Rapid and Transient Expression of 1-Aminocyclopropane-1-Carboxylate Synthase Isogenes by Touch and Wound Stimuli in Tomato

Abstract

Touch stimuli induce ethylene production from 1-aminocyclopropane-1-carboxylic acid (ACC) in various plant species. We attempted to determine which ACC synthase (ACS) isogenes play a role in this phenomenon. We isolated cDNA clones (LE-ACS1A, 1B, 2, 3, 4 and 6) for ACC synthase isogenes from tomato, and their expressions were examined. Touch stimulation of tomato seedlings and fruits led to a large increase in the levels of LE-ACS6 and LE-ACS1A mRNA transcripts. The expressions of LE-ACS6 and LE-ACS1A isogenes increased within 10 min after touch, and mRNAs for both genes disappeared by 2 h. Thus, their expressions are transient. Wounding of tomato leaves and fruits also gave rise to transient expressions of LE-ACS6 and LE-ACS1A. The mRNA of the LE-ACS2 gene, a wound-inducible gene, was detected after 2 h in wounded tissues, but not in touched tissues. The results clearly indicate that the two isogenes, LE-ACS6 and LE-ACS1A, sense only touch, contact or pressure, and that another isogene, LE-ACS2, requires severe cell damage for its expression.