Phenylalanine ammonia-lyase inhibitors do not prevent russet spotting lesion development in lettuce midribs
1998
A:PS
Details
Title
Phenylalanine ammonia-lyase inhibitors do not prevent russet spotting lesion development in lettuce midribs
Publication Date
1998
Call Number
A:PS
Summary
Russet spotting is a physiological disorder of lettuces caused by exposure to hormonal levels (<1 ?/litre) of ethylene in air at _5?. Enhanced phenolic metabolism and the accumulation of phenolic compounds accompany the appearance of brown, oval lesions on the leaf midrib. Phenylalanine ammonia-lyase (PAL) is the first committed enzyme in the phenylpropanoid pathway. Three inhibitors of PAL activity (2-aminoindan-2-phosphonic acid (AIP), alpha-aminooxyacetic acid (AOA), and alpha-aminooxi-beta-phenylpropionic acid (AOPP)) greatly reduced the accumulation of phenolic compounds and browning of lesions. At 50 ?, AIP inhibited the formation of chlorogenic and dicaffeoyl tartaric acids in cut midribs of iceberg lettuce by 92 and 98%, respectively. AIP competitively inhibited PAL activity from a lettuce midrib homogenate with an apparent Ki of 22 nM. While the formation of phenolic compounds was strongly inhibited by AIP, the number of lesions associated with russet spotting was not affected. Only the colour of the lesions was affected by AIP. In control midribs, the russet spotting lesions were brown, while those in the AIP-treated midribs were initially olive green. After 3-7 days, these lesions also turned brown. No tyrosine ammonia-lyase activity was detected in a homogenate of lettuce midrib tissue. It is suggested that the early development of russet spotting lesions is independent of the increase in PAL activity and phenolic compounds. However, accumulation of phenolic compounds does contribute to the subsequent browning symptoms indicative of russet spotting.
Journal Citation
v.123(4):687-691, AMERICAN SOCIETY FOR HORTICULTURAL SCIENCE, JOURNAL
Contact Information
harvest@worldveg.org
Record Appears in
Research > Published Articles