An auxin-regulated calmodulin cDNA (arCaM) were isolated by differential screening from a mung bean (Vigna radiata) cDNA library. The expression of the arCaM transcript in the etiolated mung bean hypocotyl was examined by RNA gel blot analysis. The arCaM transcript was induced depending on indole-3-acetic acid (IAA) concentrations. An increase in level of the arCaM transcript upon treatment of hypocotyl segments with 10 microM IAA was detected after 1 h and a maximum level was detected at 2 h. Induction of the arCaM transcript occurred upon treatment with 10 microM 2,4-dichlorophenoxyacetic acid (2,4-D) or naphthalene-1-acetic acid (NAA) as well as with IAA, while treatment with 10 microM p-chlorophenoxyisobutyric acid (PCIB) as an anti-auxin, prevented the induction. Ethylene did not have any effect. Other stress conditions, such as exposure to salt stress, heavy metal ions and heat shock, also had no effect on the induction. The levels of the arCaM transcript in leaves of light-grown mung bean plants treated with IAA showed steady but small increases with time.