Evaluating potential plant hormone cross talk between auxin and ethylene in Arabidopsis

Auxin is the primary hormone responsible for plant growth and development. Regulation of auxin-response genes occurs through transcriptional activators (auxin response factors called ARFs) which bind to auxin response elements (AuxREs). Some auxin-responsive genes encode aminocyclopropane-1-carboxylic acid synthase (ACS) enzymes which regulate the production of the plant hormone ethylene. The major research objective was to evaluate transcriptional cross talk between auxin and ethylene. Both AuxREs and ethylene response elements were found in several ACS and ARF genes, suggesting cross talk between the two hormones at the transcriptional level. Analysis of transgenic Arabidopsis thaliana plants deficient in ARF7 and contain a reporter gene for the ACS5 expression were used to evaluate cross talk supports ARF7 regulation of ACS5 expression after auxin treatment in dark-grown seedlings and during flower development in light-grown seedlings, but do not show a strong association with gravitropism and wounding responses.