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Heat shock treatments delay the increase in wound‐induced phenylalanine ammonia‐lyase activity by altering its expression, not its induction in Romaine lettuce ( Lactuca sativa ) tissue
Author(s) -
CamposVargas Reinaldo,
ogaki Hiroyuki,
Suslow Trevor,
Saltveit Mikal E.
Publication year - 2005
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.2005.00446.x
Subject(s) - lactuca , phenylalanine ammonia lyase , complementary dna , microbiology and biotechnology , biochemistry , protein biosynthesis , enzyme assay , heat shock protein , enzyme , biology , blot , messenger rna , phenylalanine , gene expression , botany , gene , amino acid
Wounding lettuce ( Lactuca sativa L., var. Longifolia) leaves induced an eight‐fold increase in the activity of phenylalanine ammonia‐lyase (PAL; EC 4.3.1.5), and the subsequent accumulation of phenolic compounds and tissue browning at 10°C. PAL is a key enzyme in the synthesis of phenolic compounds. A PAL cDNA was previously isolated by reverse‐transcription PCR using total RNA from wounded lettuce leaves. RNA gel blots showed that maximum accumulation of both PAL mRNA and PAL enzyme activity occurred 24 h after wounding. A 2‐min heat shock at 45°C administered within 5 min of wounding delayed the wound‐induced increase in PAL activity, but did not delay the increase in wound‐induced PAL mRNA. Changes in the content of PAL protein were also followed by immunoblot using anti‐PAL antibody raised against the bacterially expressed protein from the cDNA. Immunoblots showed that the level of PAL protein in wounded lettuce tissue was significantly reduced by the heat shock treatment. These data suggest that heat shock reduces the rise in wound‐induced PAL enzyme activity by reducing the translation of wound‐induced PAL mRNA, or by increasing the turnover of the induced PAL protein.