XVI International Botanical Congess
To understand the molecular regulation of ethylene production by touch stimuli, we examined the expression of ACS isogenes in tomato plant. Touch stimulation of 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.