V. Beer, H. Dong, Downstream divergence of the ethylene signaling pathway for harpin-stimulated Arabidopsis growth and insect defense. Plant Phys. 136, 3628-3638 (2004). [Abstract] [Full Text]