A proteomic analysis identifies glutathione S-transferase isoforms whose abundance is differentially regulated by ethylene during the formation of early root epidermis in Arabidopsis seedlings.

The plant hormone ethylene has been shown to play an important role in root hair development in Arabidopsis. With the aid of proteomic analysis, we identified three distinct glutathione S-transferase (GST) isoforms, AtGSTF2, AtGSTF8, and AtGSTU19, expressed early in root epidermal establishment in Arabidopsis seedlings. The AtGSTF2 protein was specifically up-regulated by ethylene. A subsequent RNA expression study revealed that the AtGSTF2 gene was highly sensitive to ethylene, whereas the transcripts for AtGSTF8 and AtGSTU19 were constitutively present in new root tissue of 4-day-old seedlings. The steady-state level of AtGSTF2 mRNA was greatly reduced in the roots of ethylene-insensitive mutants, while mutation at the CTR1 locus, which confers an ectopic root hair phenotype, resulted in a markedly elevated level of AtGSTF2 transcript in young root tissue. Although the physiological function of ethylene-induced AtGSTF2 is not yet clear, there are several possibilities for its role during early root development.